Selected papers from the latest issue:
Sample displacement chromatography as a method for purification of proteins and peptides from complex mixtures
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Martina Srajer Gajdosik, James Clifton, Djuro Josic
Sample displacement chromatography (SDC) in reversed-phase and ion-exchange modes was introduced approximately twenty years ago. This method takes advantage of relative binding affinities of components in a sample mixture. During loading, there is a competition among different sample components for the sorption on the surface of the stationary phase. SDC was first used for the preparative purification of proteins. Later, it was demonstrated that this kind of chromatography can also be performed in ion-exchange, affinity and hydrophobic-interaction mode. It has also been shown that SDC can be performed on monoliths and membrane-based supports in both analytical and preparative scale. Recently, SDC in ion-exchange and hydrophobic interaction mode was also employed successfully for the removal of trace proteins from monoclonal antibody preparations and for the enrichment of low abundance proteins from human plasma. In this review, the principals of SDC are introduced, and the potential for separation of proteins and peptides in micro-analytical, analytical and preparative scale is discussed.
Source:Journal of Chromatography A, Volume 1239
Martina Srajer Gajdosik, James Clifton, Djuro Josic
Sample displacement chromatography (SDC) in reversed-phase and ion-exchange modes was introduced approximately twenty years ago. This method takes advantage of relative binding affinities of components in a sample mixture. During loading, there is a competition among different sample components for the sorption on the surface of the stationary phase. SDC was first used for the preparative purification of proteins. Later, it was demonstrated that this kind of chromatography can also be performed in ion-exchange, affinity and hydrophobic-interaction mode. It has also been shown that SDC can be performed on monoliths and membrane-based supports in both analytical and preparative scale. Recently, SDC in ion-exchange and hydrophobic interaction mode was also employed successfully for the removal of trace proteins from monoclonal antibody preparations and for the enrichment of low abundance proteins from human plasma. In this review, the principals of SDC are introduced, and the potential for separation of proteins and peptides in micro-analytical, analytical and preparative scale is discussed.
Visualisation of J-type counter-current chromatography: A route to understand hydrodynamic phase distribution and retention
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Yue Hugh Guan, Remco N.A.M. van den Heuvel, Ying-Ping Zhuang
This paper has addressed decade sought-after questions on phase bilateral distribution and stationary phase retention in any J-type high-speed counter-current chromatographic (CCC) centrifuge. Using a 2-D spiral column operated on such a CCC device and an aqueous two-phase system, this work systematically observed the phase interaction during transitional period and at dynamic equilibration under stroboscopic illumination. The experimental results thus obtained were used to examine the effects of the liquid–solid friction force, tangential centrifugal force, and physical properties of the two-phase system on hydrodynamic phase behaviour. We identified that (a) density difference between lower and upper phases is the critical factor to cause unusual phase bilateral distribution in the 2-D spiral column and (b) interfacial tension (manifested primarily as phase settling time) of any two-phase system is the critical factor in explaining inability to retain stationary phase in 3-D helical column and, for certain flow modes, in the 2-D spiral column. This work thus has extended or modified the well-established rule-of-thumb for operating J-type CCC devices and our conclusions can accommodate virtually all the anomalies concerning both hydrophobic and hydrophilic phase systems. To this end, this work has not only documented valuable experimental evidences for directly observing phase behaviour in a CCC column, but also finally resolved fundamentally vital issues on bilateral phase distribution orientation and stationary phase retention in 2-D spiral and 3-D helical CCC columns. Revised recommendations to end users of this technology could thus be derived out of the essence of the present work presumably following further experimental validation and a consensus in the CCC R&D and manufacturing circle.
Source:Journal of Chromatography A, Volume 1239
Yue Hugh Guan, Remco N.A.M. van den Heuvel, Ying-Ping Zhuang
This paper has addressed decade sought-after questions on phase bilateral distribution and stationary phase retention in any J-type high-speed counter-current chromatographic (CCC) centrifuge. Using a 2-D spiral column operated on such a CCC device and an aqueous two-phase system, this work systematically observed the phase interaction during transitional period and at dynamic equilibration under stroboscopic illumination. The experimental results thus obtained were used to examine the effects of the liquid–solid friction force, tangential centrifugal force, and physical properties of the two-phase system on hydrodynamic phase behaviour. We identified that (a) density difference between lower and upper phases is the critical factor to cause unusual phase bilateral distribution in the 2-D spiral column and (b) interfacial tension (manifested primarily as phase settling time) of any two-phase system is the critical factor in explaining inability to retain stationary phase in 3-D helical column and, for certain flow modes, in the 2-D spiral column. This work thus has extended or modified the well-established rule-of-thumb for operating J-type CCC devices and our conclusions can accommodate virtually all the anomalies concerning both hydrophobic and hydrophilic phase systems. To this end, this work has not only documented valuable experimental evidences for directly observing phase behaviour in a CCC column, but also finally resolved fundamentally vital issues on bilateral phase distribution orientation and stationary phase retention in 2-D spiral and 3-D helical CCC columns. Revised recommendations to end users of this technology could thus be derived out of the essence of the present work presumably following further experimental validation and a consensus in the CCC R&D and manufacturing circle.
High-throughput determination of adsorption equilibria for chromatographic oligosaccharide separations
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Sreekanth Chilamkurthi, Jan-Hein Willemsen, Luuk A.M. van der Wielen, Edwin Poiesz, Marcel Ottens
Adsorption equilibria of the saccharides d-glucose, d-galactose, l-arabinose, lactose and a sugar acid were measured on gel-type sulfonated poly (styrene-co-divinylbenzene) strong cation exchange resins in a high-throughput (HT) 96-well plate batch uptake mode using a pipetting robot at 25°C. Four different ionic forms, Ca2+, K+, Na+, and H+ were used. Single component adsorption isotherms were determined in a concentration range of 10–240mgml−1. Multicomponent experiments were performed to investigate competitive adsorption in a concentration range of 10–120mgml−1. A qualitative investigation on competitive and cooperative effects was performed. All sugar isotherms showed a linear behavior except for the sugar acid which showed an unfavorable (anti-Langmuir) behavior in the high concentration ranges. Selectivity values were determined from the binary mixture partition coefficient (K) values of each component. This HT 96-well plate batch uptake method proves to be less laborious and consumes less time and material compared to the frontal analysis and adsorption–desorption methods where column experimentation is used. Ternary mixture separation of arabinose and the sugar acid from glucose showed K+ and Ca2+ loaded resins having the best selectivity (DIAION Ca2+ 2.01 and 1.78 for l-arabinose/d-glucose and sugar acid/l-arabinose respectively), similarly Purolite K+ loaded resin for the lactose separation from glucose and galactose (1.17 for lactose/d-glucose). Column experiments were performed to validate the batch uptake experiments. The static binding results could easily be translated to the column experiments with good agreement. Finally, adding to the validity of the approach, binary and ternary fixed-bed experiments were well described by a dynamic mathematical chromatographic model using the parameters obtained from the binary-component isotherm data.
Source:Journal of Chromatography A, Volume 1239
Sreekanth Chilamkurthi, Jan-Hein Willemsen, Luuk A.M. van der Wielen, Edwin Poiesz, Marcel Ottens
Adsorption equilibria of the saccharides d-glucose, d-galactose, l-arabinose, lactose and a sugar acid were measured on gel-type sulfonated poly (styrene-co-divinylbenzene) strong cation exchange resins in a high-throughput (HT) 96-well plate batch uptake mode using a pipetting robot at 25°C. Four different ionic forms, Ca2+, K+, Na+, and H+ were used. Single component adsorption isotherms were determined in a concentration range of 10–240mgml−1. Multicomponent experiments were performed to investigate competitive adsorption in a concentration range of 10–120mgml−1. A qualitative investigation on competitive and cooperative effects was performed. All sugar isotherms showed a linear behavior except for the sugar acid which showed an unfavorable (anti-Langmuir) behavior in the high concentration ranges. Selectivity values were determined from the binary mixture partition coefficient (K) values of each component. This HT 96-well plate batch uptake method proves to be less laborious and consumes less time and material compared to the frontal analysis and adsorption–desorption methods where column experimentation is used. Ternary mixture separation of arabinose and the sugar acid from glucose showed K+ and Ca2+ loaded resins having the best selectivity (DIAION Ca2+ 2.01 and 1.78 for l-arabinose/d-glucose and sugar acid/l-arabinose respectively), similarly Purolite K+ loaded resin for the lactose separation from glucose and galactose (1.17 for lactose/d-glucose). Column experiments were performed to validate the batch uptake experiments. The static binding results could easily be translated to the column experiments with good agreement. Finally, adding to the validity of the approach, binary and ternary fixed-bed experiments were well described by a dynamic mathematical chromatographic model using the parameters obtained from the binary-component isotherm data.
