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:
Capture chromatography for Mo-99 recovery from uranyl sulfate solutions: Minimum-column-volume design method
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Lei Ling , Pei-Lun Chung , Amanda Youker , Dominique C. Stepinski , George F. Vandegrift , Nien-Hwa Linda Wang
Molybdenum-99 (Mo-99), generated from the fission of Uranium-235 (U-235), is the radioactive parent of the most widely used medical isotope, technetium-99m (Tc-99m). An efficient, robust, low-pressure process is developed for recovering Mo-99 from uranyl sulfate solutions. The minimum column volume and the maximum column length for required yield, pressure limit, and loading time are determined using a new graphical method. The method is based on dimensionless groups and intrinsic adsorption and diffusion parameters, which are estimated using a small number of experiments and simulations. The design is tested with bench-scale experiments with titania columns. The results show a high capture yield and a high stripping yield (95±5%). The design can be adapted to changes in design constraints or the variations in feed concentration, feed volume, or material properties. The graph shows clearly how the column utilization is affected by the required yield, loading time, and pressure limit. The cost effectiveness of various sorbent candidates can be evaluated based on the intrinsic parameters. This method can be used more generally for designing other capture chromatography processes.
Source:Journal of Chromatography A, Volume 1309
Author(s): Lei Ling , Pei-Lun Chung , Amanda Youker , Dominique C. Stepinski , George F. Vandegrift , Nien-Hwa Linda Wang
Molybdenum-99 (Mo-99), generated from the fission of Uranium-235 (U-235), is the radioactive parent of the most widely used medical isotope, technetium-99m (Tc-99m). An efficient, robust, low-pressure process is developed for recovering Mo-99 from uranyl sulfate solutions. The minimum column volume and the maximum column length for required yield, pressure limit, and loading time are determined using a new graphical method. The method is based on dimensionless groups and intrinsic adsorption and diffusion parameters, which are estimated using a small number of experiments and simulations. The design is tested with bench-scale experiments with titania columns. The results show a high capture yield and a high stripping yield (95±5%). The design can be adapted to changes in design constraints or the variations in feed concentration, feed volume, or material properties. The graph shows clearly how the column utilization is affected by the required yield, loading time, and pressure limit. The cost effectiveness of various sorbent candidates can be evaluated based on the intrinsic parameters. This method can be used more generally for designing other capture chromatography processes.
Determination of cocaine in postmortem human liver exposed to overdose. Application of an innovative and efficient extraction/clean up procedure and gas chromatography–mass spectrometry analysis
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Elisângela Jaqueline Magalhães , Maria Eliana Lopes Ribeiro de Queiroz , Marcus Luiz de Oliveira Penido , Marco Antônio Ribeiro Paiva , Janaína Aparecida Reis Teodoro , Rodinei Augusti , Clésia Cristina Nascentes
A simple and efficient method was developed for the determination of cocaine in post-mortem samples of human liver via solid–liquid extraction with low temperature partitioning (SLE–LTP) and analysis by gas chromatography coupled to mass spectrometry (GC–MS). The extraction procedure was optimized by evaluating the influence of the following variables: pH of the extract, volume and composition of the extractor solvent, addition of a sorbent material (PSA: primary–secondary amine) and NaCl to clean up and increase the ionic strength of the extract. A bovine liver sample that was free of cocaine was used as a blank for the optimization of the SLE–LTP extraction procedure. The highest recovery was obtained when crushed bovine liver (2g) was treated with 2mL of ultrapure water plus 8mL of acetonitrile at physiological pH (7.4). The results also indicated no need for using PSA and NaCl. The complete analytical procedure was validated for the following figures of merit: selectivity, lower limit of quantification (LLOQ), calibration curve, recovery, precision and accuracy (for within-run and between-run experiments), matrix effect, dilution integrity and stability. The within-run and between-run precision (at four levels) varied from 2.1% to 9.4% and from 4.0% to 17.0%, respectively. A maximum deviation of 11.62% for the within-run and between-run accuracies in relation to the nominal concentrations was observed. Moreover, the LLOQ value for cocaine was 50.0ngg−1 whereas no significant effects were noticed in the assays of dilution integrity and stability. To assess its overall performance, the optimized method was applied to the analysis of eight human liver samples collected from individuals who died due to the abusive consumption of cocaine. Due to the existence of a significant matrix effect, a blank human liver was used to construct a matrix-matched analytical curve. The concentrations of cocaine found in these samples ranged from 333.5 to 5969ngg−1.
