The Pittcon 2012 Organizing Committee is pleased to announce that this year’s conference and exposition for laboratory science attracted15,754 attendees (conferees and exhibitor personnel) to the annual event, which was held in Orlando, Florida, March 11-15. Twenty-nine percent of the conferees were from 89 countries outside the United States. A detailed summary of attendance is available at http://www.pittcon.org.
Pittcon 2012 President Jon Peace commented, “In a time where economic changes, increased mergers and acquisitions, and rising travel costs have a substantial impact on conferences, attendees still consider Pittcon to be a most valuable educational and networking resource for the global scientific community.”
This blog has been set up for editors, reviewers, authors and readers of Elsevier's Analytical Chemistry Journals - all of which can be seen below. It will be updated from Monday to Friday with general news and announcements concerning the titles listed on this page. It should be noted that the views or claims made in the news items and feeds are not necessarily those of the Publisher.
World Congress on Biosensors 2014
Biosensors 2014
Friday, 30 March 2012
Direct visualisation of cell organelle or sub-cellular structure in real time
AMSBIO has announced a new range of ready-to-use lentiviral particles that
allow direct visualisation of organelles or structures in cells without
manipulation.
For real time visualisation, traditionally researchers have had to use plasmids for organelle markers, but the labelling was transitory. Now using the new AMSBIO lentiviral particles - researchers have an easy way to provide long term labels on many cellular structures (stable integration inside the genome) without the need for transfection reagents. Using lentiviral particles also allows effective direct visualisation of Nuclei, Nuclear Membrane, Mitotic Chromosomes and Interphase Chromatin, Endosome, Endoplasmic Reticulum, Microtubule, Mitochondria, Golgi, Lysosome, Plasma Membrane, Cytoplasm and Peroxisome in hard to transfect mammalian cells, stem cells and primary cells.
The new lentiviral particles employ 3 fluorescent protein tags (GFP, RFP or CFP), fused to specific DNAs encoding organelle-specific or structure-specific proteins, to enable direct visualization of the organelles or structures without manipulation or antibodies. Using this proprietary multicolour labelling technology - researchers can now target 3 different structures in the same experiment and differentiate them from each other easily.
For further information visit www.amsbio.com/Lentivirus.aspx or contact AMSBIO on tel. +44-1235-828200 or email dominiquef@amsbio.com.
For real time visualisation, traditionally researchers have had to use plasmids for organelle markers, but the labelling was transitory. Now using the new AMSBIO lentiviral particles - researchers have an easy way to provide long term labels on many cellular structures (stable integration inside the genome) without the need for transfection reagents. Using lentiviral particles also allows effective direct visualisation of Nuclei, Nuclear Membrane, Mitotic Chromosomes and Interphase Chromatin, Endosome, Endoplasmic Reticulum, Microtubule, Mitochondria, Golgi, Lysosome, Plasma Membrane, Cytoplasm and Peroxisome in hard to transfect mammalian cells, stem cells and primary cells.
The new lentiviral particles employ 3 fluorescent protein tags (GFP, RFP or CFP), fused to specific DNAs encoding organelle-specific or structure-specific proteins, to enable direct visualization of the organelles or structures without manipulation or antibodies. Using this proprietary multicolour labelling technology - researchers can now target 3 different structures in the same experiment and differentiate them from each other easily.
For further information visit www.amsbio.com/Lentivirus.aspx or contact AMSBIO on tel. +44-1235-828200 or email dominiquef@amsbio.com.
Flip Cap Centrifuge Tubes
Porvair Sciences has introduced a new range of high grade polypropylene flip
cap centrifuge tubes that combine ease of use, chemical resistance and high
speed tolerance.
Designed for easy one-handed operation the secure leak proof flip cap lid on each centrifuge tube can also be unscrewed. Available in a range of standard sizes the dimensions of Porvair flip cap centrifuge tubes are compatible with almost all centrifuge rotors. Affordably priced - Porvair flip cap centrifuge tubes can be spun up to 9400G and will withstand repeated autoclaving at 121C or long term storage at -80C. For easy identification each centrifuge tube has a solvent resistant writing area.
Porvair 15ml and 50ml flip cap centrifuge tubes have thin clear polypropylene walls and can withstand 8000G and 12000G respectively. Self-standing centrifuge tubes are available in the popular 50ml size with conical bottoms and an outer collar that allows the tube to stand on a bench and can withstand 6000G.
Production of Porvair flip cap centrifuge tubes is carried out in a Class 10000 / ISO Class VII clean environment to ISO 9001:2008 and EN ISO 13485:2003 manufacturing standards to ensure all products are free from DNA/RNA, DNase/RNase and Pyrogen contamination. Porvair centrifuge tubes are supplied gamma irradiated sterile packaged in zip sealed bags.
Established in 1992, Porvair Sciences Ltd. expertise in microplate technology and manufacturing covers scientific fields including Life Sciences, Drug Discovery, Combinatorial Chemistry, Solid Phase Extraction, Protein Purification, High Throughput Screening, Proteomics and Genomics. Porvair Sciences Ltd. is a wholly owned subsidiary of Porvair plc.
For further information on the flip cap centrifuge tubes please contact Porvair Sciences on telephone +44-1372-824290, email int.sales@porvair-sciences.com or visit the website at www.epigeneticsexpress.com
Designed for easy one-handed operation the secure leak proof flip cap lid on each centrifuge tube can also be unscrewed. Available in a range of standard sizes the dimensions of Porvair flip cap centrifuge tubes are compatible with almost all centrifuge rotors. Affordably priced - Porvair flip cap centrifuge tubes can be spun up to 9400G and will withstand repeated autoclaving at 121C or long term storage at -80C. For easy identification each centrifuge tube has a solvent resistant writing area.
Porvair 15ml and 50ml flip cap centrifuge tubes have thin clear polypropylene walls and can withstand 8000G and 12000G respectively. Self-standing centrifuge tubes are available in the popular 50ml size with conical bottoms and an outer collar that allows the tube to stand on a bench and can withstand 6000G.
Production of Porvair flip cap centrifuge tubes is carried out in a Class 10000 / ISO Class VII clean environment to ISO 9001:2008 and EN ISO 13485:2003 manufacturing standards to ensure all products are free from DNA/RNA, DNase/RNase and Pyrogen contamination. Porvair centrifuge tubes are supplied gamma irradiated sterile packaged in zip sealed bags.
Established in 1992, Porvair Sciences Ltd. expertise in microplate technology and manufacturing covers scientific fields including Life Sciences, Drug Discovery, Combinatorial Chemistry, Solid Phase Extraction, Protein Purification, High Throughput Screening, Proteomics and Genomics. Porvair Sciences Ltd. is a wholly owned subsidiary of Porvair plc.
For further information on the flip cap centrifuge tubes please contact Porvair Sciences on telephone +44-1372-824290, email int.sales@porvair-sciences.com or visit the website at www.epigeneticsexpress.com
Thursday, 29 March 2012
Just Published: Journal of Chromatography A
A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Selected
papers from the latest issue:
Low-density solvent based ultrasound-assisted emulsification microextraction and on-column derivatization combined with gas chromatography–mass spectrometry for the determination of carbamate pesticides in environmental water samples
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Liang Guo, Hian Kee Lee
A fast and efficient method for the determination of trace level of carbamate pesticides using a lower-density-than-water solvent for ultrasound-assisted emulsification microextraction coupled to on-column derivatization and analysis by GC–MS has been developed and studied. In this approach, a soft plastic Pasteur pipette was employed as a convenient extraction device. Fifty microliters of extraction solvent, of lower density than water, was injected into the sample solution held in the pipette. The latter was immediately immersed in an ultrasound water bath to form an emulsion. After 2min extraction, the emulsion was fractionated into two layers by centrifugation. The upper layer (organic extract) could be collected conveniently by squeezing the bulb of the pipette, now held upside down, to move it into the narrow stem of the device, facilitating its retrieval for analysis. The extract was then combined with trimethylphenylammonium hydroxide and directly injected into a gas chromatography–mass spectrometry (GC–MS) system for on-column derivatization and analysis. The on-column derivatization provided an added convenience (since a separate step was not necessary). Parameters affecting the derivatization and extraction were investigated. Under the most favorable conditions, the method demonstrated high extraction efficiency with low limits of detection of between 0.01 and 0.1μg/L, good linearity in the range of 0.05–50μg/L, to 0.5–100μg/L, and good repeatability (RSD below 9.2%, n =5). The proposed method was evaluated by determining carbamate pesticides in river water samples.
Source:Journal of Chromatography A, Volume 1235
Liang Guo, Hian Kee Lee
A fast and efficient method for the determination of trace level of carbamate pesticides using a lower-density-than-water solvent for ultrasound-assisted emulsification microextraction coupled to on-column derivatization and analysis by GC–MS has been developed and studied. In this approach, a soft plastic Pasteur pipette was employed as a convenient extraction device. Fifty microliters of extraction solvent, of lower density than water, was injected into the sample solution held in the pipette. The latter was immediately immersed in an ultrasound water bath to form an emulsion. After 2min extraction, the emulsion was fractionated into two layers by centrifugation. The upper layer (organic extract) could be collected conveniently by squeezing the bulb of the pipette, now held upside down, to move it into the narrow stem of the device, facilitating its retrieval for analysis. The extract was then combined with trimethylphenylammonium hydroxide and directly injected into a gas chromatography–mass spectrometry (GC–MS) system for on-column derivatization and analysis. The on-column derivatization provided an added convenience (since a separate step was not necessary). Parameters affecting the derivatization and extraction were investigated. Under the most favorable conditions, the method demonstrated high extraction efficiency with low limits of detection of between 0.01 and 0.1μg/L, good linearity in the range of 0.05–50μg/L, to 0.5–100μg/L, and good repeatability (RSD below 9.2%, n =5). The proposed method was evaluated by determining carbamate pesticides in river water samples.
Smart polymer mediated purification and recovery of active proteins from inclusion bodies
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Saurabh Gautam, Priyanka Dubey, Pranveer Singh, S. Kesavardhana, Raghavan Varadarajan, Munishwar N. Gupta
Obtaining correctly folded proteins from inclusion bodies of recombinant proteins expressed in bacterial hosts requires solubilization with denaturants and a refolding step. Aggregation competes with the second step. Refolding of eight different proteins was carried out by precipitation with smart polymers. These proteins have different molecular weights, different number of disulfide bridges and some of these are known to be highly prone to aggregation. A high throughput refolding screen based upon fluorescence emission maximum around 340nm (for correctly folded proteins) was developed to identify the suitable smart polymer. The proteins could be dissociated and recovered after the refolding step. The refolding could be scaled up and high refolding yields in the range of 8mgL−1 (for CD4D12, the first two domains of human CD4) to 58mgL−1 (for malETrx, thioredoxin fused with signal peptide of maltose binding protein) were obtained. Dynamic light scattering (DLS) showed that polymer if chosen correctly acted as a pseudochaperonin and bound to the proteins. It also showed that the time for maximum binding was about 50min which coincided with the time required for incubation (with the polymer) before precipitation for maximum recovery of folded proteins. The refolded proteins were characterized by fluorescence emission spectra, circular dichroism (CD) spectroscopy, melting temperature (T m), and surface hydrophobicity measurement by ANS (8-anilino1-naphthalene sulfonic acid) fluorescence. Biological activity assay for thioredoxin and fluorescence based assay in case of maltose binding protein (MBP) were also carried out to confirm correct refolding.
Source:Journal of Chromatography A, Volume 1235
Saurabh Gautam, Priyanka Dubey, Pranveer Singh, S. Kesavardhana, Raghavan Varadarajan, Munishwar N. Gupta
Obtaining correctly folded proteins from inclusion bodies of recombinant proteins expressed in bacterial hosts requires solubilization with denaturants and a refolding step. Aggregation competes with the second step. Refolding of eight different proteins was carried out by precipitation with smart polymers. These proteins have different molecular weights, different number of disulfide bridges and some of these are known to be highly prone to aggregation. A high throughput refolding screen based upon fluorescence emission maximum around 340nm (for correctly folded proteins) was developed to identify the suitable smart polymer. The proteins could be dissociated and recovered after the refolding step. The refolding could be scaled up and high refolding yields in the range of 8mgL−1 (for CD4D12, the first two domains of human CD4) to 58mgL−1 (for malETrx, thioredoxin fused with signal peptide of maltose binding protein) were obtained. Dynamic light scattering (DLS) showed that polymer if chosen correctly acted as a pseudochaperonin and bound to the proteins. It also showed that the time for maximum binding was about 50min which coincided with the time required for incubation (with the polymer) before precipitation for maximum recovery of folded proteins. The refolded proteins were characterized by fluorescence emission spectra, circular dichroism (CD) spectroscopy, melting temperature (T m), and surface hydrophobicity measurement by ANS (8-anilino1-naphthalene sulfonic acid) fluorescence. Biological activity assay for thioredoxin and fluorescence based assay in case of maltose binding protein (MBP) were also carried out to confirm correct refolding.
One step solvent bar microextraction and derivatization followed by gas chromatography–mass spectrometry for the determination of pharmaceutically active compounds in drain water samples
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Liang Guo, Hian Kee Lee
For the first time, a simple and novel one-step combined solvent bar microextraction with derivatization with GC–MS analysis, was developed for the determination of pharmaceutically active compounds (PhACs) in water samples. In the procedure, the derivatization reagent was added in the extraction solvent (solvent bar), so that the analytes could be extracted from the aqueous sample and simultaneously derivatized in the solvent bar to enhance their volatility and improve chromatographic performance. After extraction, the derivatized analytes in the extract were directly injected into a GC–MS system for analysis. Six PhACs including naproxen, ibuprofen, ketoprofen, propranolol, diclofenac, and alprenolol were used here to develop and evaluate the method. The parameters affecting the derivatization and extraction efficiency including derivatization time and temperature, the proportion of derivatization reagent, the type of organic solvent, extraction time, extraction temperature, pH of sample solution, effect of ionic strength, and sample agitation speed, were investigated in detail. Under the most favorable conditions, the method provided good limits of detection ranging from 0.006 to 0.022μg/L, linearity (from 0.1–50 to 0.2–50μg/L, depending on analytes) and repeatability of extractions (RSDs below 9.5%, n =5). The proposed method was compared to hollow fiber protected liquid-phase microextraction and solid-phase microextraction, and showed higher extraction efficiency and/or shorter extraction time. The proposed method was applied to the determination of six PhACs in drain water, and was demonstrated to be simple, fast and efficient.
Source:Journal of Chromatography A, Volume 1235
Liang Guo, Hian Kee Lee
For the first time, a simple and novel one-step combined solvent bar microextraction with derivatization with GC–MS analysis, was developed for the determination of pharmaceutically active compounds (PhACs) in water samples. In the procedure, the derivatization reagent was added in the extraction solvent (solvent bar), so that the analytes could be extracted from the aqueous sample and simultaneously derivatized in the solvent bar to enhance their volatility and improve chromatographic performance. After extraction, the derivatized analytes in the extract were directly injected into a GC–MS system for analysis. Six PhACs including naproxen, ibuprofen, ketoprofen, propranolol, diclofenac, and alprenolol were used here to develop and evaluate the method. The parameters affecting the derivatization and extraction efficiency including derivatization time and temperature, the proportion of derivatization reagent, the type of organic solvent, extraction time, extraction temperature, pH of sample solution, effect of ionic strength, and sample agitation speed, were investigated in detail. Under the most favorable conditions, the method provided good limits of detection ranging from 0.006 to 0.022μg/L, linearity (from 0.1–50 to 0.2–50μg/L, depending on analytes) and repeatability of extractions (RSDs below 9.5%, n =5). The proposed method was compared to hollow fiber protected liquid-phase microextraction and solid-phase microextraction, and showed higher extraction efficiency and/or shorter extraction time. The proposed method was applied to the determination of six PhACs in drain water, and was demonstrated to be simple, fast and efficient.