Impact of the limitations of state-of-the-art micro-fabrication processes on the performance of pillar array columns for liquid chromatography
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Jeff Op de Beeck, Wim De Malsche, Deniz S. Tezcan, Piet De Moor, Gert Desmet
We report on the practical limitations of the current state-of-the-art in micro-fabrication technology to produce the small pillar sizes that are needed to obtain high efficiency pillar array columns. For this purpose, nine channels with a different pillar diameter, ranging from 5 to 0.5μm were fabricated using state-of the-art deep-UV lithography and deep reactive ion etching (DRIE) etching technology. The obtained results strongly deviated from the theoretically expected trend, wherein the minimal plate height (H min) would reduce linearly with the pillar diameter. The minimal plate height decreases from 1.7 to 1.2μm when going from 4.80 to 3.81μm diameter pillars, but as the dimensions are further reduced, the minimal plate heights rise again to values around 2μm. The smallest pillar diameter even produced the worst minimal plate height (4μm). An in-depth scanning electron microscopy (SEM) inspection of the different channels clearly reveals that these findings can be attributed to the micro-fabrication limitations that are inevitably encountered when exploring the limits of deep-UV lithography and DRIE etching processes. When the target dimensions of the design approach the etching resolution limits, the band broadening increases in a strongly non-linear way with the decreased pillar dimensions. This highly non-linear relationship can be understood from first principles: when the machining error is of the order of 100–200nm and when the target design size for the inter-pillar distance is of the order of 250nm, this inevitably leads to pores that will range in size between 50 and 450nm that we want to highlight with our paper highly non-linear relationship. This highly non-linear relationship can be understood from first principles: when the machining error is of the order of 100–200nm and when the target design size for the inter-pillar distance is of the order of 250nm, this inevitably leads to pores that will range in size between 50 and 450nm.
Source:Journal of Chromatography A, Volume 1239
Jeff Op de Beeck, Wim De Malsche, Deniz S. Tezcan, Piet De Moor, Gert Desmet
We report on the practical limitations of the current state-of-the-art in micro-fabrication technology to produce the small pillar sizes that are needed to obtain high efficiency pillar array columns. For this purpose, nine channels with a different pillar diameter, ranging from 5 to 0.5μm were fabricated using state-of the-art deep-UV lithography and deep reactive ion etching (DRIE) etching technology. The obtained results strongly deviated from the theoretically expected trend, wherein the minimal plate height (H min) would reduce linearly with the pillar diameter. The minimal plate height decreases from 1.7 to 1.2μm when going from 4.80 to 3.81μm diameter pillars, but as the dimensions are further reduced, the minimal plate heights rise again to values around 2μm. The smallest pillar diameter even produced the worst minimal plate height (4μm). An in-depth scanning electron microscopy (SEM) inspection of the different channels clearly reveals that these findings can be attributed to the micro-fabrication limitations that are inevitably encountered when exploring the limits of deep-UV lithography and DRIE etching processes. When the target dimensions of the design approach the etching resolution limits, the band broadening increases in a strongly non-linear way with the decreased pillar dimensions. This highly non-linear relationship can be understood from first principles: when the machining error is of the order of 100–200nm and when the target design size for the inter-pillar distance is of the order of 250nm, this inevitably leads to pores that will range in size between 50 and 450nm that we want to highlight with our paper highly non-linear relationship. This highly non-linear relationship can be understood from first principles: when the machining error is of the order of 100–200nm and when the target design size for the inter-pillar distance is of the order of 250nm, this inevitably leads to pores that will range in size between 50 and 450nm.
A validated ultra-high performance liquid chromatography coupled to high resolution mass spectrometry analysis for the simultaneous quantification of the three known boar taint compounds
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
K.M. Bekaert, J. Vanden Bussche, S. François, F.A.M. Tuyttens, H.F. De Brabander, F. Vandendriessche, L. Vanhaecke
Boar taint is an off-odour that can occur when meat or fat from entire male pigs is heated. Most of the currently available analytical methods are not capable of detecting the three known boar taint compounds (indole, skatole and androstenone) simultaneously, which renders their analysis often labour-intensive and time-consuming as separate analyses are required. In this study a validated U-HPLC–HR-Orbitrap-MS analysis method is described for the quantitative determination of the three boar taint compounds in fat. The sample pre-treatment involves a melting step followed by extraction with methanol and clean-up consisting of a freezing step and solid phase extraction (HLB cartridges). The analytes are then chromatographically separated and detected with an Exactive™ high-resolution mass spectrometer. Due to the absence of guidelines for the analysis of boar taint in fat, the Commission Decision 2002/657/EC [18] and ISO 17025 [19] guidelines were used as guideline for validation of the developed detection method. This resulted in limits of detection and limits of quantification between 2.5 and 7μgkg−1 and between 5 and 10μgkg−1 for the three compounds, respectively, which is far below the threshold values set at 100μgL−1 for indole, 200μgL−1 for skatole and 1000μgL−1 for androstenone in pig fat samples. The method obtained for the three compounds a repeatability (RSD) lower then 12.7% and a within-laboratory reproducibility (RSD) lower than 16.9%. The recovery of the three compounds ranged between 99 and 112 and an excellent linearity (R 2 ≥0.99) was found. In the future, this method may be extended with other compounds that turn out to be correlated with boar taint.
Source:Journal of Chromatography A, Volume 1239
K.M. Bekaert, J. Vanden Bussche, S. François, F.A.M. Tuyttens, H.F. De Brabander, F. Vandendriessche, L. Vanhaecke
Boar taint is an off-odour that can occur when meat or fat from entire male pigs is heated. Most of the currently available analytical methods are not capable of detecting the three known boar taint compounds (indole, skatole and androstenone) simultaneously, which renders their analysis often labour-intensive and time-consuming as separate analyses are required. In this study a validated U-HPLC–HR-Orbitrap-MS analysis method is described for the quantitative determination of the three boar taint compounds in fat. The sample pre-treatment involves a melting step followed by extraction with methanol and clean-up consisting of a freezing step and solid phase extraction (HLB cartridges). The analytes are then chromatographically separated and detected with an Exactive™ high-resolution mass spectrometer. Due to the absence of guidelines for the analysis of boar taint in fat, the Commission Decision 2002/657/EC [18] and ISO 17025 [19] guidelines were used as guideline for validation of the developed detection method. This resulted in limits of detection and limits of quantification between 2.5 and 7μgkg−1 and between 5 and 10μgkg−1 for the three compounds, respectively, which is far below the threshold values set at 100μgL−1 for indole, 200μgL−1 for skatole and 1000μgL−1 for androstenone in pig fat samples. The method obtained for the three compounds a repeatability (RSD) lower then 12.7% and a within-laboratory reproducibility (RSD) lower than 16.9%. The recovery of the three compounds ranged between 99 and 112 and an excellent linearity (R 2 ≥0.99) was found. In the future, this method may be extended with other compounds that turn out to be correlated with boar taint.
Preparation and characterization of hybrid-silica monolithic column with mixed-mode of hydrophilic and strong anion-exchange interactions for pressurized capillary electrochromatography
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Xiao Wang, Yanqiong Zheng, Chunyuan Zhang, Yanzhong Yang, Xucong Lin, Guihua Huang, Zenghong Xie
A novel organic-silica hybrid monolithic stationary phase with a mixed-mode of hydrophilic and strong anion-exchange interactions (HI-SAX) was prepared with a modified “one-pot” process of functional monomers and alkoxysilanes. Using a hydrosoluble initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AIBA), the homogeneous prepolymerization system of this hybrid monolith was successfully obtained by a simple operation. The polycondensation of alkoxysilanes (tetramethoxysilane (TMOS) and vinyl-trimethoxysilane (VTMS)) and the in situ copolymerization of a quaternary ammonium group-containing acrylic monomer ([2-(acryloyloxy)ethyl] trimethyl ammonium methyl sulfate (AETA)) on the precondensed siloxanes were achieved. The morphologies of the hybrid-silica monolithic matrixes were observed by SEM, and the performances of the organic-silica hybrid monolithic columns were investigated by pressurized capillary electrochromatography. The mechanical stability and reproducibility of the obtained hybrid monolithic column preformed acceptable. Both hydrophilic interaction chromatography mechanism and strong anion-exchanged interaction were investigated. A mixed mode of HI-SAX was obtained for the analysis of nucleotides with a good resolution, and the separation of polar and basic nucleic acid bases and nucleosides was also achieved without peak tailing.
Source:Journal of Chromatography A, Volume 1239
Xiao Wang, Yanqiong Zheng, Chunyuan Zhang, Yanzhong Yang, Xucong Lin, Guihua Huang, Zenghong Xie
A novel organic-silica hybrid monolithic stationary phase with a mixed-mode of hydrophilic and strong anion-exchange interactions (HI-SAX) was prepared with a modified “one-pot” process of functional monomers and alkoxysilanes. Using a hydrosoluble initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AIBA), the homogeneous prepolymerization system of this hybrid monolith was successfully obtained by a simple operation. The polycondensation of alkoxysilanes (tetramethoxysilane (TMOS) and vinyl-trimethoxysilane (VTMS)) and the in situ copolymerization of a quaternary ammonium group-containing acrylic monomer ([2-(acryloyloxy)ethyl] trimethyl ammonium methyl sulfate (AETA)) on the precondensed siloxanes were achieved. The morphologies of the hybrid-silica monolithic matrixes were observed by SEM, and the performances of the organic-silica hybrid monolithic columns were investigated by pressurized capillary electrochromatography. The mechanical stability and reproducibility of the obtained hybrid monolithic column preformed acceptable. Both hydrophilic interaction chromatography mechanism and strong anion-exchanged interaction were investigated. A mixed mode of HI-SAX was obtained for the analysis of nucleotides with a good resolution, and the separation of polar and basic nucleic acid bases and nucleosides was also achieved without peak tailing.