Source:Journal of Chromatography A, Volume 1309
Author(s): Elisângela Jaqueline Magalhães , Maria Eliana Lopes Ribeiro de Queiroz , Marcus Luiz de Oliveira Penido , Marco Antônio Ribeiro Paiva , Janaína Aparecida Reis Teodoro , Rodinei Augusti , Clésia Cristina Nascentes
A simple and efficient method was developed for the determination of cocaine in post-mortem samples of human liver via solid–liquid extraction with low temperature partitioning (SLE–LTP) and analysis by gas chromatography coupled to mass spectrometry (GC–MS). The extraction procedure was optimized by evaluating the influence of the following variables: pH of the extract, volume and composition of the extractor solvent, addition of a sorbent material (PSA: primary–secondary amine) and NaCl to clean up and increase the ionic strength of the extract. A bovine liver sample that was free of cocaine was used as a blank for the optimization of the SLE–LTP extraction procedure. The highest recovery was obtained when crushed bovine liver (2g) was treated with 2mL of ultrapure water plus 8mL of acetonitrile at physiological pH (7.4). The results also indicated no need for using PSA and NaCl. The complete analytical procedure was validated for the following figures of merit: selectivity, lower limit of quantification (LLOQ), calibration curve, recovery, precision and accuracy (for within-run and between-run experiments), matrix effect, dilution integrity and stability. The within-run and between-run precision (at four levels) varied from 2.1% to 9.4% and from 4.0% to 17.0%, respectively. A maximum deviation of 11.62% for the within-run and between-run accuracies in relation to the nominal concentrations was observed. Moreover, the LLOQ value for cocaine was 50.0ngg−1 whereas no significant effects were noticed in the assays of dilution integrity and stability. To assess its overall performance, the optimized method was applied to the analysis of eight human liver samples collected from individuals who died due to the abusive consumption of cocaine. Due to the existence of a significant matrix effect, a blank human liver was used to construct a matrix-matched analytical curve. The concentrations of cocaine found in these samples ranged from 333.5 to 5969ngg−1.
Efficient tandem solid-phase extraction and liquid chromatography-triple quadrupole mass spectrometry method to determine polar benzotriazole, benzothiazole and benzenesulfonamide contaminants in environmental water samples
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): P. Herrero , F. Borrull , E. Pocurull , R.M. Marcé
An analytical method has been developed that allows the simultaneous determination of five benzotriazole (BTRs), four benzothiazole (BTs) and five benzenesulfonamide (BSAs) derivates. The method is based on tandem solid-phase extraction (SPE) with Oasis HLB followed by a clean-up step with Florisil. The chromatographic analysis was performed in less than 15min and detection was carried out with a triple quadrupole mass analyser operating in multiple reaction monitoring (MRM) mode. A comparison was performed between Oasis HLB and Oasis MAX sorbents for the solid-phase extraction, with Oasis HLB being the sorbent that gave the highest recoveries, ranging between 75% and 106%, depending on the compound and the matrix analysed. The proposed clean-up with Florisil sorbent reduced the matrix effect to below 20%. The repeatability (%RSD, 50–3000ng/L, n =3) of the method was less than 15% for all of the compounds in all of the matrices. The limits of detection (LODs) achieved ranged from 1ng/L for BTR in river water up to 100ng/L for BT in influent sewage. All of the compounds were determined in environmental waters such as river water and sewage. The highest concentrations determined corresponded to influent sewage samples in which the sum of concentrations for all compounds were between 4.6μg/L and 8.0μg/L. These concentrations were slightly reduced in secondary effluent and tertiary effluent sewage. Moreover, samples from tertiary effluent sewage based on ultra-filtration membrane treatments were also analysed and preliminary results seem to indicate that these treatments may be most effective for removing BTR, BT and BSA derivates.