Application of step-wise gradient high-performance counter-current chromatography for rapid preparative separation and purification of diterpene components from Pseudolarix kaempferi Gordon
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Shichao He, Shucai Li, Jianhong Yang, Haoyu Ye, Shijie Zhong, Hang Song, Yongkui Zhang, Cheng Peng, Aihua Peng, Lijuan Chen
In general, simultaneously separation and purification of components with a broad polarity range from traditional Chinese medicine (TCM) is a challenge by an ordinary high-speed counter-current chromatography (HSCCC) method. In this paper, we describes a rapid and efficient separation method of combining three-step gradient elution and two-step flow-rate gradient elution using high-performance counter-current chromatography (HPCCC) to separate 8 diterpene compounds simultaneously within 80min in a single run from the alcohol extract of Pseudolarix kaempferi Gordon. This separation process produced 166mg pseudolaric acid B O-β-d-glucopyranoside (PABGly), 152mg pseudolaric acid C (PAC), 8mg deacetylpseudolaric acid A (deacetylPAA), 5mg pseudolaric acid A O-β-d-glucopyranoside (PAAGly), 484mg pseudolaric acid B (PAB), 33mg pseudolaric acid B methyl ester (PAB methyl ester), 10mg pseudolaric acid A (PAA) and 18mg pseudolaric acid H (PAH) from 1.0g crude sample with purities of 98.6%, 99.6%, 92.3%, 92.2%, 99.2%, 99.4%, 98.3%, 91.0%, respectively. Our study indicates that the suitable combination of step-wise gradient elution and flow-rate gradient elution using HPCCC is an effective strategy to separate complex components from natural products.
Source:Journal of Chromatography A, Volume 1235
Shichao He, Shucai Li, Jianhong Yang, Haoyu Ye, Shijie Zhong, Hang Song, Yongkui Zhang, Cheng Peng, Aihua Peng, Lijuan Chen
In general, simultaneously separation and purification of components with a broad polarity range from traditional Chinese medicine (TCM) is a challenge by an ordinary high-speed counter-current chromatography (HSCCC) method. In this paper, we describes a rapid and efficient separation method of combining three-step gradient elution and two-step flow-rate gradient elution using high-performance counter-current chromatography (HPCCC) to separate 8 diterpene compounds simultaneously within 80min in a single run from the alcohol extract of Pseudolarix kaempferi Gordon. This separation process produced 166mg pseudolaric acid B O-β-d-glucopyranoside (PABGly), 152mg pseudolaric acid C (PAC), 8mg deacetylpseudolaric acid A (deacetylPAA), 5mg pseudolaric acid A O-β-d-glucopyranoside (PAAGly), 484mg pseudolaric acid B (PAB), 33mg pseudolaric acid B methyl ester (PAB methyl ester), 10mg pseudolaric acid A (PAA) and 18mg pseudolaric acid H (PAH) from 1.0g crude sample with purities of 98.6%, 99.6%, 92.3%, 92.2%, 99.2%, 99.4%, 98.3%, 91.0%, respectively. Our study indicates that the suitable combination of step-wise gradient elution and flow-rate gradient elution using HPCCC is an effective strategy to separate complex components from natural products.
Pareto-optimality study into the comparison of the separation potential of comprehensive two-dimensional liquid chromatography in the column and spatial modes
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Dominique J.D. Vanhoutte, Gabriel Vivó-Truyols, Peter J. Schoenmakers
The expected performance of spatial (“flat-bed”) two-dimensional liquid chromatography ( x LC× x LC) has been calculated using the Pareto-optimality strategy. This approach allowed different objectives (total peak capacity, total analysis time, and total dilution) to be considered simultaneously and to establish optimal parameters (pressure drop, particle size, bed length, and initial spot size). The performance of spatial two-dimensional chromatographic systems was compared with that of conventional on-line, real-time two-dimensional column-liquid-chromatography systems ( t LC× t LC). The potential gain in peak capacity and/or analysis time of the spatial configuration was confirmed. By restricting the spatial parameters to realistic chromatographic conditions (limiting the stress, as counterbalance for the pressure drop through the sorbent bed, to 2500kg) it was found that x LC× x LC is attractive for very fast analysis of complex samples, rather than for extremely efficient separations. For example, a peak capacity of 780 may be achieved in only 2.7min using a 100×100mm sorbent bed of a quality currently encountered thin-layer chromatography. Furthermore, if beds can be packed as efficiently as contemporary columns, the predicted peak capacity increases to around 1000, corresponding to a peak-production rate of about 6.3peaks/s. Possibilities to boost the performance of x LC× x LC further are briefly discussed. Unless we can overcome the severe stress requirements of high-performance x LC× x LC, conventional t LC× t LC may be more amenable to very complex separations, thanks to the very high peak capacities. However, t LC× t LC separations will require long analysis times (e.g. 10,000 peaks in 37h, corresponding to 0.075peaks/s at a pressure drop of 40MPa). The best trade-off between total peak capacity, total analysis time, and total dilution under restricted (realistic) conditions was obtained using high pressures, small chromatographic beds, small particles, and relatively large sample spots.
Source:Journal of Chromatography A, Volume 1235
Dominique J.D. Vanhoutte, Gabriel Vivó-Truyols, Peter J. Schoenmakers
The expected performance of spatial (“flat-bed”) two-dimensional liquid chromatography ( x LC× x LC) has been calculated using the Pareto-optimality strategy. This approach allowed different objectives (total peak capacity, total analysis time, and total dilution) to be considered simultaneously and to establish optimal parameters (pressure drop, particle size, bed length, and initial spot size). The performance of spatial two-dimensional chromatographic systems was compared with that of conventional on-line, real-time two-dimensional column-liquid-chromatography systems ( t LC× t LC). The potential gain in peak capacity and/or analysis time of the spatial configuration was confirmed. By restricting the spatial parameters to realistic chromatographic conditions (limiting the stress, as counterbalance for the pressure drop through the sorbent bed, to 2500kg) it was found that x LC× x LC is attractive for very fast analysis of complex samples, rather than for extremely efficient separations. For example, a peak capacity of 780 may be achieved in only 2.7min using a 100×100mm sorbent bed of a quality currently encountered thin-layer chromatography. Furthermore, if beds can be packed as efficiently as contemporary columns, the predicted peak capacity increases to around 1000, corresponding to a peak-production rate of about 6.3peaks/s. Possibilities to boost the performance of x LC× x LC further are briefly discussed. Unless we can overcome the severe stress requirements of high-performance x LC× x LC, conventional t LC× t LC may be more amenable to very complex separations, thanks to the very high peak capacities. However, t LC× t LC separations will require long analysis times (e.g. 10,000 peaks in 37h, corresponding to 0.075peaks/s at a pressure drop of 40MPa). The best trade-off between total peak capacity, total analysis time, and total dilution under restricted (realistic) conditions was obtained using high pressures, small chromatographic beds, small particles, and relatively large sample spots.
A comparison of overload behaviour for some sub 2μm totally porous and sub 3μm shell particle columns with ionised solutes
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Morgane M. Fallas, Stephan M.C. Buckenmaier, David V. McCalley
The overloading performance of some 2.7μm shell and sub 2μm totally porous columns, including one pair manufactured from similar materials with similar bonding chemistries, was compared using strongly acidic and basic probe compounds. In general, the capacity of shell particles was not greatly reduced, despite containing a smaller porous volume. Nevertheless, at low pH, both types of column were overloaded by only small concentrations of ionised solute. Considerable improvement could be gained by increasing the buffer concentration, although sensitivity in mass spectrometric detection may be compromised. The capacity of columns of different internal diameter may not be directly compared merely by scaling the injection volumes, as it is possible that the sample is not homogeneously distributed across the column radius, especially in larger diameter columns, where the sample may travel preferentially through a central core of the packing. A totally porous charged surface hybrid phase gave much improved loading properties of the basic probe in low ionic strength mobile phases such as formic acid, often used in mass spectrometry. However, its relative advantage over conventional phases was reduced as the mobile phase ionic strength was increased. Furthermore, acidic compounds may give tailing on this phase. At pH 7, all columns tested showed evidence of interaction with ionised silanols; peak shapes improved as the buffer concentration was increased. Column efficiency first increased and then decreased as solute concentration was increased at constant buffer concentration, which can be attributed to the decreasing proportion of solute molecules retained by the ion exchange process.
Source:Journal of Chromatography A, Volume 1235
Morgane M. Fallas, Stephan M.C. Buckenmaier, David V. McCalley
The overloading performance of some 2.7μm shell and sub 2μm totally porous columns, including one pair manufactured from similar materials with similar bonding chemistries, was compared using strongly acidic and basic probe compounds. In general, the capacity of shell particles was not greatly reduced, despite containing a smaller porous volume. Nevertheless, at low pH, both types of column were overloaded by only small concentrations of ionised solute. Considerable improvement could be gained by increasing the buffer concentration, although sensitivity in mass spectrometric detection may be compromised. The capacity of columns of different internal diameter may not be directly compared merely by scaling the injection volumes, as it is possible that the sample is not homogeneously distributed across the column radius, especially in larger diameter columns, where the sample may travel preferentially through a central core of the packing. A totally porous charged surface hybrid phase gave much improved loading properties of the basic probe in low ionic strength mobile phases such as formic acid, often used in mass spectrometry. However, its relative advantage over conventional phases was reduced as the mobile phase ionic strength was increased. Furthermore, acidic compounds may give tailing on this phase. At pH 7, all columns tested showed evidence of interaction with ionised silanols; peak shapes improved as the buffer concentration was increased. Column efficiency first increased and then decreased as solute concentration was increased at constant buffer concentration, which can be attributed to the decreasing proportion of solute molecules retained by the ion exchange process.
Study of the retention behavior in zwitterionic hydrophilic interaction chromatography of isomeric hydroxy- and aminobenzoic acids
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Giorgia Greco, Sylvia Grosse, Thomas Letzel
The retention behavior of fifteen isomeric hydroxy- and aminobenzoic acids in zwitterionic hydrophilic interaction chromatography was studied using a sulfobetaine phase (ZIC-HILIC). By an inspection of their molecular structures, the retention was related to the number, the position and hydrogen bond properties of the functional groups. The effect of the chromatographic conditions was analyzed in order to investigate the retention mechanism of the stationary phase. The increased retention observed for negative charged compounds when the mobile phase pH decreased was ascribed to a diminishing of the electrostatic repulsion with the underivatized silanol groups. Also the salt buffer concentration in the mobile was proved to have a great influence in the modulation of the electrostatic interactions. However, the retention behavior of the benzoic acids was not described by conventional ion-exchange models. Subsequently, a systematical analysis of partition, adsorption, and hydrophilic chromatographic models was presented. The results from the fittings indicated that partition processes govern mainly the ZIC-HILIC separation, but also adsorption processes via hydrogen bonds occurred for hydrogen donor analytes. Finally, the influence of the chromatographic conditions on the water enriched layer in which partition takes place has been evaluated by the elution behavior of toluene.
Source:Journal of Chromatography A, Volume 1235
Giorgia Greco, Sylvia Grosse, Thomas Letzel
The retention behavior of fifteen isomeric hydroxy- and aminobenzoic acids in zwitterionic hydrophilic interaction chromatography was studied using a sulfobetaine phase (ZIC-HILIC). By an inspection of their molecular structures, the retention was related to the number, the position and hydrogen bond properties of the functional groups. The effect of the chromatographic conditions was analyzed in order to investigate the retention mechanism of the stationary phase. The increased retention observed for negative charged compounds when the mobile phase pH decreased was ascribed to a diminishing of the electrostatic repulsion with the underivatized silanol groups. Also the salt buffer concentration in the mobile was proved to have a great influence in the modulation of the electrostatic interactions. However, the retention behavior of the benzoic acids was not described by conventional ion-exchange models. Subsequently, a systematical analysis of partition, adsorption, and hydrophilic chromatographic models was presented. The results from the fittings indicated that partition processes govern mainly the ZIC-HILIC separation, but also adsorption processes via hydrogen bonds occurred for hydrogen donor analytes. Finally, the influence of the chromatographic conditions on the water enriched layer in which partition takes place has been evaluated by the elution behavior of toluene.
Multi-wavelength high-performance liquid chromatographic fingerprints and chemometrics to predict the antioxidant activity of Turnera diffusa as part of its quality control
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
J. Ricardo Lucio-Gutiérrez, Aurora Garza-Juárez, J. Coello, S. Maspoch, M.L. Salazar-Cavazos, Ricardo Salazar-Aranda, Noemi Waksman de Torres
The determination of the antioxidant activity of Turnera diffusa using partial least squares regression (PLSR) on chromatographic data is presented. The chromatograms were recorded with a diode array detector and, for each sample, an enhanced fingerprint was constructed by compiling into a single data vector the chromatograms at four wavelengths (216, 238, 254 and 345nm). The wavelengths were selected from a contour plot, in order to obtain the greater number of peaks at each of the wavelengths. A further pretreatment of the data that included baseline correction, scaling and correlation optimized warping was performed. Optimal values of the parameters used in the warping were found by means of simplex optimization. A PLSR model with four latent variables (LV) explained 52.5% of X variance and 98.4% of Y, with a root mean square error for cross validation of 6.02. To evaluate its reliability, it was applied to an external prediction set, retrieving a relative standard error for prediction of 7.8%. The study of the most important variables for the regression indicated the chromatographic peaks related to antioxidant activity at the used wavelengths.
Source:Journal of Chromatography A, Volume 1235
J. Ricardo Lucio-Gutiérrez, Aurora Garza-Juárez, J. Coello, S. Maspoch, M.L. Salazar-Cavazos, Ricardo Salazar-Aranda, Noemi Waksman de Torres
The determination of the antioxidant activity of Turnera diffusa using partial least squares regression (PLSR) on chromatographic data is presented. The chromatograms were recorded with a diode array detector and, for each sample, an enhanced fingerprint was constructed by compiling into a single data vector the chromatograms at four wavelengths (216, 238, 254 and 345nm). The wavelengths were selected from a contour plot, in order to obtain the greater number of peaks at each of the wavelengths. A further pretreatment of the data that included baseline correction, scaling and correlation optimized warping was performed. Optimal values of the parameters used in the warping were found by means of simplex optimization. A PLSR model with four latent variables (LV) explained 52.5% of X variance and 98.4% of Y, with a root mean square error for cross validation of 6.02. To evaluate its reliability, it was applied to an external prediction set, retrieving a relative standard error for prediction of 7.8%. The study of the most important variables for the regression indicated the chromatographic peaks related to antioxidant activity at the used wavelengths.