Hybrid monolithic columns with nanoparticles incorporated for capillary electrochromatography
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Wen Lei, Ling-Yi Zhang, Li Wan, Bian-Fang Shi, Yan-Qin Wang, Wei-Bing Zhang
The core–shell silica nanoparticles Fe3O4@SiO2/NH2, wormlike and hexagonal SBA-15 silica were incorporated into polymethacrylate monolithic columns containing butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA), respectively to develop novel stationary phases with mixing mechanism of reverse phase and ion exchange. Experimental conditions including types of nanoparticles, dispersion pattern, nanoparticles concentration, column placement mode, and reaction temperature were optimized for simple and stable column preparation. The poly(BMA-EDMA-Fe3O4@SiO2/NH2) and poly(BMA-EDMA-SBA-15/NH2) (both wormlike and hexagonal shape nanoparticles) monolithic columns were evaluated with mixture of organic acids as sample in capillary electrochromatography (CEC) mode and the relative column efficiency reaches 290,000plates/m. The results indicate that the incorporation of nanoparticles with various shapes enhances both selectivity and column efficiency due to high specific surface area of nanoparticles and mixing separation mechanism. In addition, poly(BMA-EDMA-Fe3O4@SiO2/NH2) monolith capillary column was applied to separation of aqueous extract of rhizoma gastrodiae and showed great potential in the method development of complex samples.
Source:Journal of Chromatography A, Volume 1239
Wen Lei, Ling-Yi Zhang, Li Wan, Bian-Fang Shi, Yan-Qin Wang, Wei-Bing Zhang
The core–shell silica nanoparticles Fe3O4@SiO2/NH2, wormlike and hexagonal SBA-15 silica were incorporated into polymethacrylate monolithic columns containing butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA), respectively to develop novel stationary phases with mixing mechanism of reverse phase and ion exchange. Experimental conditions including types of nanoparticles, dispersion pattern, nanoparticles concentration, column placement mode, and reaction temperature were optimized for simple and stable column preparation. The poly(BMA-EDMA-Fe3O4@SiO2/NH2) and poly(BMA-EDMA-SBA-15/NH2) (both wormlike and hexagonal shape nanoparticles) monolithic columns were evaluated with mixture of organic acids as sample in capillary electrochromatography (CEC) mode and the relative column efficiency reaches 290,000plates/m. The results indicate that the incorporation of nanoparticles with various shapes enhances both selectivity and column efficiency due to high specific surface area of nanoparticles and mixing separation mechanism. In addition, poly(BMA-EDMA-Fe3O4@SiO2/NH2) monolith capillary column was applied to separation of aqueous extract of rhizoma gastrodiae and showed great potential in the method development of complex samples.
Evaluation of lifetime and analytical performance of gas chromatographic inlet septa for analysis of reactive semivolatile organic compounds
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Jessica Westland, Kari Organtini, Frank L. Dorman
A comparison of septum degradation data obtained from a variety of standard GC septa, including the Thermogreen™ LB-2, AG3 (Green), Thermolite®, BTO® and the Merlin Microseal™ were evaluated. This study was conducted to determine analytical system lifetime between inlet maintenance based on chromatographic performance of reactive compounds as a function of septum aging through repeated injections. It is widely accepted that gas chromatographic septa degrade relative to the operating temperature of the injector and also based on the physical interaction with the syringe needle. This interaction may cause shedding of particles which then accumulate in the injection port liner, or possibly on the GC column in rare cases. This will likely lead to reactive compound breakdown in the injection port of flash-vaporizing inlets and thus reduce the amount of time that an instrument may be operated between inlet maintenance. Evaluations of the septa were based on the performance of the organochlorine compounds, endrin and 4,4′-DDT. These two compounds act as general indicators for the overall inertness of the GC injector, and their performance may be used to extrapolate to the performance of many other compounds. The average lifetime in terms of the number of injections for the studied septa was determined to range from 151 injections to nearly 2000 injections, depending on the septum. These values were found to be repeatable within the same septa material, or within class. The injection lifetime was found to be statistically different between different septa, however, indicating that not all septa are equivalent in terms of their durability to repeated injections. Additionally, some septa were found to predominately cause degradation of endrin, while others were found to cause reactivity of 4,4′-DDT, indicating that a difference in septa material may cause differences in what types of compounds become reactive in the GC inlet.
Source:Journal of Chromatography A, Volume 1239
Jessica Westland, Kari Organtini, Frank L. Dorman
A comparison of septum degradation data obtained from a variety of standard GC septa, including the Thermogreen™ LB-2, AG3 (Green), Thermolite®, BTO® and the Merlin Microseal™ were evaluated. This study was conducted to determine analytical system lifetime between inlet maintenance based on chromatographic performance of reactive compounds as a function of septum aging through repeated injections. It is widely accepted that gas chromatographic septa degrade relative to the operating temperature of the injector and also based on the physical interaction with the syringe needle. This interaction may cause shedding of particles which then accumulate in the injection port liner, or possibly on the GC column in rare cases. This will likely lead to reactive compound breakdown in the injection port of flash-vaporizing inlets and thus reduce the amount of time that an instrument may be operated between inlet maintenance. Evaluations of the septa were based on the performance of the organochlorine compounds, endrin and 4,4′-DDT. These two compounds act as general indicators for the overall inertness of the GC injector, and their performance may be used to extrapolate to the performance of many other compounds. The average lifetime in terms of the number of injections for the studied septa was determined to range from 151 injections to nearly 2000 injections, depending on the septum. These values were found to be repeatable within the same septa material, or within class. The injection lifetime was found to be statistically different between different septa, however, indicating that not all septa are equivalent in terms of their durability to repeated injections. Additionally, some septa were found to predominately cause degradation of endrin, while others were found to cause reactivity of 4,4′-DDT, indicating that a difference in septa material may cause differences in what types of compounds become reactive in the GC inlet.
Determination of RNA degradation by capillary electrophoresis with cyan light-emitted diode-induced fluorescence
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1239
Tzu-Hsueh Yang, Po-Ling Chang
RNA integrity plays an important role in RNA studies because poor RNA quality may have a great impact on downstream methodologies. This study proposes a cost-effective, rapid, and sensitive method for determining RNA integrity based on capillary electrophoresis that utilizes a cyan light-emitted diode-induced fluorescence as a separation tool. The capillary was initially coated with 0.1% Poly(vinylpyrrolidone) (M ave 1,300,000Da) to reduce electroosmotic flow and avoid RNA adsorption. When the capillary was filled with 0.4% poly(ethylene) oxide (M ave 4,000,000) and a nucleic acid-specific fluorescent dye, SYTO 9, the baseline separation of the 18S and 28S ribosomal RNAs (rRNAs) in total RNA was accomplished within 15min. The lowest detectable concentration for the 18S and 28S rRNAs was estimated to be 50pg/μL. Some peaks longer than the 28S rRNA that migrated slowly were observed as long as the initial total RNA concentration was optimized. The temperature-induced degradation of the large RNA fragments (longer than the 28S rRNA) was faster than that of 18S rRNA and 28S rRNA. These large RNA fragments may serve as a promising marker for testing RNA integrity compared to the traditional method.
Source:Journal of Chromatography A, Volume 1239
Tzu-Hsueh Yang, Po-Ling Chang
RNA integrity plays an important role in RNA studies because poor RNA quality may have a great impact on downstream methodologies. This study proposes a cost-effective, rapid, and sensitive method for determining RNA integrity based on capillary electrophoresis that utilizes a cyan light-emitted diode-induced fluorescence as a separation tool. The capillary was initially coated with 0.1% Poly(vinylpyrrolidone) (M ave 1,300,000Da) to reduce electroosmotic flow and avoid RNA adsorption. When the capillary was filled with 0.4% poly(ethylene) oxide (M ave 4,000,000) and a nucleic acid-specific fluorescent dye, SYTO 9, the baseline separation of the 18S and 28S ribosomal RNAs (rRNAs) in total RNA was accomplished within 15min. The lowest detectable concentration for the 18S and 28S rRNAs was estimated to be 50pg/μL. Some peaks longer than the 28S rRNA that migrated slowly were observed as long as the initial total RNA concentration was optimized. The temperature-induced degradation of the large RNA fragments (longer than the 28S rRNA) was faster than that of 18S rRNA and 28S rRNA. These large RNA fragments may serve as a promising marker for testing RNA integrity compared to the traditional method.
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Juan A. Asenjo, Barbara A. Andrews
Aqueous two-phase systems (ATPS) that are formed by mixing a polymer (usually polyethylene glycol, PEG) and a salt (e.g. phosphate, sulphate or citrate) or two polymers, and water can be effectively used for the separation and purification of proteins. The partitioning between both phases is dependent on the surface properties of the proteins and on the composition of the two phase system as has been recently reviewed by Asenjo and Andrews [1]. This paper analyses and reviews some elements that are important for implementation of these processes which are related to phase separation and continuous processing of ATPS. Phase separation for ATPS formed by PEG and salts has been studied and has been found to depend on which of the phases is continuous. Profiles of dispersion heights can be represented as a fraction of the initial height and are independent of the dimensions of the separator. This is important for the design of large scale aqueous two-phase separations. The kinetics of phase separation has been investigated as a function of the physical properties of the system. The settling rate is a crucial parameter for equipment design and it has been studied as a function of viscosity and density of the phases as well as the interfacial tension between them. Correlations that describe the rate of phase separation have been developed. Working in a continuous bottom-phase region is advantageous to ensure fast separation. A mathematical model to describe the continuous, study state operation of these systems has been investigated. Two simulations to show the effect of phase ratio on purification have been carried out which clearly show the effectivity of using such models. The practical application of ATPS has been demonstrated in many cases including a number of industrial applications with excellent levels of purity and yield. Examples include the purification of α-amylase and the large scale “in situ” purification of IGF-1 carried out by Genentech. The production scale purification of chymosin from recombinant Aspergillus supernatant is the most successful industrial application of this technology. Other applications include the separation and purification of human α-antitrypsin from transgenic sheep milk, the purification of monoclonal antibodies, tPA from CHO supernatant and recombinant VLPs (virus like particles) from yeast cells.