Source:Journal of Chromatography A, Volume 1309
Author(s): P. Herrero , F. Borrull , E. Pocurull , R.M. Marcé
An analytical method has been developed that allows the simultaneous determination of five benzotriazole (BTRs), four benzothiazole (BTs) and five benzenesulfonamide (BSAs) derivates. The method is based on tandem solid-phase extraction (SPE) with Oasis HLB followed by a clean-up step with Florisil. The chromatographic analysis was performed in less than 15min and detection was carried out with a triple quadrupole mass analyser operating in multiple reaction monitoring (MRM) mode. A comparison was performed between Oasis HLB and Oasis MAX sorbents for the solid-phase extraction, with Oasis HLB being the sorbent that gave the highest recoveries, ranging between 75% and 106%, depending on the compound and the matrix analysed. The proposed clean-up with Florisil sorbent reduced the matrix effect to below 20%. The repeatability (%RSD, 50–3000ng/L, n =3) of the method was less than 15% for all of the compounds in all of the matrices. The limits of detection (LODs) achieved ranged from 1ng/L for BTR in river water up to 100ng/L for BT in influent sewage. All of the compounds were determined in environmental waters such as river water and sewage. The highest concentrations determined corresponded to influent sewage samples in which the sum of concentrations for all compounds were between 4.6μg/L and 8.0μg/L. These concentrations were slightly reduced in secondary effluent and tertiary effluent sewage. Moreover, samples from tertiary effluent sewage based on ultra-filtration membrane treatments were also analysed and preliminary results seem to indicate that these treatments may be most effective for removing BTR, BT and BSA derivates.
Ultrasound-assisted enzymatic hydrolysis for iodinated amino acid extraction from edible seaweed before reversed-phase high performance liquid chromatography–inductively coupled plasma-mass spectrometry
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Vanessa Romarís-Hortas , Pilar Bermejo-Barrera , Antonio Moreda-Piñeiro
The combination of reverse phase high performance liquid chromatography (RP-HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) was used for the determination of monoiodotyrosine (MIT) and diiodotyrosine (DIT) in edible seaweed. A sample pre-treatment based on ultrasound assisted enzymatic hydrolysis was optimized for the extraction of these iodinated amino acids. Pancreatin was selected as the most adequate type of enzyme, and parameters affecting the extraction efficiency (pH, temperature, mass of enzyme and extraction time) were evaluated by univariate approaches. In addition, extractable inorganic iodine (iodide) was also quantified by anion exchange high performance liquid chromatography (AE-HPLC) coupled with ICP-MS. The proposed procedure offered limits of detection of 1.1 and 4.3ngg−1 for MIT and DIT, respectively. Total iodine contents in seaweed, as well as total iodine in enzymatic digests were measured by ICP-MS after microwave assisted alkaline digestion with tetramethylamonium hydroxide (TMAH) for total iodine assessment, and also by treating the pancreatin extracts (extractable total iodine assessment). The optimized procedure was successfully applied to five different types of edible seaweed. The highest total iodine content, and also the highest iodide levels, was found in the brown seaweed Kombu (6646±45μgg−1). Regarding iodinated amino acids, Nori (a red seaweed) was by far the one with the highest amount of both species (42±3 and 0.41±0.024μgg−1 for MIT and DIT, respectively). In general, MIT concentrations were much higher than the amounts of DIT, which suggests that iodine from iodinated proteins in seaweed is most likely bound in the form of MIT residues.