Thermodynamic study of molecularly imprinted polymer used as the stationary phase in high performance liquid chromatography
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Natalia Denderz, Jozef Lehotay, Jozef Čižmárik, Zuzana Cibulková, Peter Šimon
Molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) on the base of methacrylic acid prepared by a bulk polymerization were used as stationary phases for the HPLC analysis. The thermodynamic processes were carried out to investigate the temperature effects during sorption processes of potential local anaesthetics – morpholinoethyl esters of alkoxy-substituted phenylcarbamic acid (MEsP), local anaesthetic – diperodon, flavonoid – quercetin in methanol, acetonitrile and toluene (porogen) as mobile phases. Mobile phases and corresponding solvents were selected according to the solubility of each analyte. The template was chosen from the set of homologous of MEsP – 2-(morpholin-4-yl)ethyl (2-methoxyphenyl)carbamate. Values of retention factors were measured over the temperature range of 20–60°C. There were determined van’t Hoff curves – dependences between logarithms of the retention factors (ln k) and the inverse value of the temperature (1/T). Observed graphs were linear directly indicating that there were no changes of interaction mechanisms in the studied range of temperature. Selectivities (evaluated by the separation factors, α) and sorption selectivities (evaluated by the imprinting factors, IFs) of the MIP and the NIP toward template, related and not-related structures with the template were evaluated chromatographically. The highest separation factors and the imprinting factors (IF=4.73±0.35 for the template) were observed in methanol, not in porogen. Only in the case of quercetin the highest IF was observed in ACN (1.88±0.13). Contrary to expectations, the driving force for the affinity of the target molecules for both of polymers was enthalpic term (with an average of 54%, 82% and 84% contribution of enthalpic term for MeOH, ACN and toluene, respectively on the MIP and 53%, 57% and 65% for MeOH, ACN and toluene, respectively on the NIP). The MIP and NIP were also characterized by attenuated total reflectance analysis Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA).
Source:Journal of Chromatography A, Volume 1235
Natalia Denderz, Jozef Lehotay, Jozef Čižmárik, Zuzana Cibulková, Peter Šimon
Molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) on the base of methacrylic acid prepared by a bulk polymerization were used as stationary phases for the HPLC analysis. The thermodynamic processes were carried out to investigate the temperature effects during sorption processes of potential local anaesthetics – morpholinoethyl esters of alkoxy-substituted phenylcarbamic acid (MEsP), local anaesthetic – diperodon, flavonoid – quercetin in methanol, acetonitrile and toluene (porogen) as mobile phases. Mobile phases and corresponding solvents were selected according to the solubility of each analyte. The template was chosen from the set of homologous of MEsP – 2-(morpholin-4-yl)ethyl (2-methoxyphenyl)carbamate. Values of retention factors were measured over the temperature range of 20–60°C. There were determined van’t Hoff curves – dependences between logarithms of the retention factors (ln k) and the inverse value of the temperature (1/T). Observed graphs were linear directly indicating that there were no changes of interaction mechanisms in the studied range of temperature. Selectivities (evaluated by the separation factors, α) and sorption selectivities (evaluated by the imprinting factors, IFs) of the MIP and the NIP toward template, related and not-related structures with the template were evaluated chromatographically. The highest separation factors and the imprinting factors (IF=4.73±0.35 for the template) were observed in methanol, not in porogen. Only in the case of quercetin the highest IF was observed in ACN (1.88±0.13). Contrary to expectations, the driving force for the affinity of the target molecules for both of polymers was enthalpic term (with an average of 54%, 82% and 84% contribution of enthalpic term for MeOH, ACN and toluene, respectively on the MIP and 53%, 57% and 65% for MeOH, ACN and toluene, respectively on the NIP). The MIP and NIP were also characterized by attenuated total reflectance analysis Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA).
A simple and rapid extraction method for sensitive determination of perfluoroalkyl substances in blood serum suitable for exposure evaluation
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Noelia Luque, Ana Ballesteros-Gómez, Stefan van Leeuwen, Soledad Rubio
In this work, we propose a microextraction method based on a new supramolecular solvent (SUPRAS) made up of reverse aggregates of hexanoic acid, combined with liquid chromatography/triple quadrupole mass spectrometry (LC/QQQ MS–MS) for the determination of the perfluoroalkyl substances (PFASs) in blood serum. A SUPRAS is a nano-structured liquid made up of surfactant aggregates synthesized through a self-assembly process. The method involved the acidification of 765μL of blood serum (600μmol of hydrochloric acid per mL of serum) followed by the addition of hexanoic acid (97μL) and tetrahydrofuran (THF) (600μL), conditions under which the supramolecular solvent (∼360μL) formed in situ after vortex-shaking and centrifugation. Parameters affecting extraction efficiency and concentration factors were studied. The overall sample treatment took only 20min and several samples (20–30) can be simultaneously analyzed using conventional lab equipments, making additional investments unnecessary. Recoveries for the internal standards in samples ranged from 75 to 89% with relative standard deviations between 1 and 15%. Calibration was based on the use of internal standards. The method was very sensitive with detection limits ranging from 2 to 20pgmL−1 for PFASs. The approach developed was successfully applied to the determination of PFASs in different blood serum samples. The concentration of PFASs found in samples of animal origin ranged between 17 and 197.3pgmL−1 and between 84 and 5168pgmL−1 in samples of human origin. Both the analytical and operational features of this method make it suitable for the evaluation of exposure to PFASs.
Source:Journal of Chromatography A, Volume 1235
Noelia Luque, Ana Ballesteros-Gómez, Stefan van Leeuwen, Soledad Rubio
In this work, we propose a microextraction method based on a new supramolecular solvent (SUPRAS) made up of reverse aggregates of hexanoic acid, combined with liquid chromatography/triple quadrupole mass spectrometry (LC/QQQ MS–MS) for the determination of the perfluoroalkyl substances (PFASs) in blood serum. A SUPRAS is a nano-structured liquid made up of surfactant aggregates synthesized through a self-assembly process. The method involved the acidification of 765μL of blood serum (600μmol of hydrochloric acid per mL of serum) followed by the addition of hexanoic acid (97μL) and tetrahydrofuran (THF) (600μL), conditions under which the supramolecular solvent (∼360μL) formed in situ after vortex-shaking and centrifugation. Parameters affecting extraction efficiency and concentration factors were studied. The overall sample treatment took only 20min and several samples (20–30) can be simultaneously analyzed using conventional lab equipments, making additional investments unnecessary. Recoveries for the internal standards in samples ranged from 75 to 89% with relative standard deviations between 1 and 15%. Calibration was based on the use of internal standards. The method was very sensitive with detection limits ranging from 2 to 20pgmL−1 for PFASs. The approach developed was successfully applied to the determination of PFASs in different blood serum samples. The concentration of PFASs found in samples of animal origin ranged between 17 and 197.3pgmL−1 and between 84 and 5168pgmL−1 in samples of human origin. Both the analytical and operational features of this method make it suitable for the evaluation of exposure to PFASs.
Advanced ultra high pressure liquid chromatography–tandem mass spectrometric methods for the screening of red wine anthocyanins and derived pigments
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Philippus Alberts, Maria A. Stander, André de Villiers
Anthocyanins are responsible for the colour of red grapes and wine. In addition to their contribution to the sensory properties of wine, these compounds are also of interest due to their beneficial biological properties. Wine anthocyanins exhibit a large structural diversity due to variations in glycosylation and acylation patterns, which is further exacerbated by the diverse reactions involving grape-derived anthocyanins during wine ageing. Chromatographic as well as mass spectrometric resolution of wine anthocyanins is often precluded due to the complexity of these compounds. In this paper we report a rapid, high-efficiency ultra high pressure liquid chromatography (UHPLC) procedure with tandem mass spectrometric (MS/MS) detection for the in-depth screening of wine pigments. Selective detection of wine anthocyanins and derived pigments was achieved utilizing MS/MS in neutral loss scanning mode to observe the loss of dehydrated sugar moieties. This facilitated tentative compound identification based on molar mass information as well as the structured elution order of these compounds. In a second experiment, product ion spectra were recorded to allow identification of the anthocyanidin base using characteristic fragmentation patterns. The proposed methodology therefore involves two analyses for the sensitive and accurate identification of anthocyanins and their derived products in red wines. Mass spectra of wine anthocyanins under high energy collision induced dissociation (CID) conditions are reported, some for the first time. Significantly, chemical alteration of anthocyanins during wine ageing results in an off-set of the predominant fragments for each anthocyanidin base, whilst maintaining similar relative intensities. This allows unambiguous assignment of the derived products of anthocyanidin-glycosides. Using this approach, a total of 121 anthocyanins and derived compounds were identified in wines based on their relative reversed phase elution order as well as mass spectral information.
Source:Journal of Chromatography A, Volume 1235
Philippus Alberts, Maria A. Stander, André de Villiers
Anthocyanins are responsible for the colour of red grapes and wine. In addition to their contribution to the sensory properties of wine, these compounds are also of interest due to their beneficial biological properties. Wine anthocyanins exhibit a large structural diversity due to variations in glycosylation and acylation patterns, which is further exacerbated by the diverse reactions involving grape-derived anthocyanins during wine ageing. Chromatographic as well as mass spectrometric resolution of wine anthocyanins is often precluded due to the complexity of these compounds. In this paper we report a rapid, high-efficiency ultra high pressure liquid chromatography (UHPLC) procedure with tandem mass spectrometric (MS/MS) detection for the in-depth screening of wine pigments. Selective detection of wine anthocyanins and derived pigments was achieved utilizing MS/MS in neutral loss scanning mode to observe the loss of dehydrated sugar moieties. This facilitated tentative compound identification based on molar mass information as well as the structured elution order of these compounds. In a second experiment, product ion spectra were recorded to allow identification of the anthocyanidin base using characteristic fragmentation patterns. The proposed methodology therefore involves two analyses for the sensitive and accurate identification of anthocyanins and their derived products in red wines. Mass spectra of wine anthocyanins under high energy collision induced dissociation (CID) conditions are reported, some for the first time. Significantly, chemical alteration of anthocyanins during wine ageing results in an off-set of the predominant fragments for each anthocyanidin base, whilst maintaining similar relative intensities. This allows unambiguous assignment of the derived products of anthocyanidin-glycosides. Using this approach, a total of 121 anthocyanins and derived compounds were identified in wines based on their relative reversed phase elution order as well as mass spectral information.
Determination of N-methyl-1,3-propanediamine in bovine muscle by liquid chromatography with triple quadrupole and ion trap tandem mass spectrometry detection
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Clare Ho, Wai-On Lee, Yiu-Tung Wong
Morantel, pyrantel and their drug-related metabolites in food of animal-origin are regulated as sum of residues which may be hydrolysed to N-methyl-1,3-propanediamine (NMPA). In this study, an isotope dilution liquid chromatography tandem mass spectrometry (LC–MS/MS) method with pentafluoropropionic acid anhydride (PFPA) derivatization was developed for the determination of NMPA in bovine muscle. A stable isotope labeled internal standard N-methyl-d3-3,3′-d2-propane-1,3-diamine (NMPA-d5) was synthesized as internal standard. NMPA was derivatized with PFPA to form an N,N′-bis (pentafluoroacyl) derivative (NMPA-PFPA) and analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS/MS) and liquid chromatography ion trap mass spectrometry (LC-IT-MS/MS) using negative ion electrospray ionization (ESI). Chromatographic behavior of several perfluorocarboxylic acid anhydride derivatives of NMPA and other structurally related diamines on C-18 and perfluorophenyl (PFP) columns was studied. Conversion of the parent drugs to NMPA under various hydrolysis conditions was evaluated. In addition, comparison of the matrix effect and linearity with isotopically labeled internal standard (I.S.) and analogous I.S. were performed and investigated. The method was validated using fortified bovine muscle samples. The apparent recovery (obtained after correction with an isotopically labeled I.S.) was between 89% and 97% and repeatability was less than 10%. The lowest LOD and LOQ (0.42 and 1.39μg/kg, respectively) were obtained with LC-QqQ-MS/MS.
Source:Journal of Chromatography A, Volume 1235
Clare Ho, Wai-On Lee, Yiu-Tung Wong
Morantel, pyrantel and their drug-related metabolites in food of animal-origin are regulated as sum of residues which may be hydrolysed to N-methyl-1,3-propanediamine (NMPA). In this study, an isotope dilution liquid chromatography tandem mass spectrometry (LC–MS/MS) method with pentafluoropropionic acid anhydride (PFPA) derivatization was developed for the determination of NMPA in bovine muscle. A stable isotope labeled internal standard N-methyl-d3-3,3′-d2-propane-1,3-diamine (NMPA-d5) was synthesized as internal standard. NMPA was derivatized with PFPA to form an N,N′-bis (pentafluoroacyl) derivative (NMPA-PFPA) and analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS/MS) and liquid chromatography ion trap mass spectrometry (LC-IT-MS/MS) using negative ion electrospray ionization (ESI). Chromatographic behavior of several perfluorocarboxylic acid anhydride derivatives of NMPA and other structurally related diamines on C-18 and perfluorophenyl (PFP) columns was studied. Conversion of the parent drugs to NMPA under various hydrolysis conditions was evaluated. In addition, comparison of the matrix effect and linearity with isotopically labeled internal standard (I.S.) and analogous I.S. were performed and investigated. The method was validated using fortified bovine muscle samples. The apparent recovery (obtained after correction with an isotopically labeled I.S.) was between 89% and 97% and repeatability was less than 10%. The lowest LOD and LOQ (0.42 and 1.39μg/kg, respectively) were obtained with LC-QqQ-MS/MS.
Evaluation of a generic multi-analyte method for detection of >100 representative compounds correlated to emergency events in 19 food types by ultrahigh-pressure liquid chromatography–tandem mass spectrometry
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Anders Herrmann, Johan Rosén, Daniel Jansson, Karl-Erik Hellenäs
A generic extraction procedure combined with triple quadrupole mass spectrometric detection was evaluated for multi-residue analysis in 19 different foods. Measurable peaks could be obtained at relevant concentrations for 108 out of a total of 127 targeted compounds representing a wide range of physicochemical properties and compound classes related to emergency situations. Recoveries were determined for all 19 foods spiked with the 108 compounds. Seventy-five percent of the compounds had extraction recoveries of 70% or higher, with no compound below 46%. Suppression or enhancement effects on the MS response of the compounds dissolved in the extracts were low, as more than 80% of them had matrix effects between −35% and +20% and no compound was below −44% compared to matrix-free standard. In a validation, all compounds could be quantified at 200μg/kg and 400μg/kg food sample and 81% of the compounds at 40μg/kg. It is concluded that the method is useful for the detection of various types of organic chemical toxicants at levels generally well below concentration thresholds for severe acute intoxication.
Source:Journal of Chromatography A, Volume 1235
Anders Herrmann, Johan Rosén, Daniel Jansson, Karl-Erik Hellenäs
A generic extraction procedure combined with triple quadrupole mass spectrometric detection was evaluated for multi-residue analysis in 19 different foods. Measurable peaks could be obtained at relevant concentrations for 108 out of a total of 127 targeted compounds representing a wide range of physicochemical properties and compound classes related to emergency situations. Recoveries were determined for all 19 foods spiked with the 108 compounds. Seventy-five percent of the compounds had extraction recoveries of 70% or higher, with no compound below 46%. Suppression or enhancement effects on the MS response of the compounds dissolved in the extracts were low, as more than 80% of them had matrix effects between −35% and +20% and no compound was below −44% compared to matrix-free standard. In a validation, all compounds could be quantified at 200μg/kg and 400μg/kg food sample and 81% of the compounds at 40μg/kg. It is concluded that the method is useful for the detection of various types of organic chemical toxicants at levels generally well below concentration thresholds for severe acute intoxication.