Source:Journal of Chromatography A, Volume 1238
Juan A. Asenjo, Barbara A. Andrews
Aqueous two-phase systems (ATPS) that are formed by mixing a polymer (usually polyethylene glycol, PEG) and a salt (e.g. phosphate, sulphate or citrate) or two polymers, and water can be effectively used for the separation and purification of proteins. The partitioning between both phases is dependent on the surface properties of the proteins and on the composition of the two phase system as has been recently reviewed by Asenjo and Andrews [1]. This paper analyses and reviews some elements that are important for implementation of these processes which are related to phase separation and continuous processing of ATPS. Phase separation for ATPS formed by PEG and salts has been studied and has been found to depend on which of the phases is continuous. Profiles of dispersion heights can be represented as a fraction of the initial height and are independent of the dimensions of the separator. This is important for the design of large scale aqueous two-phase separations. The kinetics of phase separation has been investigated as a function of the physical properties of the system. The settling rate is a crucial parameter for equipment design and it has been studied as a function of viscosity and density of the phases as well as the interfacial tension between them. Correlations that describe the rate of phase separation have been developed. Working in a continuous bottom-phase region is advantageous to ensure fast separation. A mathematical model to describe the continuous, study state operation of these systems has been investigated. Two simulations to show the effect of phase ratio on purification have been carried out which clearly show the effectivity of using such models. The practical application of ATPS has been demonstrated in many cases including a number of industrial applications with excellent levels of purity and yield. Examples include the purification of α-amylase and the large scale “in situ” purification of IGF-1 carried out by Genentech. The production scale purification of chymosin from recombinant Aspergillus supernatant is the most successful industrial application of this technology. Other applications include the separation and purification of human α-antitrypsin from transgenic sheep milk, the purification of monoclonal antibodies, tPA from CHO supernatant and recombinant VLPs (virus like particles) from yeast cells.
Selective transport of single protein molecules inside gold nanotubes
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Changbei Ma, Rui Han, Shengda Qi, Edward S. Yeung
Diffusion of single protein molecules inside gold nanotubes was investigated. 3-dimensional imaging was employed to locate the individual molecules inside the nanotubes as a function of time. As expected, larger proteins and smaller pore sizes resulted in smaller diffusion coefficients. Diffusion within PEG-coated gold nanotubes was found to be two orders of magnitude faster than in previously reported, similar sized untreated polycarbonate membrane pores, showing that adsorption was serious in the latter case. We further demonstrate chromatographic selectivity during transport by modifying the inner surface of the gold nanotubes with self-assembled monolayers of derivatized alkyl thiols. These results should be useful for designing membrane separations.
Source:Journal of Chromatography A, Volume 1238
Changbei Ma, Rui Han, Shengda Qi, Edward S. Yeung
Diffusion of single protein molecules inside gold nanotubes was investigated. 3-dimensional imaging was employed to locate the individual molecules inside the nanotubes as a function of time. As expected, larger proteins and smaller pore sizes resulted in smaller diffusion coefficients. Diffusion within PEG-coated gold nanotubes was found to be two orders of magnitude faster than in previously reported, similar sized untreated polycarbonate membrane pores, showing that adsorption was serious in the latter case. We further demonstrate chromatographic selectivity during transport by modifying the inner surface of the gold nanotubes with self-assembled monolayers of derivatized alkyl thiols. These results should be useful for designing membrane separations.
Simultaneous analysis of 10 trihalomethanes at nanogram per liter levels in water using solid-phase microextraction and gas chromatography mass-spectrometry
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Sebastien Allard, Jeffrey W.A. Charrois, Cynthia A. Joll, Anna Heitz
Trihalomethanes are predominantly formed during disinfection of water via reactions of the oxidant with natural organic matter. Even though chlorinated and brominated trihalomethanes are the most widespread organic contaminants in drinking water, when iodide is present in raw water iodinated trihalomethanes can also be formed. The formation of iodinated trihalomethanes can lead to taste and odor problems and is a potential health concern since they have been reported to be more toxic than their brominated or chlorinated analogs. Currently, there is no published standard analytical method for I-THMs in water. The analysis of 10 trihalomethanes in water samples in a single run is challenging because the iodinated trihalomethanes are found at very low concentrations (ng/L range), while the regulated chlorinated and brominated trihalomethanes are present at much higher concentrations (above μg/L). An automated headspace solid-phase microextraction technique, with a programmed temperature vaporizer inlet coupled with gas chromatography-mass spectrometry, was developed for routine analysis of 10 trihalomethanes i.e. bromo-, chloro- and iodo-trihalomethanes in water samples. The carboxen/polydimethylsiloxane/divinylbenzene fiber was found to be the most suitable. The optimization, linearity range, accuracy and precision of the method are discussed. The limits of detection range from 1ng/L to 20ng/L for iodoform and chloroform, respectively. Matrix effects in treated groundwater, surfacewater, seawater, and secondary wastewater were investigated and it was shown that the method is suitable for the analysis of trace levels of iodinated trihalomethanes in a wide range of waters. The method developed in the present study has the advantage of being rapid, simple and sensitive. A survey conducted throughout various process stages in an advanced water recycling plant showed the presence of iodinated trihalomethanes at ng/L levels.
Source:Journal of Chromatography A, Volume 1238
Sebastien Allard, Jeffrey W.A. Charrois, Cynthia A. Joll, Anna Heitz
Trihalomethanes are predominantly formed during disinfection of water via reactions of the oxidant with natural organic matter. Even though chlorinated and brominated trihalomethanes are the most widespread organic contaminants in drinking water, when iodide is present in raw water iodinated trihalomethanes can also be formed. The formation of iodinated trihalomethanes can lead to taste and odor problems and is a potential health concern since they have been reported to be more toxic than their brominated or chlorinated analogs. Currently, there is no published standard analytical method for I-THMs in water. The analysis of 10 trihalomethanes in water samples in a single run is challenging because the iodinated trihalomethanes are found at very low concentrations (ng/L range), while the regulated chlorinated and brominated trihalomethanes are present at much higher concentrations (above μg/L). An automated headspace solid-phase microextraction technique, with a programmed temperature vaporizer inlet coupled with gas chromatography-mass spectrometry, was developed for routine analysis of 10 trihalomethanes i.e. bromo-, chloro- and iodo-trihalomethanes in water samples. The carboxen/polydimethylsiloxane/divinylbenzene fiber was found to be the most suitable. The optimization, linearity range, accuracy and precision of the method are discussed. The limits of detection range from 1ng/L to 20ng/L for iodoform and chloroform, respectively. Matrix effects in treated groundwater, surfacewater, seawater, and secondary wastewater were investigated and it was shown that the method is suitable for the analysis of trace levels of iodinated trihalomethanes in a wide range of waters. The method developed in the present study has the advantage of being rapid, simple and sensitive. A survey conducted throughout various process stages in an advanced water recycling plant showed the presence of iodinated trihalomethanes at ng/L levels.
Aniline–silica nanocomposite as a novel solid phase microextraction fiber coating
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Habib Bagheri, Ali Roostaie
A new unbreakable solid phase microextraction (SPME) fiber coating based on aniline–silica nanocomposite was electrodeposited on a stainless steel wire. The electropolymerization process was carried out at a constant deposition potential, applied to the corresponding aqueous electrolyte containing aniline and silica nanoparticles. The scanning electron microscopy (SEM) images showed the non-smooth and the porous surface structure of the prepared nanocomposite. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some environmentally important polycyclic aromatic hydrocarbons (PAHs), as model compounds, from aqueous samples. Subsequently, the extracted analytes were transferred into a gas chromatography (GC) by thermal desorption. Parameters affecting the synthesizing and extraction processes including the voltage of power supply, the weight ratio of components, the time of electrodeposition, extraction time and temperature, the ionic strength, and desorption temperature and time were optimized. Eventually, the developed method was validated by gas chromatography–mass spectrometry (GC–MS). At the optimum conditions, the relative standard deviation (%RSD) values for a double distilled water spiked with the selected PAHs at 40ngL−1 were 6–13% (n =3) while the limit of detection (LOD) results were between 1 and 3ngL−1. The calibration graphs were linear in the concentration range from 20 to 4000ngL−1 (R 2 >0.995). Finally the developed method was applied to the analysis of Kalan dam, rain and tap water samples and the relative recovery values were found to be in the range of 76–109%, under optimized conditions. In addition, the synthesis of the nanocomposite coating was carried out conveniently while it is rather inexpensive, easy, simple, rapid and highly durable and can be used frequently.
Source:Journal of Chromatography A, Volume 1238
Habib Bagheri, Ali Roostaie
A new unbreakable solid phase microextraction (SPME) fiber coating based on aniline–silica nanocomposite was electrodeposited on a stainless steel wire. The electropolymerization process was carried out at a constant deposition potential, applied to the corresponding aqueous electrolyte containing aniline and silica nanoparticles. The scanning electron microscopy (SEM) images showed the non-smooth and the porous surface structure of the prepared nanocomposite. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some environmentally important polycyclic aromatic hydrocarbons (PAHs), as model compounds, from aqueous samples. Subsequently, the extracted analytes were transferred into a gas chromatography (GC) by thermal desorption. Parameters affecting the synthesizing and extraction processes including the voltage of power supply, the weight ratio of components, the time of electrodeposition, extraction time and temperature, the ionic strength, and desorption temperature and time were optimized. Eventually, the developed method was validated by gas chromatography–mass spectrometry (GC–MS). At the optimum conditions, the relative standard deviation (%RSD) values for a double distilled water spiked with the selected PAHs at 40ngL−1 were 6–13% (n =3) while the limit of detection (LOD) results were between 1 and 3ngL−1. The calibration graphs were linear in the concentration range from 20 to 4000ngL−1 (R 2 >0.995). Finally the developed method was applied to the analysis of Kalan dam, rain and tap water samples and the relative recovery values were found to be in the range of 76–109%, under optimized conditions. In addition, the synthesis of the nanocomposite coating was carried out conveniently while it is rather inexpensive, easy, simple, rapid and highly durable and can be used frequently.
Enhanced pressurized liquid extraction technique capable of analyzing polychlorodibenzo-p-dioxins, polychlorodibenzofurans, and polychlorobiphenyls in fish tissue
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Bikram Subedi, Sascha Usenko
A high-throughput enhanced pressurized liquid extraction technique was developed by incorporating pressurized liquid extraction and multiple cleanup techniques. USEPA methods of polychlorodibenzo-p-dioxins, polychlorodibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) analysis in fish tissue include independent silica gel, florisil, alumina, and carbopack/celite column cleanup techniques following extraction. Under the improved method, fish composites (∼10g) were extracted and cleaned simultaneously using alumina (∼10g), florisil (∼10g), silica gel (∼5g), celite (∼5g), and carbopack (∼0.5g). Clean extracts were concentrated and then analyzed by high resolution gas chromatography coupled with electron capture negative ionization mass spectrometry. Carbopack/celite within the extraction cell provided the analytical separation of dl-PCBs from PCDD/Fs, reducing potential molecular interferences. The average recoveries (n =3) of dl-PCBs in dichloromethane:hexane (1:1, v/v) extracts were 93±2.4% and PCDD/Fs in toluene extracts were 85±3.0%. The developed method was applied to measure the PCDD/Fs and dl-PCBs in catfish from San Jacinto River Waste Pits, a Superfund site in Houston, TX. The dl-PCBs were measured at 5.0–17,000pgg−1 ww. Sample preparation time and solvents were reduced as much as 95% and 65%, respectively, as compared to USEPA method 1613.
Source:Journal of Chromatography A, Volume 1238
Bikram Subedi, Sascha Usenko
A high-throughput enhanced pressurized liquid extraction technique was developed by incorporating pressurized liquid extraction and multiple cleanup techniques. USEPA methods of polychlorodibenzo-p-dioxins, polychlorodibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) analysis in fish tissue include independent silica gel, florisil, alumina, and carbopack/celite column cleanup techniques following extraction. Under the improved method, fish composites (∼10g) were extracted and cleaned simultaneously using alumina (∼10g), florisil (∼10g), silica gel (∼5g), celite (∼5g), and carbopack (∼0.5g). Clean extracts were concentrated and then analyzed by high resolution gas chromatography coupled with electron capture negative ionization mass spectrometry. Carbopack/celite within the extraction cell provided the analytical separation of dl-PCBs from PCDD/Fs, reducing potential molecular interferences. The average recoveries (n =3) of dl-PCBs in dichloromethane:hexane (1:1, v/v) extracts were 93±2.4% and PCDD/Fs in toluene extracts were 85±3.0%. The developed method was applied to measure the PCDD/Fs and dl-PCBs in catfish from San Jacinto River Waste Pits, a Superfund site in Houston, TX. The dl-PCBs were measured at 5.0–17,000pgg−1 ww. Sample preparation time and solvents were reduced as much as 95% and 65%, respectively, as compared to USEPA method 1613.
Biocompatible phosphatidylcholine bilayer coated on magnetic nanoparticles and their application in the extraction of several polycyclic aromatic hydrocarbons from environmental water and milk samples
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Shengxiao Zhang, Hongyun Niu, Yuanyuan Zhang, Junshen Liu, Yali Shi, Xiaole Zhang, Yaqi Cai
In this work, phosphatidylcholine (PC) was coated on magnetic nanoparticles to form lipid bilayer as solid-phase extraction (SPE) sorbents for the enrichment of polycyclic aromatic hydrocarbons (PAHs) from environmental water and milk samples. The lipid bilayer was coated on Fe3O4 nanoparticles using a modified dry lipid film hydration method. The resulted Fe3O4/PC could be readily isolated from solution with a magnet, and exhibited excellent adsorption performance to organic pollutants. Only 0.1g of sorbents was enough to extract PAHs from 500mL aqueous solution, and 6mL of acetonitrile was required to desorb them. The method was fast and relied on 10min extraction time and 5min magnetic separation. The proposed method was successfully applied to determine PAHs in some environmental water and milk samples. The detection limit was in the range of 0.2–0.6ngL−1. The recoveries of the spiked water samples ranged from 89% to 115% with relative standard deviations (RSD) varying from 1% to 8%. For spiked milk samples, RSD was satisfactory (1–9%), but the recoveries were relatively low (42–62%). We show the potentials of Fe3O4/PC sorbents in environmental water and biological sample analyses.
Source:Journal of Chromatography A, Volume 1238
Shengxiao Zhang, Hongyun Niu, Yuanyuan Zhang, Junshen Liu, Yali Shi, Xiaole Zhang, Yaqi Cai
In this work, phosphatidylcholine (PC) was coated on magnetic nanoparticles to form lipid bilayer as solid-phase extraction (SPE) sorbents for the enrichment of polycyclic aromatic hydrocarbons (PAHs) from environmental water and milk samples. The lipid bilayer was coated on Fe3O4 nanoparticles using a modified dry lipid film hydration method. The resulted Fe3O4/PC could be readily isolated from solution with a magnet, and exhibited excellent adsorption performance to organic pollutants. Only 0.1g of sorbents was enough to extract PAHs from 500mL aqueous solution, and 6mL of acetonitrile was required to desorb them. The method was fast and relied on 10min extraction time and 5min magnetic separation. The proposed method was successfully applied to determine PAHs in some environmental water and milk samples. The detection limit was in the range of 0.2–0.6ngL−1. The recoveries of the spiked water samples ranged from 89% to 115% with relative standard deviations (RSD) varying from 1% to 8%. For spiked milk samples, RSD was satisfactory (1–9%), but the recoveries were relatively low (42–62%). We show the potentials of Fe3O4/PC sorbents in environmental water and biological sample analyses.
Bifunctional ultrasound assisted extraction and determination of Elettaria cardamomum Maton essential oil
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Hassan Sereshti, Ahmad Rohanifar, Sadjad Bakhtiari, Soheila Samadi
A new hyphenated extraction method composed of ultrasound assisted extraction (UAE)-optimized ultrasound assisted emulsification microextraction (USAEME) was developed for the extraction and preconcentration of the essential oil of Elettaria cardamomum Maton. The essential oil was analyzed by gas chromatography–mass spectrometry (GC–MS) and optimization was performed using gas chromatography-flame ionization detection (GC-FID). Ultrasound played two different roles in the extraction of the essential oil. First, as a source of sufficient energy to break the oil-containing glands in order to release the oil, and second as an emulsifier to disperse the organic phase within water. The effective parameters (factors) of USAEME including volume of extraction solvent (C2H4Cl2), extraction temperature and ultrasonic time were optimized by using a central composite design (CCD). The optimal conditions were 120μL for extraction solvent volume, 32.5°C for temperature and 10.5min for ultrasonic time. The linear dynamic ranges (LDRs) were 0.01–50mgL−1 with the determination coefficients in the range of 0.9990–0.9999. The limits of detection (LODs) and the relative standard deviations (RSDs) were 0.001–0.007mgL−1 and 3.6–6.3%, respectively. The enrichment factors were 93–98. The main components of the extracted essential oil were α-terpenyl acetate (46.0%), 1,8-cineole (27.7%), linalool (5.3%), α-terpineol (4.0%), linalyl acetate (3.5%).