Simultaneous determination of jasmonic acid epimers as phytohormones by chiral liquid chromatography–quadrupole time-of-flight mass spectrometry and their epimerization study
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Yehua Han, Zhigui Zhou, Hongliang Wu, Honggang Nie, Rong Lei, Yu Bai, Huwei Liu
Jasmonic acid (JA) is an essential plant hormone involved in plant development and defense system. There are four stereoisomeric forms of JA and they act quite differently in vivo. In this work, a normal phase liquid chromatography–quadrupole time-of-flight mass spectrometry (NPLC–QTOF-MS) method using cellulose tris (4-methylbenzoate) coated silica gel as the chiral stationary phase was first established for the simultaneous discrimination and direct analysis of all the four JA stereoisomers without need of derivatization. A non-endogenous JA stereoisomer was introduced as the internal standard to ensure the reliability of the developed method. Satisfactory results were obtained in terms of sensitivity (limit of detection, 0.5ngmL−1 or 2.4fmol), linearity (R 2 =0.9996) and repeatability (run-to-run RSD of migration time and peak area, 0.37% and 5.9%, respectively, n =6). Endogenous rise of two natural JA stereoisomers was detected in tobacco leaves and their variations in response to mechanical wounding were monitored. In addition, the configurational stability of JA stereoisomers was investigated using the stereoisomerically pure forms which were not commercially available but easily obtained by our semi-preparative chiral LC method. Experimental evidence indicated that both of the two naturally existing JA stereoisomers were putative signals for wounding response, and the epimerization between them was not a spontaneous process simply promoted by the thermodynamical instability as expected before.
Source:Journal of Chromatography A, Volume 1235
Yehua Han, Zhigui Zhou, Hongliang Wu, Honggang Nie, Rong Lei, Yu Bai, Huwei Liu
Jasmonic acid (JA) is an essential plant hormone involved in plant development and defense system. There are four stereoisomeric forms of JA and they act quite differently in vivo. In this work, a normal phase liquid chromatography–quadrupole time-of-flight mass spectrometry (NPLC–QTOF-MS) method using cellulose tris (4-methylbenzoate) coated silica gel as the chiral stationary phase was first established for the simultaneous discrimination and direct analysis of all the four JA stereoisomers without need of derivatization. A non-endogenous JA stereoisomer was introduced as the internal standard to ensure the reliability of the developed method. Satisfactory results were obtained in terms of sensitivity (limit of detection, 0.5ngmL−1 or 2.4fmol), linearity (R 2 =0.9996) and repeatability (run-to-run RSD of migration time and peak area, 0.37% and 5.9%, respectively, n =6). Endogenous rise of two natural JA stereoisomers was detected in tobacco leaves and their variations in response to mechanical wounding were monitored. In addition, the configurational stability of JA stereoisomers was investigated using the stereoisomerically pure forms which were not commercially available but easily obtained by our semi-preparative chiral LC method. Experimental evidence indicated that both of the two naturally existing JA stereoisomers were putative signals for wounding response, and the epimerization between them was not a spontaneous process simply promoted by the thermodynamical instability as expected before.
Derivatization and liquid chromatography–UV–tandem mass spectrometric analysis of perfluorinated carboxylic acids
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Jinxue Qiu, Chunmei Wu, Yingyu Fang, Cui Yang, Xiuhua Li, Xiangfan Piao, Donghao Li
The presence of perfluorocarboxylates (PFCAs) in the environment is of increasing concern due to their possible toxicity to humans and bioaccumulation in organisms. PFCAs are frequently found in river water, sediment and organisms and sometimes even in groundwater. In order to quantitatively determine these PFCAs, a fast derivatization coupled with a liquid chromatography–ultraviolet detector–electrospray ionization-tandem mass spectrometry (LC–UV–ESI-MS/MS) method was developed. The PFCAs were quantitatively converted to their corresponding phenacyl esters using p-bromophenacyl bromide as the derivatization reagent. Under optimized reaction conditions, the conversion yield of the PFCAs ranged from 86 to 92% with low %RSD. The typical derivatization product (p-bromophenacyl bromide perfluorooctanoate) was characterized by 1H NMR, 13C NMR, FT-IR and mass spectrometry. UPLC with a BEH C18 column and CAN/H2O (8/2, v/v) as a mobile phase were used to separate the derivatives. The analytes were completely eluted within 6min and multidimensional detection using UV at 260nm and ESI–MRM in the negative ion mode were carried out. Bromide isotopic characteristic fragment ions appeared in the first Q1 scans, and four daughter ions of the MRMs at m/z [M−H−222]−, [M−H−250]–, [M−H−278]− and [M−H−316]− were used for quantification and confirmation. The mass spectral information ensured accurate identification of the analytes even when the sample matrices were complex. The method successfully eliminated the PFCAs background problems originating from polymeric parts in liquid chromatographic systems. The LODs of the method were lower than 5ngmL−1, and the relative standard deviation (RSD%) values ranged from 5.2 to 9.8%. The method was successfully applied for the quantification of PFCAs in river water contaminated by industrial wastewater, and this indicated that the method was useful in the determination of PFCAs in environmental samples.
Source:Journal of Chromatography A, Volume 1235
Jinxue Qiu, Chunmei Wu, Yingyu Fang, Cui Yang, Xiuhua Li, Xiangfan Piao, Donghao Li
The presence of perfluorocarboxylates (PFCAs) in the environment is of increasing concern due to their possible toxicity to humans and bioaccumulation in organisms. PFCAs are frequently found in river water, sediment and organisms and sometimes even in groundwater. In order to quantitatively determine these PFCAs, a fast derivatization coupled with a liquid chromatography–ultraviolet detector–electrospray ionization-tandem mass spectrometry (LC–UV–ESI-MS/MS) method was developed. The PFCAs were quantitatively converted to their corresponding phenacyl esters using p-bromophenacyl bromide as the derivatization reagent. Under optimized reaction conditions, the conversion yield of the PFCAs ranged from 86 to 92% with low %RSD. The typical derivatization product (p-bromophenacyl bromide perfluorooctanoate) was characterized by 1H NMR, 13C NMR, FT-IR and mass spectrometry. UPLC with a BEH C18 column and CAN/H2O (8/2, v/v) as a mobile phase were used to separate the derivatives. The analytes were completely eluted within 6min and multidimensional detection using UV at 260nm and ESI–MRM in the negative ion mode were carried out. Bromide isotopic characteristic fragment ions appeared in the first Q1 scans, and four daughter ions of the MRMs at m/z [M−H−222]−, [M−H−250]–, [M−H−278]− and [M−H−316]− were used for quantification and confirmation. The mass spectral information ensured accurate identification of the analytes even when the sample matrices were complex. The method successfully eliminated the PFCAs background problems originating from polymeric parts in liquid chromatographic systems. The LODs of the method were lower than 5ngmL−1, and the relative standard deviation (RSD%) values ranged from 5.2 to 9.8%. The method was successfully applied for the quantification of PFCAs in river water contaminated by industrial wastewater, and this indicated that the method was useful in the determination of PFCAs in environmental samples.
Atmospheric pressure gas chromatography coupled to quadrupole-time of flight mass spectrometry as a powerful tool for identification of non intentionally added substances in acrylic adhesives used in food packaging materials
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
E. Canellas, P. Vera, C. Domeño, P. Alfaro, C. Nerín
Acrylic adhesives are used to manufacture multilayer laminates that are used in food packaging to form the geometric shape of the package as well as to stick labels on the packages. Once applied on the packaging adhesives can supply potential migrants that could endanger the packaged food. Adhesives are complex matrices where intentionally and non intentionally added substances are present, but the identification of the migrants is required by law. In this study atmospheric pressure gas chromatography coupled to a quadrupole hyphenated to a time of flight mass spectrometer (APGC–MS/Q-TOF) has been explored for identification of unknowns coming from three different acrylic adhesives. The results are compared to those obtained by conventional GC–MS-Q (quadrupole). Sixteen compounds were identified by GC–MS/Q and five of them were confirmed by APGC–MS/Q-TOF as their molecular ions were found. Moreover, additional three new compounds were identified and their structure was elucidated working with the spectra obtained by APGC–MS/Q-TOF. This finding was very relevant as these compounds were biocides suspected to be allergenic and cytotoxic in humans. Migration studies were carried out using Tenax as solid food simulant and the results showed that the three acrylic adhesives tested in this work were safe for being used in food packaging materials since the migration of compounds previously identified was below the limit established in the current legislation.
Source:Journal of Chromatography A, Volume 1235
E. Canellas, P. Vera, C. Domeño, P. Alfaro, C. Nerín
Acrylic adhesives are used to manufacture multilayer laminates that are used in food packaging to form the geometric shape of the package as well as to stick labels on the packages. Once applied on the packaging adhesives can supply potential migrants that could endanger the packaged food. Adhesives are complex matrices where intentionally and non intentionally added substances are present, but the identification of the migrants is required by law. In this study atmospheric pressure gas chromatography coupled to a quadrupole hyphenated to a time of flight mass spectrometer (APGC–MS/Q-TOF) has been explored for identification of unknowns coming from three different acrylic adhesives. The results are compared to those obtained by conventional GC–MS-Q (quadrupole). Sixteen compounds were identified by GC–MS/Q and five of them were confirmed by APGC–MS/Q-TOF as their molecular ions were found. Moreover, additional three new compounds were identified and their structure was elucidated working with the spectra obtained by APGC–MS/Q-TOF. This finding was very relevant as these compounds were biocides suspected to be allergenic and cytotoxic in humans. Migration studies were carried out using Tenax as solid food simulant and the results showed that the three acrylic adhesives tested in this work were safe for being used in food packaging materials since the migration of compounds previously identified was below the limit established in the current legislation.
Source identification of petroleum hydrocarbons in soil and sediments from Iguaçu River Watershed, Paraná, Brazil using the CHEMSIC method (CHEMometric analysis of Selected Ion Chromatograms)
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Fabiana D.C. Gallotta, Jan H. Christensen
A chemometric method based on principal component analysis (PCA) of pre-processed and combined sections of selected ion chromatograms (SICs) is used to characterise the hydrocarbon profiles in soil and sediment from Araucária, Guajuvira, General Lúcio and Balsa Nova Municipalities (Iguaçu River Watershed, Paraná, Brazil) and to indicate the main sources of hydrocarbon pollution. The study includes 38 SICs of polycyclic aromatic compounds (PACs) and four of petroleum biomarkers in two separate analyses. The most contaminated samples are inside the Presidente Getúlio Vargas Refinery area. These samples represent a petrogenic pattern and different weathering degrees. Samples from outside the refinery area are either less or not contaminated, or contain mixtures of diagenetic, pyrogenic and petrogenic inputs where different proportions predominate. The locations farthest away from industrial activity (Balsa Nova) contains the lowest levels of PAC contamination. There are no evidences to conclude positive matches between the samples from outside the refinery area and the Cusiana spilled oil.
Source:Journal of Chromatography A, Volume 1235
Fabiana D.C. Gallotta, Jan H. Christensen
A chemometric method based on principal component analysis (PCA) of pre-processed and combined sections of selected ion chromatograms (SICs) is used to characterise the hydrocarbon profiles in soil and sediment from Araucária, Guajuvira, General Lúcio and Balsa Nova Municipalities (Iguaçu River Watershed, Paraná, Brazil) and to indicate the main sources of hydrocarbon pollution. The study includes 38 SICs of polycyclic aromatic compounds (PACs) and four of petroleum biomarkers in two separate analyses. The most contaminated samples are inside the Presidente Getúlio Vargas Refinery area. These samples represent a petrogenic pattern and different weathering degrees. Samples from outside the refinery area are either less or not contaminated, or contain mixtures of diagenetic, pyrogenic and petrogenic inputs where different proportions predominate. The locations farthest away from industrial activity (Balsa Nova) contains the lowest levels of PAC contamination. There are no evidences to conclude positive matches between the samples from outside the refinery area and the Cusiana spilled oil.
Determination of descriptors for fragrance compounds by gas chromatography and liquid–liquid partition
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Thushara Karunasekara, Colin F. Poole
Retention factors on a minimum of eight stationary phases at various temperatures by gas–liquid chromatography and liquid–liquid partition coefficients for five totally organic biphasic systems were combined to estimate descriptors for 28 fragrance compounds with an emphasis on compounds that are known or potential allergens. The descriptors facilitated the estimation of several properties of biological and environmental interest (sensory irritation threshold, odor detection threshold, nasal pungency threshold, skin permeability from water, skin–water partition coefficients, octanol–water partition coefficients, absorption by air particles, adsorption by diesel soot particles, air–water partition coefficients, and adsorption by film water). The descriptors are suitable for use in the solvation parameter model and facilitate the estimation of a wide range of physicochemical, chromatographic, biological, and environmental properties using existing models.
Source:Journal of Chromatography A, Volume 1235
Thushara Karunasekara, Colin F. Poole
Retention factors on a minimum of eight stationary phases at various temperatures by gas–liquid chromatography and liquid–liquid partition coefficients for five totally organic biphasic systems were combined to estimate descriptors for 28 fragrance compounds with an emphasis on compounds that are known or potential allergens. The descriptors facilitated the estimation of several properties of biological and environmental interest (sensory irritation threshold, odor detection threshold, nasal pungency threshold, skin permeability from water, skin–water partition coefficients, octanol–water partition coefficients, absorption by air particles, adsorption by diesel soot particles, air–water partition coefficients, and adsorption by film water). The descriptors are suitable for use in the solvation parameter model and facilitate the estimation of a wide range of physicochemical, chromatographic, biological, and environmental properties using existing models.
Rapid analysis of organochlorine and pyrethroid pesticides in tea samples by directly suspended droplet microextraction using a gas chromatography–electron capture detector
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Dan Liu, Shungeng Min
A simple and efficient directly suspended droplet microextraction (DSDME) has been developed to extract and pre-concentrate organochlorine and pyrethrin pesticides from tea samples prior to analysis by a gas chromatography–electron capture detector (GC–ECD). The optimal experimental conditions of DSDME were: 100μL isooctane exposed for 15min to 5mL of the tea aqueous sample stirred at 1100rpm. For most of the target analytes, the optimal pretreatment of DSDME processes led to no significant interference of tea matrices. The approach was applied to the determination of organochlorine and pyrethroid pesticides in tea samples, with a linearity range of 0.0005–2μg/mL. The relative recoveries of all the pesticides ranged between 80.0% and 120.8% with relative standard deviations (RSDs) in the range of 0.8–19.9% (n =5). The limits of detections (LODs) ranged between 0.04 and 1μg/L for all the target pesticides.
Source:Journal of Chromatography A, Volume 1235
Dan Liu, Shungeng Min
A simple and efficient directly suspended droplet microextraction (DSDME) has been developed to extract and pre-concentrate organochlorine and pyrethrin pesticides from tea samples prior to analysis by a gas chromatography–electron capture detector (GC–ECD). The optimal experimental conditions of DSDME were: 100μL isooctane exposed for 15min to 5mL of the tea aqueous sample stirred at 1100rpm. For most of the target analytes, the optimal pretreatment of DSDME processes led to no significant interference of tea matrices. The approach was applied to the determination of organochlorine and pyrethroid pesticides in tea samples, with a linearity range of 0.0005–2μg/mL. The relative recoveries of all the pesticides ranged between 80.0% and 120.8% with relative standard deviations (RSDs) in the range of 0.8–19.9% (n =5). The limits of detections (LODs) ranged between 0.04 and 1μg/L for all the target pesticides.
Taylor dispersion analysis with two detection points on a commercial capillary electrophoresis apparatus
29 March 2012,
09:38:25
Publication year:
2012
Source:Journal of Chromatography A, Volume 1235
Joseph Chamieh, Farid Oukacine, Hervé Cottet
This work describes a simple technical modification for doing Taylor dispersion analysis with two UV detection points on a commercial capillary electrophoresis apparatus. So far, double UV detection was only possible using specific detectors that are external to the capillary electrophoresis apparatus. In this work, the detection interface of the capillary electrophoresis apparatus was easily modified to allow the introduction and the superposition of two capillary windows in the same interface (at the same detection point). This modification made possible the double detection of the sample zone in Taylor dispersion analysis using a loop. The peak dispersion using the modified interface was similar to that obtained on a non-modified UV interface. Diffusion coefficients (and the corresponding hydrodynamic radii) of small molecule and proteins were determined in good agreement with values of the literature and with RSD lower than 5%.
Source:Journal of Chromatography A, Volume 1235
Joseph Chamieh, Farid Oukacine, Hervé Cottet
This work describes a simple technical modification for doing Taylor dispersion analysis with two UV detection points on a commercial capillary electrophoresis apparatus. So far, double UV detection was only possible using specific detectors that are external to the capillary electrophoresis apparatus. In this work, the detection interface of the capillary electrophoresis apparatus was easily modified to allow the introduction and the superposition of two capillary windows in the same interface (at the same detection point). This modification made possible the double detection of the sample zone in Taylor dispersion analysis using a loop. The peak dispersion using the modified interface was similar to that obtained on a non-modified UV interface. Diffusion coefficients (and the corresponding hydrodynamic radii) of small molecule and proteins were determined in good agreement with values of the literature and with RSD lower than 5%.
Improving the efficiency of Collagen coating of plates and flasks
INTEGRA has released an application note that describes a new protocol using
its DOSE IT peristaltic pump that significantly improves the efficiency of
collagen coating of plates and flasks.
Coating of dishes or tissue culture flasks with extra cellular matrix proteins like Collagen or Fibronectin is a common procedure in laboratories involved in cell culture. However, coating large numbers of disposables is a tedious and time-consuming task. This application note describes how using a DOSE-IT peristaltic pump results in 40% time-savings compared to a regular pipette controller and at the same time helps to reduce excessive strain caused by this repetitive work.
An online video demonstrating the DOSE IT peristaltic pump protocol may be viewed at www.integra-biosciences.com/sites/pdf/Improving_the_efficiency_of_collagen_coating_V01.pdf. For a copy of this application note contact INTEGRA on +41-81-286-9530 / info@integra-biosciences.com (Europe / Asia Pacific) or +1-603-578-5800 / contact@viaflo.com (North / South America).
DOSE IT is an intuitive programmable peristaltic pump that simplifies the dispensing of cell culture media, buffers and other solutions for volumes ranging from 0.1mL to 2500mL. DOSE IT features a very small footprint and weighs only 3.5Kg making it a perfect device for bench-top or in-hood dispensing applications. Programming the DOSE IT is fast and easy through a multilingual user interface (English, Spanish, German, French and Italian). The instrument's pump head accommodates the use of different tubing diameters (1-8mm) allowing a wide range of volumes to be dispensed with optimal speed and precision. A built-in print capability supports the capture of program details for record keeping and quality control. Many accessories are available to support a variety of dispensing applications.
Coating of dishes or tissue culture flasks with extra cellular matrix proteins like Collagen or Fibronectin is a common procedure in laboratories involved in cell culture. However, coating large numbers of disposables is a tedious and time-consuming task. This application note describes how using a DOSE-IT peristaltic pump results in 40% time-savings compared to a regular pipette controller and at the same time helps to reduce excessive strain caused by this repetitive work.
An online video demonstrating the DOSE IT peristaltic pump protocol may be viewed at www.integra-biosciences.com/sites/pdf/Improving_the_efficiency_of_collagen_coating_V01.pdf. For a copy of this application note contact INTEGRA on +41-81-286-9530 / info@integra-biosciences.com (Europe / Asia Pacific) or +1-603-578-5800 / contact@viaflo.com (North / South America).
DOSE IT is an intuitive programmable peristaltic pump that simplifies the dispensing of cell culture media, buffers and other solutions for volumes ranging from 0.1mL to 2500mL. DOSE IT features a very small footprint and weighs only 3.5Kg making it a perfect device for bench-top or in-hood dispensing applications. Programming the DOSE IT is fast and easy through a multilingual user interface (English, Spanish, German, French and Italian). The instrument's pump head accommodates the use of different tubing diameters (1-8mm) allowing a wide range of volumes to be dispensed with optimal speed and precision. A built-in print capability supports the capture of program details for record keeping and quality control. Many accessories are available to support a variety of dispensing applications.
Oxford Instruments hosts Nanoscale Plasma Processing Seminar in Shanghai
Following the great success of
their Seminar hosted with the IOS-CAS in Beijing last year attended by over 100
participants, Oxford Instruments will hold a one day Seminar on 19th March in
Shanghai, focussing on Nanoscale Plasma Processing.
This one day event, being held
the day before Semicon China 2012, will feature talks by a number of invited
guest speakers, specialists from China, Taiwan and Europe, in addition to
Process and Applications experts from Oxford Instruments Plasma Technology.
These academic and industrial
experts will discuss topics including Atomic Layer Deposition (ALD),
Photovoltaics (PV), Deep Silicon Etch and Ion Beam technologies during the full
one day programme.
In addition to Oxford Instruments
speakers, talks from guest speakers include:
·
Introduction
to ALD and its applications, including photovoltaics; Prof Erwin Kessels,
University of Eindhoven (TU/e), Netherlands
·
Etch
& deposition process in the OPTO and MEMS application device; Dr. Chu
Ann-Kuo, Professor of Department of Photonics, National Sun Yat-sen University,
Taiwan
·
Infrared
Focal Plane Arrays (IRFPAs) detector for space applications; Dr. Zhenghua YE,
SITP (Shanghai Institute of Technology Physics)
·
Micro/Nano
fabrication and characterization of Si field electron emitters; Guest
Speaker: Dr. Juncong SHE, Sun Yat-Sen University, China
·
ALD
used in the MEMS application; Jerry Wang, Manager of Microsystems Technology
Center, ITRI, Taiwan
Jeffrey Seah, Asia Business
Manager, Oxford Instruments Plasma Technology, who will open the Seminar
comments: “We are anticipating a large audience at this Seminar in Shanghai,
and are extremely honoured that so many distinguished guest speakers have
accepted our invitation to speak about their work in Plasma Processing. Our
Seminars are a great opportunity for the Plasma Processing community to come
together, to share their experiences, and to learn more from leading
international experts in their field.”
Based on the success of the 2011
Seminar in Beijing, Oxford Instruments anticipates a very high level of
interest from both academic and production participants, attracted by such an
interesting programme and prestigious speakers.
The event is free to
attend, but booking is essential via process.news@oxinst.com
or lingling.wang@oxinst.com
Wednesday, 28 March 2012
MASTERBATCH 2012 CONFERENCE CELEBRATES 25 YEARS
The programme has been announced for the AMI Masterbatch 2012 conference, which this year will be celebrating its 25th Anniversary. The first event was held in London in 1987 and it has since become well established as the regular international forum for the global masterbatch industry attracting over 200 attendees every year.
A series of
presentations will look at the latest trends in colorants, special effect
pigments and functional additives to give fresh insight into how to add value
to products. The pigments session will include papers from Cabot,
Nubiola, BASF, MCA Technologies and Merck, while the materials session will
look at developments in resins and functional additives with papers from BASF
Schweiz, Dupont, Danisco and Sabic. The conference will also include updates
from equipment suppliers on how to improve performance and cut costs and
include presentations from major equipment suppliers including Buss, Coperion
and Leistritz. This will be complimented by presentations looking at design and
colour trends in consumer products and what that will mean for the use of
masterbatch.
Speakers
from Minima Design, Comai and Gabriel Chemie will consider these issues.
The
conference will also provide detailed analysis of the current global market
trends and AMI's Research Director, Andrew Reynolds, will be presenting the
findings of AMI's latest in-depth research into the worldwide masterbatch
market and the future development of the industry.
In addition
to delivering quality papers Masterbatch 2012 also offers superb and
cost-effective networking opportunities with its extensive table top exhibition
area.
The full
programme can now be found on AMI's website: www.amiplastics.com For further
information on attending, exhibiting or sponsoring this event please contact
Sabine Prack at AMI Conferences: sp@amiplastics.com
Avid Nano in Next Generation DLS Development Initiative
Avid Nano Limited (High Wycombe, UK), manufacturers of unique dynamic light
scattering (DLS) systems are to develop new technology for identification and
size measurement of engineered nanoparticles in the environment. The
company have joined a consortium of SMEs and the European Commission under the
European Seventh Framework Programme (FP7) in an effort to properly assess the
fate and potential safety risks associated with engineered nanoparticles (ENPs)
being increasingly deployed in such everyday things as paints, cosmetics,
sunscreens, deodorants and medicines.
The 'SMART-NANO' project partners, coordinated by Centre Suisse d'Electronique et de Microtechnique (CSEM), Switzerland and the Joint Research Center-European Commission (JRC), Italy plan to develop an innovative and cost-effective technology platform based on ready-to-use, application-specific cartridges for the detection, identification, and quantification of ENPs in complex matrices such as biological systems, consumer products, food and the environment.
Avid Nano will develop a hyper sensitive DLS system to detect and measure the size and character of ENPs in minute quantities. The company will work in close collaboration with Professor Robert Brown of the Advanced Technology Center at Rockwell Collins and the University of California, a world renowned expert in the field of optoelectronics and optics.
The founder of Avid Nano, Ken Cunningham said "We are delighted to be joining the SMART-NANO project and it is testament to the impact our young company has made on the industry that we have been selected as partners in this exciting initiative".
Operating from its UK headquarters - Avid Nano is building a strong reputation for its technical expertise, applications support and delivering DLS systems that reliably deliver top quality results. For further information please contact Avid Nano via its website or telephone +44-1494-614659 / email info@avidnano.com.
The 'SMART-NANO' project partners, coordinated by Centre Suisse d'Electronique et de Microtechnique (CSEM), Switzerland and the Joint Research Center-European Commission (JRC), Italy plan to develop an innovative and cost-effective technology platform based on ready-to-use, application-specific cartridges for the detection, identification, and quantification of ENPs in complex matrices such as biological systems, consumer products, food and the environment.
Avid Nano will develop a hyper sensitive DLS system to detect and measure the size and character of ENPs in minute quantities. The company will work in close collaboration with Professor Robert Brown of the Advanced Technology Center at Rockwell Collins and the University of California, a world renowned expert in the field of optoelectronics and optics.
The founder of Avid Nano, Ken Cunningham said "We are delighted to be joining the SMART-NANO project and it is testament to the impact our young company has made on the industry that we have been selected as partners in this exciting initiative".
Operating from its UK headquarters - Avid Nano is building a strong reputation for its technical expertise, applications support and delivering DLS systems that reliably deliver top quality results. For further information please contact Avid Nano via its website or telephone +44-1494-614659 / email info@avidnano.com.
Tuesday, 27 March 2012
Just Published: Journal of Chromatography A
A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Selected
papers from the latest issue:
On-line coupling of a clean-up device with supported liquid membrane to capillary electrophoresis for direct injection and analysis of serum and plasma samples
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Pavel Kubáň, Petr Boček
A simple sample clean-up device with planar supported liquid membrane (SLM) was developed and coupled on-line to capillary electrophoresis (CE) for direct injection of human body fluids. Donor and acceptor compartments of the device were filled with diluted body fluid and deionized water, respectively, and the two solutions were separated by a thin SLM. Analytes of interest were selectively transported from the donor solution through the SLM into the acceptor solution by diffusion whereas interfering matrix components were efficiently retained on the SLM. Equilibrium between the concentrations of analytes at the SLM was obtained typically in 5min. Then a CE separation capillary was inserted into the acceptor compartment to firmly touch the SLM and the pretreated sample was hydrodynamically injected into the capillary. The analytical procedure was demonstrated by rapid pretreatment, on-line injection, and CE determination of selected amino acids in human serum and plasma samples. 1-Ethyl-2-nitrobenezene and bis(2-ethylhexyl) phosphate (15%, v/v) was used as the selective SLM for clean-up of the body fluids and 0.5M acetic acid was used as a background electrolyte solution for CE analysis of the pretreated amino acids. Concentrations of amino acids on acceptor side of the SLM reached 40–58% of their original concentrations in donor solution after 5min equilibration time and then remained constant proving that equilibrium was achieved at the SLM. Injection of the pretreated samples was highly repeatable with RSD values of peak areas 2.4–8.4% and 3.4–10.5% for standard solutions and real samples, respectively. Limits of detection between 0.75 and 2.5μM were achieved, corresponding to 3.75–12.5μM in 1:4 diluted real samples, which ensure sensitive determination of most amino acids in the body fluids. The developed method is fast, simple, efficient, cheap and selective and may be applied to determination of a wide range of analytes in various samples with complex matrices.
Source:Journal of Chromatography A, Volume 1234
Pavel Kubáň, Petr Boček
A simple sample clean-up device with planar supported liquid membrane (SLM) was developed and coupled on-line to capillary electrophoresis (CE) for direct injection of human body fluids. Donor and acceptor compartments of the device were filled with diluted body fluid and deionized water, respectively, and the two solutions were separated by a thin SLM. Analytes of interest were selectively transported from the donor solution through the SLM into the acceptor solution by diffusion whereas interfering matrix components were efficiently retained on the SLM. Equilibrium between the concentrations of analytes at the SLM was obtained typically in 5min. Then a CE separation capillary was inserted into the acceptor compartment to firmly touch the SLM and the pretreated sample was hydrodynamically injected into the capillary. The analytical procedure was demonstrated by rapid pretreatment, on-line injection, and CE determination of selected amino acids in human serum and plasma samples. 1-Ethyl-2-nitrobenezene and bis(2-ethylhexyl) phosphate (15%, v/v) was used as the selective SLM for clean-up of the body fluids and 0.5M acetic acid was used as a background electrolyte solution for CE analysis of the pretreated amino acids. Concentrations of amino acids on acceptor side of the SLM reached 40–58% of their original concentrations in donor solution after 5min equilibration time and then remained constant proving that equilibrium was achieved at the SLM. Injection of the pretreated samples was highly repeatable with RSD values of peak areas 2.4–8.4% and 3.4–10.5% for standard solutions and real samples, respectively. Limits of detection between 0.75 and 2.5μM were achieved, corresponding to 3.75–12.5μM in 1:4 diluted real samples, which ensure sensitive determination of most amino acids in the body fluids. The developed method is fast, simple, efficient, cheap and selective and may be applied to determination of a wide range of analytes in various samples with complex matrices.
Electrowetting-on-dielectric actuation of droplets with capillary electrophoretic zones for off-line mass spectrometric analysis
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Jelena Gorbatsova, Maria Borissova, Mihkel Kaljurand
Present article describes a novel technique based on digital microfluidics that allows collecting fractions of interest after electrophoretic separation and detection for further ESI-MS investigation. In this technique, a mixture is injected into a capillary electrophoresis (CE) apparatus, and microliter droplets are generated at the CE outlet at a frequency high enough to fraction each compound into several droplets, compartmentalizing the CE zones into a sequence of droplets. The droplets are transported from the CE outlet to a storage tube inlet using electrowetting-on-dielectric (EWOD) for droplet actuation. By applying a vacuum at the other end of the storage tube, the droplets form a sequence of plugs separated by air gaps. The plugs stored in the tubing are later analyzed using a standalone spectrometric device. Off-line electrospray ionization mass spectrometry (ESI-MS) was used to characterize the corresponding vitamin and was performed by pumping the segmented plugs directly into a spray emitter tip. The technique could be of interest to laboratories without access to well-equipped facilities (e.g. clean-rooms or lab robots).