Source:Journal of Chromatography A, Volume 1238
Hassan Sereshti, Ahmad Rohanifar, Sadjad Bakhtiari, Soheila Samadi
A new hyphenated extraction method composed of ultrasound assisted extraction (UAE)-optimized ultrasound assisted emulsification microextraction (USAEME) was developed for the extraction and preconcentration of the essential oil of Elettaria cardamomum Maton. The essential oil was analyzed by gas chromatography–mass spectrometry (GC–MS) and optimization was performed using gas chromatography-flame ionization detection (GC-FID). Ultrasound played two different roles in the extraction of the essential oil. First, as a source of sufficient energy to break the oil-containing glands in order to release the oil, and second as an emulsifier to disperse the organic phase within water. The effective parameters (factors) of USAEME including volume of extraction solvent (C2H4Cl2), extraction temperature and ultrasonic time were optimized by using a central composite design (CCD). The optimal conditions were 120μL for extraction solvent volume, 32.5°C for temperature and 10.5min for ultrasonic time. The linear dynamic ranges (LDRs) were 0.01–50mgL−1 with the determination coefficients in the range of 0.9990–0.9999. The limits of detection (LODs) and the relative standard deviations (RSDs) were 0.001–0.007mgL−1 and 3.6–6.3%, respectively. The enrichment factors were 93–98. The main components of the extracted essential oil were α-terpenyl acetate (46.0%), 1,8-cineole (27.7%), linalool (5.3%), α-terpineol (4.0%), linalyl acetate (3.5%).
Rapid whole protein quantitation of staphylococcal enterotoxins A and B by liquid chromatography/mass spectrometry
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Isabel Sospedra, Carla Soler, Jordi Mañes, José Miguel Soriano
Staphylococcus aureus is an important pathogen and has been indicated as the fifth causative agent of food-borne human illness throughout the world. Staphylococcal enterotoxins (SEs) are toxic compounds excreted mainly by strains of S. aureus. Among these toxins, enterotoxins A (SEA) and B (SEB) are both of the most prevalent compounds in staphylococcal food poisoning. In this work, reverse phase liquid chromatography coupled to ESI mass spectrometry (LC–ESI/MS) has been applied for its rapid identification and quantification. Limit of detection (LOD) values were 0.5 and 0.2ng for SEA and SEB, respectively and limit of quantification (LOQ) value was 1ng for both enterotoxins. SEA and SEB have been analyzed as intact proteins in milk and fruit juices. Analytical methods are essential for routine monitoring purposes and safeguard public health and the proposed technique can detect and quantify successfully SEA and SEB in food samples.
Source:Journal of Chromatography A, Volume 1238
Isabel Sospedra, Carla Soler, Jordi Mañes, José Miguel Soriano
Staphylococcus aureus is an important pathogen and has been indicated as the fifth causative agent of food-borne human illness throughout the world. Staphylococcal enterotoxins (SEs) are toxic compounds excreted mainly by strains of S. aureus. Among these toxins, enterotoxins A (SEA) and B (SEB) are both of the most prevalent compounds in staphylococcal food poisoning. In this work, reverse phase liquid chromatography coupled to ESI mass spectrometry (LC–ESI/MS) has been applied for its rapid identification and quantification. Limit of detection (LOD) values were 0.5 and 0.2ng for SEA and SEB, respectively and limit of quantification (LOQ) value was 1ng for both enterotoxins. SEA and SEB have been analyzed as intact proteins in milk and fruit juices. Analytical methods are essential for routine monitoring purposes and safeguard public health and the proposed technique can detect and quantify successfully SEA and SEB in food samples.
A novel hydroquinidine imprinted microsphere using a chirality-matching N-Acryloyl-l-phenylalanine monomer for recognition of cinchona alkaloids
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Qi Zhou, Jing He, Youwen Tang, Zhiguang Xu, He Li, Chengcheng Kang, Jiabing Jiang
Using a combination of molecular imprinting technology and traditional chiral stationary phases, the synergistic effect between chiral monomer and chiral cavity of molecularly imprinted polymers in stereoselective recognition was investigated. We designed and synthesized an amino acid derivative to be used as a novel chiral functional monomer. Monodisperse molecularly imprinted core–shell microspheres using surface imprinting method on silica gel were prepared with hydroquinidine as the pseudo-template molecule for the resolution of cinchona alkaloids. The results showed a significant synergistic effect in stereoselective recognition, confirming our initial hypothesis. Furthermore, our computational simulation and experiments intensively support the hypothetical chiral recognition mechanism for the imprinted microspheres.
Source:Journal of Chromatography A, Volume 1238
Qi Zhou, Jing He, Youwen Tang, Zhiguang Xu, He Li, Chengcheng Kang, Jiabing Jiang
Using a combination of molecular imprinting technology and traditional chiral stationary phases, the synergistic effect between chiral monomer and chiral cavity of molecularly imprinted polymers in stereoselective recognition was investigated. We designed and synthesized an amino acid derivative to be used as a novel chiral functional monomer. Monodisperse molecularly imprinted core–shell microspheres using surface imprinting method on silica gel were prepared with hydroquinidine as the pseudo-template molecule for the resolution of cinchona alkaloids. The results showed a significant synergistic effect in stereoselective recognition, confirming our initial hypothesis. Furthermore, our computational simulation and experiments intensively support the hypothetical chiral recognition mechanism for the imprinted microspheres.
A priori selection of the mobile and stationary phase in centrifugal partition chromatography and counter-current chromatography
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Elisabeth Hopmann, Andreas Frey, Mirjana Minceva
The selection of the mobile and the stationary phase in support-free liquid–liquid chromatography (centrifugal partition chromatography and counter-current chromatography) is equivalent to a selection of a biphasic liquid system and its global composition. There is an immense number of choices of biphasic liquid systems. On one hand what makes this technique extremely versatile, on the other hand turns the selection of the appropriate system for a particular separation problem into a challenging and demanding task. In this work a systematic procedure for the selection of biphasic liquid systems for preparative scale separations is presented. The procedure is adaptable to the production scale requirements including production cost and safety. The experimental effort of different stages of the selection procedure is minimized by using a fully predictive method, the conductor-like screening model for real solvents (COSMO-RS). The COSMO-RS is used to assess properties relevant for the selection of a biphasic liquid system, such as the solute solubility and the partition coefficient.
Source:Journal of Chromatography A, Volume 1238
Elisabeth Hopmann, Andreas Frey, Mirjana Minceva
The selection of the mobile and the stationary phase in support-free liquid–liquid chromatography (centrifugal partition chromatography and counter-current chromatography) is equivalent to a selection of a biphasic liquid system and its global composition. There is an immense number of choices of biphasic liquid systems. On one hand what makes this technique extremely versatile, on the other hand turns the selection of the appropriate system for a particular separation problem into a challenging and demanding task. In this work a systematic procedure for the selection of biphasic liquid systems for preparative scale separations is presented. The procedure is adaptable to the production scale requirements including production cost and safety. The experimental effort of different stages of the selection procedure is minimized by using a fully predictive method, the conductor-like screening model for real solvents (COSMO-RS). The COSMO-RS is used to assess properties relevant for the selection of a biphasic liquid system, such as the solute solubility and the partition coefficient.
Band broadening in fast gradient high-performance liquid chromatography: Application to the second generation of 4.6mm I.D. silica monolithic columns
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Fabrice Gritti, Georges Guiochon
The sources of band broadening in fast gradient elution chromatography include the contributions of the tubings placed upstream the column, the isocratic migration of the sample that takes place in the column until the moment when the front of the gradient catches up with it, dispersion and mass transfer resistance during band migration under gradient elution to the column outlet, and dispersion in the tubings downstream the column to the detector. The measurements of all these contributions is meticulously described, analyzed, and applied to assess the kinetic performance of monolithic columns of the second generation (KGaA Merck) in gradient elution, at the highest possible speed at which they can be operated (t 0=25s at P =200bar). These results are compared to those provided by several 4.6mm × 100mm columns packed with sub-3μm core–shell particles (Kinetex, Phenomenex and Halo, Advanced Material Technologies) and by a 2.1mm × 100mm column packed with fully porous 1.7μm BEH particles (Waters). A RPLC checkout sample (Agilent) containing nine alkanophenones (molecular weights between 120 and 204g/mol) was used for this purpose. The mobile phase was a mixture of acetonitrile and water and the instrument, an optimized version of the 1290 Infinity HPLC system (Agilent). The results show that the overall peak capacity provided by this second generation of monolithic columns is nearly 30% smaller than that provided by commercial columns packed with sub-3 μm core–shell particles and 20% smaller than that provided by a narrow-bore column packed with sub-2μm fully porous particles. After isolating the sole band broadening contribution due to the gradient migration of the analytes along the columns, the BEH column proved to provide the highest resolution power (apparent average plate height, of 2μm), followed by the 2.6μm Kinetex particles (3.0μm), the Halo particles (3.2μm), and the second generation of 4.6mm I.D. monolithic columns (6.5μm). This work demonstrates that analysts have an urgent need for very high pressure liquid chromatographs having smaller dwell and extra-column volumes that those of the currently available instruments. The gradient elution peak capacity provided by the modern, narrow-diameter columns, which are short and highly efficient (plate heights of 3–4μm), is barely half what the column alone could produce if it were fitted to a perfect instrument. The other half of the peak capacity is just wasted by the instrument.
Source:Journal of Chromatography A, Volume 1238
Fabrice Gritti, Georges Guiochon
The sources of band broadening in fast gradient elution chromatography include the contributions of the tubings placed upstream the column, the isocratic migration of the sample that takes place in the column until the moment when the front of the gradient catches up with it, dispersion and mass transfer resistance during band migration under gradient elution to the column outlet, and dispersion in the tubings downstream the column to the detector. The measurements of all these contributions is meticulously described, analyzed, and applied to assess the kinetic performance of monolithic columns of the second generation (KGaA Merck) in gradient elution, at the highest possible speed at which they can be operated (t 0=25s at P =200bar). These results are compared to those provided by several 4.6mm × 100mm columns packed with sub-3μm core–shell particles (Kinetex, Phenomenex and Halo, Advanced Material Technologies) and by a 2.1mm × 100mm column packed with fully porous 1.7μm BEH particles (Waters). A RPLC checkout sample (Agilent) containing nine alkanophenones (molecular weights between 120 and 204g/mol) was used for this purpose. The mobile phase was a mixture of acetonitrile and water and the instrument, an optimized version of the 1290 Infinity HPLC system (Agilent). The results show that the overall peak capacity provided by this second generation of monolithic columns is nearly 30% smaller than that provided by commercial columns packed with sub-3 μm core–shell particles and 20% smaller than that provided by a narrow-bore column packed with sub-2μm fully porous particles. After isolating the sole band broadening contribution due to the gradient migration of the analytes along the columns, the BEH column proved to provide the highest resolution power (apparent average plate height, of 2μm), followed by the 2.6μm Kinetex particles (3.0μm), the Halo particles (3.2μm), and the second generation of 4.6mm I.D. monolithic columns (6.5μm). This work demonstrates that analysts have an urgent need for very high pressure liquid chromatographs having smaller dwell and extra-column volumes that those of the currently available instruments. The gradient elution peak capacity provided by the modern, narrow-diameter columns, which are short and highly efficient (plate heights of 3–4μm), is barely half what the column alone could produce if it were fitted to a perfect instrument. The other half of the peak capacity is just wasted by the instrument.
Computer assisted optimization of liquid chromatographic separations of small molecules using mixed-mode stationary phases
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Edgar Y. Ordoñez, José Benito Quintana, Rosario Rodil, Rafael Cela
Mixed-mode stationary phases are gaining adepts in liquid chromatography (LC) as more and more applications are published and new commercial columns appear in the market ought to their ability to retain and separate analytes with multiple functionalities. The increased number of adjustable variables gives these columns an enhanced value for the chromatographer, but, on the other hand, it complicates the process of developing satisfactory separations when complex samples must be analyzed. Thus, the availability of computer assisted methods development (CAMD) tools is highly desirable in this field. Therefore, the first specific tool for the CAMD of LC separations in mixed-mode columns is presented. The tool consists in two processes. The first one develops a retention model for peaks in a predefined experimental domain of pH and buffer concentration. In this domain, the retention as a function of the proportion of organic modifier is modeled using a two-stage re-calibration process departing from isocratic retention data and then, from gradient elutions. With this two-stage approach, reliability is gained. In the second process, the model is finally interpolated and used for the unattended optimization of the different possible elution modes available in these columns. This optimization process is driven by an evolutionary algorithm. The development and application of this new chemometrics tool is demonstrated by the optimization of a mixture of neutral and ionizable compounds. Hence, several different types of gradients were generated, showing a good agreement between simulated and experimental data, with retention time errors lower than 5% in most cases. On the other hand, classical CAMD tools, such as design of experiments, were unable to efficiently deal with mixed-mode optimizations, rendering errors above 30% for several compounds.
Source:Journal of Chromatography A, Volume 1238
Edgar Y. Ordoñez, José Benito Quintana, Rosario Rodil, Rafael Cela
Mixed-mode stationary phases are gaining adepts in liquid chromatography (LC) as more and more applications are published and new commercial columns appear in the market ought to their ability to retain and separate analytes with multiple functionalities. The increased number of adjustable variables gives these columns an enhanced value for the chromatographer, but, on the other hand, it complicates the process of developing satisfactory separations when complex samples must be analyzed. Thus, the availability of computer assisted methods development (CAMD) tools is highly desirable in this field. Therefore, the first specific tool for the CAMD of LC separations in mixed-mode columns is presented. The tool consists in two processes. The first one develops a retention model for peaks in a predefined experimental domain of pH and buffer concentration. In this domain, the retention as a function of the proportion of organic modifier is modeled using a two-stage re-calibration process departing from isocratic retention data and then, from gradient elutions. With this two-stage approach, reliability is gained. In the second process, the model is finally interpolated and used for the unattended optimization of the different possible elution modes available in these columns. This optimization process is driven by an evolutionary algorithm. The development and application of this new chemometrics tool is demonstrated by the optimization of a mixture of neutral and ionizable compounds. Hence, several different types of gradients were generated, showing a good agreement between simulated and experimental data, with retention time errors lower than 5% in most cases. On the other hand, classical CAMD tools, such as design of experiments, were unable to efficiently deal with mixed-mode optimizations, rendering errors above 30% for several compounds.
Comparison of various ternary simulated moving bed separation schemes by multi-objective optimization
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Gaurav Agrawal, Yoshiaki Kawajiri
Over the past decade, many modifications have been proposed in simulated moving bed (SMB) chromatography in order to effectively separate a binary mixture. However, the separation of multi-component mixtures using SMB is still one of the major challenges. In addition, the performance of SMB system highly depends on its operating conditions. Our study address this issue by formulating a multi-objective optimization problem that maximizes the productivity and purity of intermediate eluting component at the same time. A number of optimized isocractic ternary SMB operating schemes are compared both in terms of productivity and amount of desorbent to feed ratio. Furthermore, we propose a generalized full cycle (GFC) formulation based on superstructure formulation encompassing numerous operating schemes proposed in the literature. We also demonstrate that this approach has a potential to find the best ternary separation strategy among various alternatives.
Source:Journal of Chromatography A, Volume 1238
Gaurav Agrawal, Yoshiaki Kawajiri
Over the past decade, many modifications have been proposed in simulated moving bed (SMB) chromatography in order to effectively separate a binary mixture. However, the separation of multi-component mixtures using SMB is still one of the major challenges. In addition, the performance of SMB system highly depends on its operating conditions. Our study address this issue by formulating a multi-objective optimization problem that maximizes the productivity and purity of intermediate eluting component at the same time. A number of optimized isocractic ternary SMB operating schemes are compared both in terms of productivity and amount of desorbent to feed ratio. Furthermore, we propose a generalized full cycle (GFC) formulation based on superstructure formulation encompassing numerous operating schemes proposed in the literature. We also demonstrate that this approach has a potential to find the best ternary separation strategy among various alternatives.
Development of analysis of volatile polyfluorinated alkyl substances in indoor air using thermal desorption-gas chromatography–mass spectrometry
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Yaoxing Wu, Victor W.-C. Chang
The study attempts to utilize thermal desorption (TD) coupled with gas chromatography–mass spectrometry (GC–MS) for determination of indoor airborne volatile polyfluorinated alkyl substances (PFASs), including four fluorinated alcohols (FTOHs), two fluorooctane sulfonamides (FOSAs), and two fluorooctane sulfonamidoethanols (FOSEs). Standard stainless steel tubes of Tenax/Carbograph 1 TD were employed for low-volume sampling and exhibited minimal breakthrough of target analytes in sample collection. The method recoveries were in the range of 88–119% for FTOHs, 86–138% for FOSAs, exhibiting significant improvement compared with other existing air sampling methods. However, the widely reported high method recoveries of FOSEs were also observed (139–210%), which was probably due to the structural differences between FOSEs and internal standards. Method detection limit, repeatability, linearity, and accuracy were reported as well. The approach has been successfully applied to routine quantification of targeted PFASs in indoor environment of Singapore. The significantly shorter sampling time enabled the observation of variations of concentrations of targeted PFASs within different periods of a day, with higher concentration levels at night while ventilation systems were shut off. This indicated the existence of indoor sources and the importance of building ventilation and air conditioning system.
Source:Journal of Chromatography A, Volume 1238
Yaoxing Wu, Victor W.-C. Chang
The study attempts to utilize thermal desorption (TD) coupled with gas chromatography–mass spectrometry (GC–MS) for determination of indoor airborne volatile polyfluorinated alkyl substances (PFASs), including four fluorinated alcohols (FTOHs), two fluorooctane sulfonamides (FOSAs), and two fluorooctane sulfonamidoethanols (FOSEs). Standard stainless steel tubes of Tenax/Carbograph 1 TD were employed for low-volume sampling and exhibited minimal breakthrough of target analytes in sample collection. The method recoveries were in the range of 88–119% for FTOHs, 86–138% for FOSAs, exhibiting significant improvement compared with other existing air sampling methods. However, the widely reported high method recoveries of FOSEs were also observed (139–210%), which was probably due to the structural differences between FOSEs and internal standards. Method detection limit, repeatability, linearity, and accuracy were reported as well. The approach has been successfully applied to routine quantification of targeted PFASs in indoor environment of Singapore. The significantly shorter sampling time enabled the observation of variations of concentrations of targeted PFASs within different periods of a day, with higher concentration levels at night while ventilation systems were shut off. This indicated the existence of indoor sources and the importance of building ventilation and air conditioning system.