Source:Journal of Chromatography A, Volume 1234
Jelena Gorbatsova, Maria Borissova, Mihkel Kaljurand
Present article describes a novel technique based on digital microfluidics that allows collecting fractions of interest after electrophoretic separation and detection for further ESI-MS investigation. In this technique, a mixture is injected into a capillary electrophoresis (CE) apparatus, and microliter droplets are generated at the CE outlet at a frequency high enough to fraction each compound into several droplets, compartmentalizing the CE zones into a sequence of droplets. The droplets are transported from the CE outlet to a storage tube inlet using electrowetting-on-dielectric (EWOD) for droplet actuation. By applying a vacuum at the other end of the storage tube, the droplets form a sequence of plugs separated by air gaps. The plugs stored in the tubing are later analyzed using a standalone spectrometric device. Off-line electrospray ionization mass spectrometry (ESI-MS) was used to characterize the corresponding vitamin and was performed by pumping the segmented plugs directly into a spray emitter tip. The technique could be of interest to laboratories without access to well-equipped facilities (e.g. clean-rooms or lab robots).
Characterization of carboxylate-terminated carbosilane dendrimers and their evaluation as nanoadditives in capillary electrophoresis for vegetable protein profiling
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
C. Montealegre, B. Rasines, R. Gómez, F.J. de la Mata, C. García-Ruiz, M.L. Marina
Protein profiles are becoming an important tool to differentiate and classify varieties of several cultivars and to obtain a specific fingerprint for them. The use of protein profiles for these purposes needs to achieve high separation efficiencies to obtain a high number of well resolved peaks. In this work, carbosilane dendrimers with interior carbon–silicon bonds and negatively charged in the dendrimer surface with carboxylic acid as functional groups were employed as nanoadditives to separate soybean and olive seeds proteins. First, these dendrimers were characterized using CE to evaluate their possible impurities. A potentiometric titration was later carried out to determine their pK a values. Afterwards, the characterized dendrimers were used to improve the protein profiles obtained by EKC for vegetable proteins. Different dendrimer generations (G1, G2, and G3) and concentrations (0.01–1% m/v) were tested. The highest dendrimer generation G3 at 0.1% (m/v) allowed observing the best protein profiles for soybean and olive seeds. These results demonstrate that carboxylate-terminated carbosilane dendrimers are attractive nanoadditives in EKC for the effective separation of vegetable proteins.
Source:Journal of Chromatography A, Volume 1234
C. Montealegre, B. Rasines, R. Gómez, F.J. de la Mata, C. García-Ruiz, M.L. Marina
Protein profiles are becoming an important tool to differentiate and classify varieties of several cultivars and to obtain a specific fingerprint for them. The use of protein profiles for these purposes needs to achieve high separation efficiencies to obtain a high number of well resolved peaks. In this work, carbosilane dendrimers with interior carbon–silicon bonds and negatively charged in the dendrimer surface with carboxylic acid as functional groups were employed as nanoadditives to separate soybean and olive seeds proteins. First, these dendrimers were characterized using CE to evaluate their possible impurities. A potentiometric titration was later carried out to determine their pK a values. Afterwards, the characterized dendrimers were used to improve the protein profiles obtained by EKC for vegetable proteins. Different dendrimer generations (G1, G2, and G3) and concentrations (0.01–1% m/v) were tested. The highest dendrimer generation G3 at 0.1% (m/v) allowed observing the best protein profiles for soybean and olive seeds. These results demonstrate that carboxylate-terminated carbosilane dendrimers are attractive nanoadditives in EKC for the effective separation of vegetable proteins.
Evaluation of new cellulose-based chiral stationary phases Sepapak-2 and Sepapak-4 for the enantiomeric separation of pesticides by nano liquid chromatography and capillary electrochromatography
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Virginia Pérez-Fernández, Elena Dominguez-Vega, Bezhan Chankvetadze, Antonio L. Crego, Maria Ángeles García, Maria Luisa Marina
Two novel polysaccharide-based chiral stationary phases (CSPs), known as Sepapak-2 (cellulose tris(3-chloro-4-methylphenylcarbamate)) and Sepapak-4 (cellulose tris(4-chloro-3-methylphenylcarbamate)), have been evaluated in this work for the chiral separation of a group of 16 pesticides including herbicides, insecticides and fungicides. The optimization of the mobile phase employed in nano-liquid chromatography (nano-LC) enabled the chiral separation of seven pesticides on Sepapak-2 and of nine pesticides on Sepapak-4. Due to the fact that Sepapak-4 gave better results, this column was selected to compare nano-LC and capillary electrochromatography (CEC) under the same conditions that consisted in the use of a 90/9/1 (v/v/v) ACN/H2O/ammonium formate (pH 2.5) background electrolyte (BGE). As expected, both the efficiency and the chiral resolution obtained in CEC experiments were higher than in nano-LC for all the analyzed compounds. The analytical characteristics of the CEC developed methodology were evaluated in terms of linearity, LODs, LOQs, precision, selectivity, and accuracy allowing its application to the quantitation of metalaxyl and its enantiomeric impurity in a commercial fungicide product marketed as enantiomerically pure (metalaxyl-M) and in soil and tap water samples after solid phase extraction (SPE). The determined amount of metalaxyl-M was found to be a 26% above the labeled content and it contained an enantiomeric impurity of a 3.7% of S-metalaxyl was determined.
Source:Journal of Chromatography A, Volume 1234
Virginia Pérez-Fernández, Elena Dominguez-Vega, Bezhan Chankvetadze, Antonio L. Crego, Maria Ángeles García, Maria Luisa Marina
Two novel polysaccharide-based chiral stationary phases (CSPs), known as Sepapak-2 (cellulose tris(3-chloro-4-methylphenylcarbamate)) and Sepapak-4 (cellulose tris(4-chloro-3-methylphenylcarbamate)), have been evaluated in this work for the chiral separation of a group of 16 pesticides including herbicides, insecticides and fungicides. The optimization of the mobile phase employed in nano-liquid chromatography (nano-LC) enabled the chiral separation of seven pesticides on Sepapak-2 and of nine pesticides on Sepapak-4. Due to the fact that Sepapak-4 gave better results, this column was selected to compare nano-LC and capillary electrochromatography (CEC) under the same conditions that consisted in the use of a 90/9/1 (v/v/v) ACN/H2O/ammonium formate (pH 2.5) background electrolyte (BGE). As expected, both the efficiency and the chiral resolution obtained in CEC experiments were higher than in nano-LC for all the analyzed compounds. The analytical characteristics of the CEC developed methodology were evaluated in terms of linearity, LODs, LOQs, precision, selectivity, and accuracy allowing its application to the quantitation of metalaxyl and its enantiomeric impurity in a commercial fungicide product marketed as enantiomerically pure (metalaxyl-M) and in soil and tap water samples after solid phase extraction (SPE). The determined amount of metalaxyl-M was found to be a 26% above the labeled content and it contained an enantiomeric impurity of a 3.7% of S-metalaxyl was determined.
Electromembrane extraction using stabilized constant d.c. electric current—A simple tool for improvement of extraction performance
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Andrea Šlampová, Pavel Kubáň, Petr Boček
This contribution presents an experimental approach for improvement of analytical performance of electromembrane extraction (EME), which is based on the use of stabilized constant d.c. electric current. Extractions were performed using a high voltage power supply, which provided stabilized constant d.c. current down to 1μA and facilitated current-controlled transfer of ions of interest from a donor solution through a supported liquid membrane (SLM) into an acceptor solution. Repeatability of the extraction process has significantly improved for EME at constant electric current compared to EME at constant voltage. The improved repeatability of the extraction process was demonstrated on EME-capillary electrophoresis (EME-CE) analyses of selected basic drugs and amino acids in standard solutions and in human urine and serum samples. RSD values of peak areas of the analytes for EME-CE analyses were about two-fold better for EME at constant electric current (2.8–8.9%) compared to EME at constant voltage (3.6–17.8%). Other analytical parameters of the EME-CE methods, such as limits of detection, linear ranges and correlation coefficients were not statistically different for the two EME modes. Moreover, EME at constant electric current did not suffer from SLM instabilities frequently observed for EME at constant voltage.
Source:Journal of Chromatography A, Volume 1234
Andrea Šlampová, Pavel Kubáň, Petr Boček
This contribution presents an experimental approach for improvement of analytical performance of electromembrane extraction (EME), which is based on the use of stabilized constant d.c. electric current. Extractions were performed using a high voltage power supply, which provided stabilized constant d.c. current down to 1μA and facilitated current-controlled transfer of ions of interest from a donor solution through a supported liquid membrane (SLM) into an acceptor solution. Repeatability of the extraction process has significantly improved for EME at constant electric current compared to EME at constant voltage. The improved repeatability of the extraction process was demonstrated on EME-capillary electrophoresis (EME-CE) analyses of selected basic drugs and amino acids in standard solutions and in human urine and serum samples. RSD values of peak areas of the analytes for EME-CE analyses were about two-fold better for EME at constant electric current (2.8–8.9%) compared to EME at constant voltage (3.6–17.8%). Other analytical parameters of the EME-CE methods, such as limits of detection, linear ranges and correlation coefficients were not statistically different for the two EME modes. Moreover, EME at constant electric current did not suffer from SLM instabilities frequently observed for EME at constant voltage.
Analysis of polyphenols and methylxantines in tea samples by means of nano-liquid chromatography utilizing capillary columns packed with core–shell particles
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Chiara Fanali, Anna Rocco, Zeineb Aturki, Luigi Mondello, Salvatore Fanali
In this study, a rapid separation of eleven polyphenols and three methylxanthines was obtained by means of nano-liquid chromatography (nano-LC), employing a 100μm I.D. capillary column packed with C18 core–shell particles (2.7μm) for 10cm. All compounds were baseline resolved with a step gradient elution in less than 15min. The developed analytical method was validated and the resulting RSD% for intra-day and inter-day repeatability, related to retention time, retention factor and peak area, were below 5.1 and 5.7%. LOD and LOQ values corresponded to 0.300 and 0.625μg/mL, while linearity range assessed gave R 2 no lower than 0.990. Then, the method was used to determine studied compounds in tea extracts. Further, the nano-LC system was coupled with a mass spectrometer to confirm the components present in real samples. Finally the results were compared with those obtained using a capillary column (100μm I.D.×10cm) packed with C18 sub-2μm particles, applying the same nano-LC experimental conditions.
Source:Journal of Chromatography A, Volume 1234
Chiara Fanali, Anna Rocco, Zeineb Aturki, Luigi Mondello, Salvatore Fanali
In this study, a rapid separation of eleven polyphenols and three methylxanthines was obtained by means of nano-liquid chromatography (nano-LC), employing a 100μm I.D. capillary column packed with C18 core–shell particles (2.7μm) for 10cm. All compounds were baseline resolved with a step gradient elution in less than 15min. The developed analytical method was validated and the resulting RSD% for intra-day and inter-day repeatability, related to retention time, retention factor and peak area, were below 5.1 and 5.7%. LOD and LOQ values corresponded to 0.300 and 0.625μg/mL, while linearity range assessed gave R 2 no lower than 0.990. Then, the method was used to determine studied compounds in tea extracts. Further, the nano-LC system was coupled with a mass spectrometer to confirm the components present in real samples. Finally the results were compared with those obtained using a capillary column (100μm I.D.×10cm) packed with C18 sub-2μm particles, applying the same nano-LC experimental conditions.
Chiral capillary liquid chromatography based on penicillin G acylase immobilized on monolithic epoxy silica column
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Roberto Gotti, Jessica Fiori, Enrica Calleri, Caterina Temporini, Dieter Lubda, Gabriella Massolini
An epoxy derivatized monolithic silica capillary column (100μm i.d.) was used as a support for immobilization of penicillin G acylase (PGA), an enzyme used in the production of semisynthetic antibiotics. In order to allow for sensitive UV detection, the PGA-based monolithic capillary column was coupled to an open fused-silica capillary via a TFE (Teflon®) shrink tube sleeve (1cm long, 300μm i.d.), which proved to be a robust, dead-volume free and easily replaceable connector. This configuration resulted in a duplex fritless column for capillary liquid chromatography (CLC) and electrically assisted CLC (eCLC). In particular, using the driving pressure (2–12bar) supplied by the commercial CE instruments, CLC separations could be obtained in short time due to the low column backpressure of the monolith. In particular, the developed stationary phase characterized by the chiral recognition ability of PGA, was successfully applied in enantioseparation of arylpropionic acids of pharmaceutical interest (i.e., profens). As an example, by using a 7cm long monolith capillary column, the enantioresolution (Rs>3.0) of rac-ketoprofen was achieved in less than 2min (pressure 12bar) with a minimum plate height in the order of 20μm and using as a mobile phase a 50mM phosphate buffer pH 7.0. Validation data such as repeatability of retention time (intraday<0.62, n =6; interday<1.62, n =9; and column-to-column<10.5, n =2), linearity (r 2 =0.999), and sensitivity (LOQ 0.25% (w/w) of (R)-ketoprofen with respect to (S)-ketoprofen) showed good method performance. The method was successfully applied to the determination of (S)-ketoprofen in pharmaceutical samples (tablets).
Source:Journal of Chromatography A, Volume 1234
Roberto Gotti, Jessica Fiori, Enrica Calleri, Caterina Temporini, Dieter Lubda, Gabriella Massolini
An epoxy derivatized monolithic silica capillary column (100μm i.d.) was used as a support for immobilization of penicillin G acylase (PGA), an enzyme used in the production of semisynthetic antibiotics. In order to allow for sensitive UV detection, the PGA-based monolithic capillary column was coupled to an open fused-silica capillary via a TFE (Teflon®) shrink tube sleeve (1cm long, 300μm i.d.), which proved to be a robust, dead-volume free and easily replaceable connector. This configuration resulted in a duplex fritless column for capillary liquid chromatography (CLC) and electrically assisted CLC (eCLC). In particular, using the driving pressure (2–12bar) supplied by the commercial CE instruments, CLC separations could be obtained in short time due to the low column backpressure of the monolith. In particular, the developed stationary phase characterized by the chiral recognition ability of PGA, was successfully applied in enantioseparation of arylpropionic acids of pharmaceutical interest (i.e., profens). As an example, by using a 7cm long monolith capillary column, the enantioresolution (Rs>3.0) of rac-ketoprofen was achieved in less than 2min (pressure 12bar) with a minimum plate height in the order of 20μm and using as a mobile phase a 50mM phosphate buffer pH 7.0. Validation data such as repeatability of retention time (intraday<0.62, n =6; interday<1.62, n =9; and column-to-column<10.5, n =2), linearity (r 2 =0.999), and sensitivity (LOQ 0.25% (w/w) of (R)-ketoprofen with respect to (S)-ketoprofen) showed good method performance. The method was successfully applied to the determination of (S)-ketoprofen in pharmaceutical samples (tablets).