Chemometric analysis of gas chromatography with flame ionisation detection chromatograms: A novel method for classification of petroleum products
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
N.J. Nielsen, D. Ballabio, G. Tomasi, R. Todeschini, J.H. Christensen
Most oil characterisation procedures are time consuming, labour intensive and utilise only part of the acquired chemical information. Oil spill fingerprinting with multivariate data processing represents a fast and objective evaluation procedure, where the entire chromatographic profile is used. Methods for oil classification should be robust towards changes imposed on the spill fingerprint by short-term weathering, i.e. dissolution and evaporation processes in the hours following a spill. We propose a methodology for the classification of petroleum products. The method consists of: chemical analysis; data clean-up by baseline removal, retention time alignment and normalisation; recognition of oil type by classification followed by initial source characterisation. A classification model based on principal components and quadratic discrimination robust towards the effect of short-term weathering was established. The method was tested successfully on real spill and source samples.
Source:Journal of Chromatography A, Volume 1238
N.J. Nielsen, D. Ballabio, G. Tomasi, R. Todeschini, J.H. Christensen
Most oil characterisation procedures are time consuming, labour intensive and utilise only part of the acquired chemical information. Oil spill fingerprinting with multivariate data processing represents a fast and objective evaluation procedure, where the entire chromatographic profile is used. Methods for oil classification should be robust towards changes imposed on the spill fingerprint by short-term weathering, i.e. dissolution and evaporation processes in the hours following a spill. We propose a methodology for the classification of petroleum products. The method consists of: chemical analysis; data clean-up by baseline removal, retention time alignment and normalisation; recognition of oil type by classification followed by initial source characterisation. A classification model based on principal components and quadratic discrimination robust towards the effect of short-term weathering was established. The method was tested successfully on real spill and source samples.
A novel headspace gas chromatographic method for in situ monitoring of monomer conversion during polymerization in an emulsion environment
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Xin-Sheng Chai, Jin-Feng Zhong, Hui-Chao Hu
This paper describes a novel multiple-headspace extraction/gas chromatographic (MHE-GC) technique for monitoring monomer conversion during a polymerization reaction in a water-based emulsion environment. The polymerization reaction of methyl methacrylate (MMA) in an aqueous emulsion is used as an example. The reaction was performed in a closed headspace sample vial (as a mini-reactor), with pentane as a tracer. In situ monitoring of the vapor concentration of the tracer, employing a multiple headspace extraction (sampling) scheme, coupled to a GC, makes it possible to quantitatively follow the conversion of MMA during the early stages of polymerization. Data on the integrated amount of the tracer vapor released from the monomer droplet phase during the polymerization is described by a mathematic equation from which the monomer conversion can be calculated. The present method is simple, automated and economical, and provides an efficient tool in the investigation of the reaction kinetics and effects of the reaction conditions on the early stage of polymerization.
Source:Journal of Chromatography A, Volume 1238
Xin-Sheng Chai, Jin-Feng Zhong, Hui-Chao Hu
This paper describes a novel multiple-headspace extraction/gas chromatographic (MHE-GC) technique for monitoring monomer conversion during a polymerization reaction in a water-based emulsion environment. The polymerization reaction of methyl methacrylate (MMA) in an aqueous emulsion is used as an example. The reaction was performed in a closed headspace sample vial (as a mini-reactor), with pentane as a tracer. In situ monitoring of the vapor concentration of the tracer, employing a multiple headspace extraction (sampling) scheme, coupled to a GC, makes it possible to quantitatively follow the conversion of MMA during the early stages of polymerization. Data on the integrated amount of the tracer vapor released from the monomer droplet phase during the polymerization is described by a mathematic equation from which the monomer conversion can be calculated. The present method is simple, automated and economical, and provides an efficient tool in the investigation of the reaction kinetics and effects of the reaction conditions on the early stage of polymerization.
Use of the isopycnic plots in designing operations of supercritical fluid chromatography: IV. Pressure and density drops along columns
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Abhijit Tarafder, Krzysztof Kaczmarski, Megan Ranger, Donald P. Poe, Georges Guiochon
The pressure- and the density-drops along a chromatographic column eluted with supercritical fluid carbon dioxide were mapped as a function of the outlet column pressure and the temperature on the P–T diagram of neat CO2. At low densities, the viscosity of CO2 is low, which is expected to result into a low pressure drop along the column. However, at these low densities, the volumetric flow rates of the mobile phase at constant mass flow rates are high, which might result into a high pressure drop along the column. These conflicting effects of an adjustment in the mobile phase density on the pressure drop of the mobile phase along the column makes it nearly impossible to develop a simple intuitive understanding of the relationships between the net pressure drops and the operating temperatures and pressures. The development of a similar understanding of their relationships with the density drop along the column is even more complex, because this density drop depends also on the compressibility of the mobile phase, itself a function of the operating pressures and temperatures. Numerical calculations of the pressure and density drops along columns packed with particles of different sizes, under different operating conditions (temperature, outlet pressure, and flow rate), provide important insights regarding the extent of the pressure and density drops under these operating conditions.
Source:Journal of Chromatography A, Volume 1238
Abhijit Tarafder, Krzysztof Kaczmarski, Megan Ranger, Donald P. Poe, Georges Guiochon
The pressure- and the density-drops along a chromatographic column eluted with supercritical fluid carbon dioxide were mapped as a function of the outlet column pressure and the temperature on the P–T diagram of neat CO2. At low densities, the viscosity of CO2 is low, which is expected to result into a low pressure drop along the column. However, at these low densities, the volumetric flow rates of the mobile phase at constant mass flow rates are high, which might result into a high pressure drop along the column. These conflicting effects of an adjustment in the mobile phase density on the pressure drop of the mobile phase along the column makes it nearly impossible to develop a simple intuitive understanding of the relationships between the net pressure drops and the operating temperatures and pressures. The development of a similar understanding of their relationships with the density drop along the column is even more complex, because this density drop depends also on the compressibility of the mobile phase, itself a function of the operating pressures and temperatures. Numerical calculations of the pressure and density drops along columns packed with particles of different sizes, under different operating conditions (temperature, outlet pressure, and flow rate), provide important insights regarding the extent of the pressure and density drops under these operating conditions.
Improved capillary electrophoresis frontal analysis by dynamically coating the capillary with polyelectrolyte multilayers
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Chao Liu, Jingwu Kang
An improved CE-FA method using a polyelectrolyte multilayer (PEML) coated capillary is described. The coating was simply created by alternatively flushing the capillary with positively charged polyelectrolyte polybrene (HDB) and negatively charged polyelectrolyte dextran sulfate (DS). Human serum albumin (HSA) and 6 drugs were selected as an experimental model to evaluate such an improvement. The PEML coating was demonstrated to effectively reduce the protein adsorption on the capillary wall. Compared with the uncoated capillary, the repeatability (RSD%) of the EOF mobility and the plateau height of free drug were improved significantly from 3.7% to 0.51% and from 0.61% to 0.34%, respectively. No interference of the coating on the measurement of protein–drug binding parameters was observed.
Source:Journal of Chromatography A, Volume 1238
Chao Liu, Jingwu Kang
An improved CE-FA method using a polyelectrolyte multilayer (PEML) coated capillary is described. The coating was simply created by alternatively flushing the capillary with positively charged polyelectrolyte polybrene (HDB) and negatively charged polyelectrolyte dextran sulfate (DS). Human serum albumin (HSA) and 6 drugs were selected as an experimental model to evaluate such an improvement. The PEML coating was demonstrated to effectively reduce the protein adsorption on the capillary wall. Compared with the uncoated capillary, the repeatability (RSD%) of the EOF mobility and the plateau height of free drug were improved significantly from 3.7% to 0.51% and from 0.61% to 0.34%, respectively. No interference of the coating on the measurement of protein–drug binding parameters was observed.
High resolution separation by pressure-driven liquid chromatography in meander extended nanochannels
01 May 2012,
09:31:29
Publication year:
2012
Source:Journal of Chromatography A, Volume 1238
Ryo Ishibashi, Kazuma Mawatari, Takehiko Kitamori
The rapidly developing interest in nanofluidics, which is used to examine liquids on an order that ranges from an attoliter to a femtoliter, correlates with the recent interest in decreased sample amounts, such as in the field of single-cell analysis. In this paper, we have succeeded in the normal phase separation of a 101 fL sample with a high number of theoretical plates (103 plates), and a fast separation (4s), using a pressure-driven flow in extended nanochannels. A meander separation channel 1μm wide was introduced and showed no band broadening at the turns, unlike microchannels (101–102 μm wide), which is an important aspect in order to lengthen the channel in a space-limited micro/nanofluidic chip. Our device enables the fast separation of an ultra-small volume of sample with a high number of theoretical plates, and will serve as a general platform for the separation of aL to fL volumes of samples.
Source:Journal of Chromatography A, Volume 1238
Ryo Ishibashi, Kazuma Mawatari, Takehiko Kitamori
The rapidly developing interest in nanofluidics, which is used to examine liquids on an order that ranges from an attoliter to a femtoliter, correlates with the recent interest in decreased sample amounts, such as in the field of single-cell analysis. In this paper, we have succeeded in the normal phase separation of a 101 fL sample with a high number of theoretical plates (103 plates), and a fast separation (4s), using a pressure-driven flow in extended nanochannels. A meander separation channel 1μm wide was introduced and showed no band broadening at the turns, unlike microchannels (101–102 μm wide), which is an important aspect in order to lengthen the channel in a space-limited micro/nanofluidic chip. Our device enables the fast separation of an ultra-small volume of sample with a high number of theoretical plates, and will serve as a general platform for the separation of aL to fL volumes of samples.
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