Comparative high-performance liquid chromatography enantioseparations on polysaccharide based chiral stationary phases prepared by coating totally porous and core–shell silica particles
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Ketevan Lomsadze, George Jibuti, Tivadar Farkas, Bezhan Chankvetadze
This article reports comparative high-performance liquid chromatographic separations of enantiomers with chiral stationary phases (CSPs) prepared by coating cellulose tris(4-chloro-3-methylphenylcarbamate) on totally porous and on core–shell type silica of comparable particle diameter. Several interesting observations were made: (1) the selectivity of separation was higher on core–shell type CSP compared to totally porous CSP at comparable content of chiral selector (polysaccharide derivative); (2) much flatter dependence of plate height on the mobile phase flow rate was observed for columns packet with CSP prepared with core–shell silica compared to the ones packed with CSPs prepared with totally porous particles; (3) at low mobile phase flow rates core–shell CSP provided lower resolving ability compared to a commercially available CSP having four times higher content of chiral selector along with higher retention of chiral analytes. However, at high flow rates core–shell type CSP performed similarly or better than the commercial column in regards of plate count (N) and peak resolution (R s) per column length and within a given total analysis time. The advantage of CSP prepared with core–shell silica is obvious from the viewpoint of plate numbers and resolution calculated per unit time (i.e. speed of analysis).
Source:Journal of Chromatography A, Volume 1234
Ketevan Lomsadze, George Jibuti, Tivadar Farkas, Bezhan Chankvetadze
This article reports comparative high-performance liquid chromatographic separations of enantiomers with chiral stationary phases (CSPs) prepared by coating cellulose tris(4-chloro-3-methylphenylcarbamate) on totally porous and on core–shell type silica of comparable particle diameter. Several interesting observations were made: (1) the selectivity of separation was higher on core–shell type CSP compared to totally porous CSP at comparable content of chiral selector (polysaccharide derivative); (2) much flatter dependence of plate height on the mobile phase flow rate was observed for columns packet with CSP prepared with core–shell silica compared to the ones packed with CSPs prepared with totally porous particles; (3) at low mobile phase flow rates core–shell CSP provided lower resolving ability compared to a commercially available CSP having four times higher content of chiral selector along with higher retention of chiral analytes. However, at high flow rates core–shell type CSP performed similarly or better than the commercial column in regards of plate count (N) and peak resolution (R s) per column length and within a given total analysis time. The advantage of CSP prepared with core–shell silica is obvious from the viewpoint of plate numbers and resolution calculated per unit time (i.e. speed of analysis).
Optimization of the liquid chromatography enantioseparation of chiral acidic compounds using cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector and polar organic mobile phases
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
K.S.S. Dossou, E. Farcas, A.-C. Servais, P. Chiap, B. Chankvetadze, J. Crommen, M. Fillet
The LC enantioseparation of chiral acidic and zwitterionic drugs selected as model compounds was optimized using chlorine containing cellulose based chiral stationary phases and polar organic mobile phases. The main solvent of the mobile phase was acetonitrile, the temperature was settled at 25°C and a stationary phase with cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector (3-Cl-4-Me-PC) was selected. In the screening step, the nature and concentration of both acidic and basic additives were found to have a significant effect on retention, selectivity and resolution. Acetic acid (AcA) was selected as acidic additive for the optimization step since it could lead to the enantioseparation of more acidic compounds than trifluoroacetic acid (TFA) and formic acid (FA), while among the three basic additives tested, diethylamine (DEA) most often gave better results with respect to enantioresolution and selectivity than butylamine (BuA) and triethylamine (TEA). The optimization was performed using a central composite face-centered design with two factors, namely the concentration of acetic acid (0.1–0.3%) and the concentration of DEA (0.01–0.1%) in the mobile phase. On the basis of the results obtained in the screening and optimization steps, a strategy for the rapid development of methods for the enantioseparation of acidic or neutral compounds was proposed.
Source:Journal of Chromatography A, Volume 1234
K.S.S. Dossou, E. Farcas, A.-C. Servais, P. Chiap, B. Chankvetadze, J. Crommen, M. Fillet
The LC enantioseparation of chiral acidic and zwitterionic drugs selected as model compounds was optimized using chlorine containing cellulose based chiral stationary phases and polar organic mobile phases. The main solvent of the mobile phase was acetonitrile, the temperature was settled at 25°C and a stationary phase with cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector (3-Cl-4-Me-PC) was selected. In the screening step, the nature and concentration of both acidic and basic additives were found to have a significant effect on retention, selectivity and resolution. Acetic acid (AcA) was selected as acidic additive for the optimization step since it could lead to the enantioseparation of more acidic compounds than trifluoroacetic acid (TFA) and formic acid (FA), while among the three basic additives tested, diethylamine (DEA) most often gave better results with respect to enantioresolution and selectivity than butylamine (BuA) and triethylamine (TEA). The optimization was performed using a central composite face-centered design with two factors, namely the concentration of acetic acid (0.1–0.3%) and the concentration of DEA (0.01–0.1%) in the mobile phase. On the basis of the results obtained in the screening and optimization steps, a strategy for the rapid development of methods for the enantioseparation of acidic or neutral compounds was proposed.
Development of a reversed-phase high-performance liquid chromatography analytical methodology for the determination of antihypertensive peptides in maize crops
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Patrycja Puchalska, M. Luisa Marina, M. Concepción García
The aim of this work was to estimate the content of three highly antihypertensive peptides (LQP, LSP, and LRP) in different maize crops. For that purpose, a method consisting of the extraction of the protein containing these peptides (α-zeins), releasing of peptides by thermolysin digestion, and separation and detection of peptides was designed. The rapid and efficient ultrasound assisted extraction of α-zeins proteins from whole maize kernels was achieved using 70% of ethanol followed by precipitation with acetone. A 10mM Tris–HCl (pH 8.0) buffer containing 8M urea enabled to dissolve the precipitated α-zeins. This buffer was diluted to reach a 6M urea concentration before digestion to keep active the enzyme. Other digestion parameters that were optimized were: enzyme to substrate ratio (5:100 was selected), digestion temperature (50°C) and digestion time (6h). The RP-HPLC separation in a fused-core column was also optimized allowing the separation of the three peptides extracted from maize kernels in 6min. The presence of the three antihypertensive peptides in the digested extract was confirmed using HPLC–Q-TOF-MS analysis and by comparison with peptide standards. Clear differences were observed in the content of the three antihypertensive peptides and, thus, in the antihypertensive activity of the analyzed crops. The content of LRP peptide was very low regardless of the maize variety while the content of LQP and LSP significantly varied among studied maize lines.
Source:Journal of Chromatography A, Volume 1234
Patrycja Puchalska, M. Luisa Marina, M. Concepción García
The aim of this work was to estimate the content of three highly antihypertensive peptides (LQP, LSP, and LRP) in different maize crops. For that purpose, a method consisting of the extraction of the protein containing these peptides (α-zeins), releasing of peptides by thermolysin digestion, and separation and detection of peptides was designed. The rapid and efficient ultrasound assisted extraction of α-zeins proteins from whole maize kernels was achieved using 70% of ethanol followed by precipitation with acetone. A 10mM Tris–HCl (pH 8.0) buffer containing 8M urea enabled to dissolve the precipitated α-zeins. This buffer was diluted to reach a 6M urea concentration before digestion to keep active the enzyme. Other digestion parameters that were optimized were: enzyme to substrate ratio (5:100 was selected), digestion temperature (50°C) and digestion time (6h). The RP-HPLC separation in a fused-core column was also optimized allowing the separation of the three peptides extracted from maize kernels in 6min. The presence of the three antihypertensive peptides in the digested extract was confirmed using HPLC–Q-TOF-MS analysis and by comparison with peptide standards. Clear differences were observed in the content of the three antihypertensive peptides and, thus, in the antihypertensive activity of the analyzed crops. The content of LRP peptide was very low regardless of the maize variety while the content of LQP and LSP significantly varied among studied maize lines.
Combined use of isopropylamine and trifluoroacetic acid in methanol-containing mobile phases for chiral supercritical fluid chromatography
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1234
Katrijn De Klerck, Debby Mangelings, David Clicq, Filip De Boever, Yvan Vander Heyden
In chiral supercritical fluid chromatography (SFC), mobile-phase additives are often used to improve enantioseparations and peak shapes. An acidic or basic additive is chosen, depending on the nature of the compound. This work highlights the simultaneous use of the acidic additive trifluoroacetic acid (TFA) and the basic additive isopropylamine (IPA) in supercritical fluid chromatography for enantioseparations. To evaluate the combination of TFA and IPA, 59 chiral pharmaceutical compounds were analyzed on four polysaccharide-based chiral stationary phases (CSPs): Lux® Cellulose-1, Lux® Cellulose-2, Lux® Cellulose-4 and Lux® Amylose-2. The results show that an important increase in enantioselectivity of the chromatographic system can occur when combining trifluoroacetic acid and isopropylamine in the mobile phase (MP), compared to the individual use of these additives. However, the combination of isopropylamine and trifluoroacetic acid in a supercritical methanol-containing mobile phase can also lead to problems as a result of the formation of salt complexes between the two additives. Combining the additives trifluoroacetic acid and isopropylamine and taking the appropriate measures to avoid salt formation, i.e. reducing the additives’ concentrations, can lead to simpler chiral SFC screening conditions that display even broader enantioselectivity.
Source:Journal of Chromatography A, Volume 1234
Katrijn De Klerck, Debby Mangelings, David Clicq, Filip De Boever, Yvan Vander Heyden
In chiral supercritical fluid chromatography (SFC), mobile-phase additives are often used to improve enantioseparations and peak shapes. An acidic or basic additive is chosen, depending on the nature of the compound. This work highlights the simultaneous use of the acidic additive trifluoroacetic acid (TFA) and the basic additive isopropylamine (IPA) in supercritical fluid chromatography for enantioseparations. To evaluate the combination of TFA and IPA, 59 chiral pharmaceutical compounds were analyzed on four polysaccharide-based chiral stationary phases (CSPs): Lux® Cellulose-1, Lux® Cellulose-2, Lux® Cellulose-4 and Lux® Amylose-2. The results show that an important increase in enantioselectivity of the chromatographic system can occur when combining trifluoroacetic acid and isopropylamine in the mobile phase (MP), compared to the individual use of these additives. However, the combination of isopropylamine and trifluoroacetic acid in a supercritical methanol-containing mobile phase can also lead to problems as a result of the formation of salt complexes between the two additives. Combining the additives trifluoroacetic acid and isopropylamine and taking the appropriate measures to avoid salt formation, i.e. reducing the additives’ concentrations, can lead to simpler chiral SFC screening conditions that display even broader enantioselectivity.
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Wei Liu, Lan Zhang, Liangbiao Fan, Zian Lin, Yimin Cai, Zhenyi Wei, Guonan Chen
In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent “bar” not floating at the sample solution and exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15μL toluene, 40°C, stirring at 750rpm for 30min with 1.5g sodium chloride addition in 20.0mL donor phase), the linear ranges of anabolic steroids were 0.25–200ngmL−1 with gas chromatography–mass spectrometry. The limits of detection were lower than 0.10ngmL−1. The recoveries and precisions in spiked urine and hair samples were between 73.97–93.56% and 2.18–4.47% (n =5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method.
Source:Journal of Chromatography A, Volume 1233
Wei Liu, Lan Zhang, Liangbiao Fan, Zian Lin, Yimin Cai, Zhenyi Wei, Guonan Chen
In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent “bar” not floating at the sample solution and exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15μL toluene, 40°C, stirring at 750rpm for 30min with 1.5g sodium chloride addition in 20.0mL donor phase), the linear ranges of anabolic steroids were 0.25–200ngmL−1 with gas chromatography–mass spectrometry. The limits of detection were lower than 0.10ngmL−1. The recoveries and precisions in spiked urine and hair samples were between 73.97–93.56% and 2.18–4.47% (n =5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method.
Comparative evaluation of post-column free radical scavenging and ferric reducing antioxidant power assays for screening of antioxidants in strawberries
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Raimondas Raudonis, Lina Raudone, Valdas Jakstas, Valdimaras Janulis
ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP – is based on the reduction of Fe(III)–tripyridyltriazine complex to Fe(II)–tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The research results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.
Source:Journal of Chromatography A, Volume 1233
Raimondas Raudonis, Lina Raudone, Valdas Jakstas, Valdimaras Janulis
ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP – is based on the reduction of Fe(III)–tripyridyltriazine complex to Fe(II)–tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The research results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.
Evaluation of sulfonated graphene sheets as sorbent for micro-solid-phase extraction combined with gas chromatography–mass spectrometry
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Hong Zhang, Wei Ping Low, Hian Kee Lee
This report describes the use of sulfonated graphene sheets as sorbent in micro-solid-phase extraction (μ-SPE), together with gas chromatography–mass spectrometry, for the determination of polycyclic aromatic hydrocarbons (PAHs) in water. In this study, for the first time, graphene sheets were used as a sorbent material for this mode of microextraction. The modified graphene sheets were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. μ-SPE parameters such as extraction time, desorption time and desorption solvent were optimized. The method showed good precision, reproducibility and linear response for PAH analysis over a concentration range of 0.05–100μg/L for naphthalene and 0.01–100μg/L for the remaining PAHs (acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) with coefficient of determination (r 2) of higher than 0.992. Limits of detection of from 0.8 to 3.9ng/L for 7 PAHs were achieved. The developed method was successfully applied to determine PAHs in river water samples.
Source:Journal of Chromatography A, Volume 1233
Hong Zhang, Wei Ping Low, Hian Kee Lee
This report describes the use of sulfonated graphene sheets as sorbent in micro-solid-phase extraction (μ-SPE), together with gas chromatography–mass spectrometry, for the determination of polycyclic aromatic hydrocarbons (PAHs) in water. In this study, for the first time, graphene sheets were used as a sorbent material for this mode of microextraction. The modified graphene sheets were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and elemental analysis. μ-SPE parameters such as extraction time, desorption time and desorption solvent were optimized. The method showed good precision, reproducibility and linear response for PAH analysis over a concentration range of 0.05–100μg/L for naphthalene and 0.01–100μg/L for the remaining PAHs (acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene) with coefficient of determination (r 2) of higher than 0.992. Limits of detection of from 0.8 to 3.9ng/L for 7 PAHs were achieved. The developed method was successfully applied to determine PAHs in river water samples.
Simultaneous determination of polycyclic aromatic hydrocarbons and benzene, toluene, ethylbenzene and xylene in water samples using a new sampling strategy combining different extraction modes and temperatures in a single extraction solid-phase microextraction-gas chromatography–mass spectrometry procedure
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Joyce Nunes Bianchin, Giuliana Nardini, Josias Merib, Adriana Neves Dias, Edmar Martendal, Eduardo Carasek
This study proposes a new optimization approach for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene isomers (BTEX) from water samples using the solid-phase microextraction technique followed by gas chromatography–mass spectrometry (GC–MS) separation and detection. The objective of the study was to achieve compromise extraction conditions, suitable for all semi-volatile and volatile compounds, under which the amount extracted is maximized for all analytes. This was achieved by careful optimization of the fiber coating, salting-out effect, extraction time and temperature and extraction mode (headspace or direct immersion). With the optimized fiber coating – PDMS/DVB 65μm – the other selected factors were optimized using a response surface methodology through central composite designs. As expected, the optimized results for each class of analytes varied significantly, probably due to the differences in their volatility and the equilibrium constants for the analyte/fiber coating. In order to overcome this issue, a new optimization approach was proposed based on a combination of extraction modes and extraction temperatures in a single extraction procedure. The final optimized procedure was: 48min of extraction in direct immersion mode with the sample maintained at 80°C followed by a further 32min of headspace extraction with the sample temperature kept at 10°C. The proposed procedure was compared with conventional methods based on the use of a single extraction mode and temperature (80min of headspace extraction at 60°C or 80min of direct immersion extraction at 50°C). The newly proposed method was shown to be more attractive as it extracted higher amounts of both semi-volatile and volatile compounds in a single extraction procedure compared to the conventional approaches. The optimized method was validated and excellent results were obtained.
Source:Journal of Chromatography A, Volume 1233
Joyce Nunes Bianchin, Giuliana Nardini, Josias Merib, Adriana Neves Dias, Edmar Martendal, Eduardo Carasek
This study proposes a new optimization approach for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene isomers (BTEX) from water samples using the solid-phase microextraction technique followed by gas chromatography–mass spectrometry (GC–MS) separation and detection. The objective of the study was to achieve compromise extraction conditions, suitable for all semi-volatile and volatile compounds, under which the amount extracted is maximized for all analytes. This was achieved by careful optimization of the fiber coating, salting-out effect, extraction time and temperature and extraction mode (headspace or direct immersion). With the optimized fiber coating – PDMS/DVB 65μm – the other selected factors were optimized using a response surface methodology through central composite designs. As expected, the optimized results for each class of analytes varied significantly, probably due to the differences in their volatility and the equilibrium constants for the analyte/fiber coating. In order to overcome this issue, a new optimization approach was proposed based on a combination of extraction modes and extraction temperatures in a single extraction procedure. The final optimized procedure was: 48min of extraction in direct immersion mode with the sample maintained at 80°C followed by a further 32min of headspace extraction with the sample temperature kept at 10°C. The proposed procedure was compared with conventional methods based on the use of a single extraction mode and temperature (80min of headspace extraction at 60°C or 80min of direct immersion extraction at 50°C). The newly proposed method was shown to be more attractive as it extracted higher amounts of both semi-volatile and volatile compounds in a single extraction procedure compared to the conventional approaches. The optimized method was validated and excellent results were obtained.
Plasmid DNA partitioning and separation using poly(ethylene glycol)/poly(acrylate)/salt aqueous two-phase systems
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Hans-Olof Johansson, Tiago Matos, Juliana S. Luz, Eloi Feitosa, Carla C. Oliveira, Adalberto Pessoa, Leif Bülow, Folke Tjerneld
Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coli can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coli homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60–70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH.
Source:Journal of Chromatography A, Volume 1233
Hans-Olof Johansson, Tiago Matos, Juliana S. Luz, Eloi Feitosa, Carla C. Oliveira, Adalberto Pessoa, Leif Bülow, Folke Tjerneld
Phase diagrams of poly(ethylene glycol)/polyacrylate/Na2SO4 systems have been investigated with respect to polymer size and pH. Plasmid DNA from Escherichia coli can depending on pH and polymer molecular weight be directed to a poly(ethylene glycol) or to a polyacrylate-rich phase in an aqueous two-phase system formed by these polymers. Bovine serum albumin (BSA) and E. coli homogenate proteins can be directed opposite to the plasmid partitioning in these systems. Two bioseparation processes have been developed where in the final step the pDNA is partitioned to a salt-rich phase giving a total process yield of 60–70%. In one of them the pDNA is partitioned between the polyacrylate and PEG-phases in order to remove proteins. In a more simplified process the plasmid is partitioned to a PEG-phase and back-extracted into a Na2SO4-rich phase. The novel polyacrylate/PEG system allows a strong change of the partitioning between the phases with relatively small changes in composition or pH.
Determination of triazine herbicides in cereals using dynamic microwave-assisted extraction with solidification of floating organic drop followed by high-performance liquid chromatography
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Hui Wang, Guijie Li, Yiqun Zhang, Haiyan Chen, Qi Zhao, Weitao Song, Yang Xu, Haiyan Jin, Lan Ding
A simple and cost-effective method of dynamic microwave-assisted extraction (DMAE) combined with solidification of floating organic drop (SFO) was developed for determining the five triazine herbicides in cereals. The approach combines the advantages of DMAE and SFO technique, and up to 15 samples can be treated simultaneously in 16min. Firstly, triazine herbicides were extracted with 1mL of methanol containing 90μL of 1-dodecanol and following with 10mL of water under the action of microwave energy. After that, 1.5g sodium chloride was added into the obtained extract, and the mixture was centrifuged and cooled. The 1-dodecanol drop which contained the target analytes was solidified and transferred for analysis by HPLC-UV. Limits of detection of the five triazines obtained were in the range of 1.1–1.5ngg−1. Relative standard deviations of intra- and inter-day tests ranging from 5% to 7% were obtained. The method was successfully applied to the analysis of ten cereals and the recoveries of the triazines for the spiked samples were in the range of 80–102%. The proposed method is an alternative approach to the analysis of triazine herbicides in complex solid samples, being more rapid and simpler compared with the traditional extraction method.
Source:Journal of Chromatography A, Volume 1233
Hui Wang, Guijie Li, Yiqun Zhang, Haiyan Chen, Qi Zhao, Weitao Song, Yang Xu, Haiyan Jin, Lan Ding
A simple and cost-effective method of dynamic microwave-assisted extraction (DMAE) combined with solidification of floating organic drop (SFO) was developed for determining the five triazine herbicides in cereals. The approach combines the advantages of DMAE and SFO technique, and up to 15 samples can be treated simultaneously in 16min. Firstly, triazine herbicides were extracted with 1mL of methanol containing 90μL of 1-dodecanol and following with 10mL of water under the action of microwave energy. After that, 1.5g sodium chloride was added into the obtained extract, and the mixture was centrifuged and cooled. The 1-dodecanol drop which contained the target analytes was solidified and transferred for analysis by HPLC-UV. Limits of detection of the five triazines obtained were in the range of 1.1–1.5ngg−1. Relative standard deviations of intra- and inter-day tests ranging from 5% to 7% were obtained. The method was successfully applied to the analysis of ten cereals and the recoveries of the triazines for the spiked samples were in the range of 80–102%. The proposed method is an alternative approach to the analysis of triazine herbicides in complex solid samples, being more rapid and simpler compared with the traditional extraction method.
Separation and quantification of 15 carotenoids by reversed phase high performance liquid chromatography coupled to diode array detection with isosbestic wavelength approach
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
Kamila Mitrowska, Ursula Vincent, Christoph von Holst
The manuscript presents the development of a new reverse phase high performance liquid chromatography (RP-HPLC) photo diode array detection method allowing the separation and quantification of 15 carotenoids (adonirubin, adonixanthin, astaxanthin, astaxanthin dimethyl disuccinate, asteroidenone, beta-apo-8′-carotenal, beta-apo-8′-carotenoic acid ethyl ester, beta-carotene, canthaxanthin, capsanthin, citranaxanthin, echinenone, lutein, lycopene, and zeaxanthin), 10 of which are feed additives authorised within the European Union. The developed method allows for the reliable determination of the total carotenoid content in one run using the corresponding E-isomer as calibration standard while taking into account the E/Z-isomers composition. This is a key criterion for the application of the method, since for most of the analytes included in this study analytical standards are only available for the E-isomers. This goal was achieved by applying the isosbestic concept, in order to identify specific wavelengths, at which the absorption coefficients are identical for all stereoisomers concerned. The second target referred to the optimisation of the LC conditions. By means of an experimental design, an optimised RP-HPLC method was developed allowing for a sufficient chromatographic separation of all carotenoids. The selected method uses a Suplex pKb-100 HPLC column and applying a gradient with a mixture of acetonitrile, tert-butyl-methyl ether and water as mobile phases. The limits of detection and limits of quantification ranged from 0.06mgL−1 to 0.14mgL−1 and from 0.20mgL−1 to 0.48mgL−1, respectively.
Source:Journal of Chromatography A, Volume 1233
Kamila Mitrowska, Ursula Vincent, Christoph von Holst
The manuscript presents the development of a new reverse phase high performance liquid chromatography (RP-HPLC) photo diode array detection method allowing the separation and quantification of 15 carotenoids (adonirubin, adonixanthin, astaxanthin, astaxanthin dimethyl disuccinate, asteroidenone, beta-apo-8′-carotenal, beta-apo-8′-carotenoic acid ethyl ester, beta-carotene, canthaxanthin, capsanthin, citranaxanthin, echinenone, lutein, lycopene, and zeaxanthin), 10 of which are feed additives authorised within the European Union. The developed method allows for the reliable determination of the total carotenoid content in one run using the corresponding E-isomer as calibration standard while taking into account the E/Z-isomers composition. This is a key criterion for the application of the method, since for most of the analytes included in this study analytical standards are only available for the E-isomers. This goal was achieved by applying the isosbestic concept, in order to identify specific wavelengths, at which the absorption coefficients are identical for all stereoisomers concerned. The second target referred to the optimisation of the LC conditions. By means of an experimental design, an optimised RP-HPLC method was developed allowing for a sufficient chromatographic separation of all carotenoids. The selected method uses a Suplex pKb-100 HPLC column and applying a gradient with a mixture of acetonitrile, tert-butyl-methyl ether and water as mobile phases. The limits of detection and limits of quantification ranged from 0.06mgL−1 to 0.14mgL−1 and from 0.20mgL−1 to 0.48mgL−1, respectively.
Determination of parameters for the steric mass action model—A comparison between two approaches
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
A. Osberghaus, S. Hepbildikler, S. Nath, M. Haindl, E. von Lieres, J. Hubbuch
The application of mechanistic modeling for the optimization of chromatographic steps increased recently due to time efficiency of algorithms and rising calculation power. In the modeling of ion exchange chromatography steps, the sorption processes occurring on adsorbent particle surfaces can be simulated with the steric mass action (SMA) model introduced by Brooks and Cramer (1992) [14]. In this paper, two approaches for the determination of SMA parameters will be carried out and discussed concerning their specific experimental effort, quality of results, method differences, reasons for uncertainties and consequences for SMA parameter determination: Approach I: estimation of SMA parameters based on gradient and frontal experiments according to instructions in Brooks and Cramer (1992) [14] and Shukla et al. (1998) [16]. Approach II: application of an inverse method for parameter estimation, resulting in SMA parameters that induce a best fit of chromatographic data to a mechanistic model for column chromatography. These approaches for SMA parameter determination were carried out for three proteins (ribonuclease A, cytochrome c and lysozyme) at pH 5 and pH 7. The results were comparable and the order of parameter values and their relations to the chromatographic data similar. Nevertheless, differences in the complexity and effort of methods as well as the parameter values themselves were observed. The comparison of methods demonstrated that discrepancies depend mainly on model sensitivities and additional parameters influencing the calculations. However, the discrepancies do not affect predictivity; predictivity is high in both approaches. The approach based on an inverse method and the mechanistic model has the advantage that not only retention times but also complete elution profiles can be predicted. Thus, the inverse method based on a mechanistic model for column chromatography is the most comfortable way to establish highly predictive SMA parameters lending themselves for the optimization of chromatography steps and process control.
Source:Journal of Chromatography A, Volume 1233
A. Osberghaus, S. Hepbildikler, S. Nath, M. Haindl, E. von Lieres, J. Hubbuch
The application of mechanistic modeling for the optimization of chromatographic steps increased recently due to time efficiency of algorithms and rising calculation power. In the modeling of ion exchange chromatography steps, the sorption processes occurring on adsorbent particle surfaces can be simulated with the steric mass action (SMA) model introduced by Brooks and Cramer (1992) [14]. In this paper, two approaches for the determination of SMA parameters will be carried out and discussed concerning their specific experimental effort, quality of results, method differences, reasons for uncertainties and consequences for SMA parameter determination: Approach I: estimation of SMA parameters based on gradient and frontal experiments according to instructions in Brooks and Cramer (1992) [14] and Shukla et al. (1998) [16]. Approach II: application of an inverse method for parameter estimation, resulting in SMA parameters that induce a best fit of chromatographic data to a mechanistic model for column chromatography. These approaches for SMA parameter determination were carried out for three proteins (ribonuclease A, cytochrome c and lysozyme) at pH 5 and pH 7. The results were comparable and the order of parameter values and their relations to the chromatographic data similar. Nevertheless, differences in the complexity and effort of methods as well as the parameter values themselves were observed. The comparison of methods demonstrated that discrepancies depend mainly on model sensitivities and additional parameters influencing the calculations. However, the discrepancies do not affect predictivity; predictivity is high in both approaches. The approach based on an inverse method and the mechanistic model has the advantage that not only retention times but also complete elution profiles can be predicted. Thus, the inverse method based on a mechanistic model for column chromatography is the most comfortable way to establish highly predictive SMA parameters lending themselves for the optimization of chromatography steps and process control.
Hydrophilic interaction liquid chromatography of anthranilic acid-labelled oligosaccharides with a 4-aminobenzoic acid ethyl ester-labelled dextran hydrolysate internal standard
27 March 2012,
09:18:54
Publication year:
2012
Source:Journal of Chromatography A, Volume 1233
David C.A. Neville, Dominic S. Alonzi, Terry D. Butters
Hydrophilic interaction liquid chromatography (HILIC) of fluorescently labelled oligosaccharides is used in many laboratories to analyse complex oligosaccharide mixtures. Separations are routinely performed using a TSK gel-Amide 80 HPLC column, and retention times of different oligosaccharide species are converted to glucose unit (GU) values that are determined with reference to an external standard. However, if retention times were to be compared with an internal standard, consistent and more accurate GU values would be obtained. We present a method to perform internal standard-calibrated HILIC of fluorescently labelled oligosaccharides. The method relies on co-injection of 4-aminobenzoic acid ethyl ester (4-ABEE)-labelled internal standard and detection by UV absorption, with 2-AA (2-aminobenzoic acid)-labelled oligosaccharides. 4-ABEE is a UV chromophore and a fluorophore, but there is no overlap of the fluorescent spectrum of 4-ABEE with the commonly used fluorescent reagents. The dual nature of 4-ABEE allows for accurate calculation of the delay between UV and fluorescent signals when determining the GU values of individual oligosaccharides. The GU values obtained are inherently more accurate as slight differences in gradients that can influence retention are negated by use of an internal standard. Therefore, this paper provides the first method for determination of HPLC-derived GU values of fluorescently labelled oligosaccharides using an internal calibrant.
Source:Journal of Chromatography A, Volume 1233
David C.A. Neville, Dominic S. Alonzi, Terry D. Butters
Hydrophilic interaction liquid chromatography (HILIC) of fluorescently labelled oligosaccharides is used in many laboratories to analyse complex oligosaccharide mixtures. Separations are routinely performed using a TSK gel-Amide 80 HPLC column, and retention times of different oligosaccharide species are converted to glucose unit (GU) values that are determined with reference to an external standard. However, if retention times were to be compared with an internal standard, consistent and more accurate GU values would be obtained. We present a method to perform internal standard-calibrated HILIC of fluorescently labelled oligosaccharides. The method relies on co-injection of 4-aminobenzoic acid ethyl ester (4-ABEE)-labelled internal standard and detection by UV absorption, with 2-AA (2-aminobenzoic acid)-labelled oligosaccharides. 4-ABEE is a UV chromophore and a fluorophore, but there is no overlap of the fluorescent spectrum of 4-ABEE with the commonly used fluorescent reagents. The dual nature of 4-ABEE allows for accurate calculation of the delay between UV and fluorescent signals when determining the GU values of individual oligosaccharides. The GU values obtained are inherently more accurate as slight differences in gradients that can influence retention are negated by use of an internal standard. Therefore, this paper provides the first method for determination of HPLC-derived GU values of fluorescently labelled oligosaccharides using an internal calibrant.
Subscribe to:
Posts (Atom)