Source:Journal of Chromatography A, Volume 1309
Author(s): Vanessa Romarís-Hortas , Pilar Bermejo-Barrera , Antonio Moreda-Piñeiro
The combination of reverse phase high performance liquid chromatography (RP-HPLC) with inductively coupled plasma mass spectrometry (ICP-MS) was used for the determination of monoiodotyrosine (MIT) and diiodotyrosine (DIT) in edible seaweed. A sample pre-treatment based on ultrasound assisted enzymatic hydrolysis was optimized for the extraction of these iodinated amino acids. Pancreatin was selected as the most adequate type of enzyme, and parameters affecting the extraction efficiency (pH, temperature, mass of enzyme and extraction time) were evaluated by univariate approaches. In addition, extractable inorganic iodine (iodide) was also quantified by anion exchange high performance liquid chromatography (AE-HPLC) coupled with ICP-MS. The proposed procedure offered limits of detection of 1.1 and 4.3ngg−1 for MIT and DIT, respectively. Total iodine contents in seaweed, as well as total iodine in enzymatic digests were measured by ICP-MS after microwave assisted alkaline digestion with tetramethylamonium hydroxide (TMAH) for total iodine assessment, and also by treating the pancreatin extracts (extractable total iodine assessment). The optimized procedure was successfully applied to five different types of edible seaweed. The highest total iodine content, and also the highest iodide levels, was found in the brown seaweed Kombu (6646±45μgg−1). Regarding iodinated amino acids, Nori (a red seaweed) was by far the one with the highest amount of both species (42±3 and 0.41±0.024μgg−1 for MIT and DIT, respectively). In general, MIT concentrations were much higher than the amounts of DIT, which suggests that iodine from iodinated proteins in seaweed is most likely bound in the form of MIT residues.
Effects of the back pressure and the temperature on the finite layer thickness of the adsorbed phase layer in supercritical fluid chromatography
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Péter Vajda , Georges Guiochon
The excess adsorption isotherm of ethanol from liquid carbon dioxide on a silicagel column was determined in a range of back pressures and temperatures. The retention patterns of minor disturbance peaks were mapped and their dependences on the applied back pressure and column temperature measured. The analysis of the linear decreasing part of the excess isotherm around its inflection point provided the finite layer thickness of the adsorbed phase. Our results show that increasing the temperature and decreasing the back pressure result in a thicker layer of the layer of enriched organic solvent above the silicagel surface.
Source:Journal of Chromatography A, Volume 1309
Author(s): Péter Vajda , Georges Guiochon
The excess adsorption isotherm of ethanol from liquid carbon dioxide on a silicagel column was determined in a range of back pressures and temperatures. The retention patterns of minor disturbance peaks were mapped and their dependences on the applied back pressure and column temperature measured. The analysis of the linear decreasing part of the excess isotherm around its inflection point provided the finite layer thickness of the adsorbed phase. Our results show that increasing the temperature and decreasing the back pressure result in a thicker layer of the layer of enriched organic solvent above the silicagel surface.
Determination of selected perfluorinated alkyl acids and persistent organic pollutants from a small volume human serum sample relevant for epidemiological studies
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Jani Koponen , Panu Rantakokko , Riikka Airaksinen , Hannu Kiviranta
A simple and fast method is presented for the determination of selected persistent organic pollutants (POPs) and perfluorinated alkyl acids (PFAAs), a subgroup of per- and polyfluorinated alkyl substances (PFAS) from a single 200μl aliquot of serum. Sample pretreatment starts with dispersive solid phase extraction of POPs to dichloromethane–hexane, which is immediately poured to cleanup column. POPs are eluted from column and concentrated for GC–MS/MS analysis. PFAAs are trapped to dispersant and are then extracted with ammonium acetate in methanol, concentrated and analysed with LC–MS/MS. For POPs, the limit of detection (LOD) ranged from 1.6 to 17pg/ml. Oxychlordane and dichlorodiphenyltrichloroethane had LODs in the upper end of this range as they were more labile and prone for interferences in the GC–MS/MS. For PFAAs, the LOD range from 0.027 to 0.068ng/ml. For POPs, the accuracy from Standard Reference Materials SRM 1589a and Arctic Monitoring and Assessment Programme (AMAP) intercalibration samples range from 74 to 127% and the repeatability (relative standard deviation, RSD%) from 2.0 to 15%. For PFAAs, the accuracy from AMAP samples ranged from 90 to 110% and from LOQ level spiked serum samples from 72 to 133%. Repeatability from AMAP and LOQ samples ranged from 1.6 to 7.3% and 5.5 to 15%, respectively. The presented method is useful in epidemiological studies where only limited amount of serum is available.
Source:Journal of Chromatography A, Volume 1309
Author(s): Jani Koponen , Panu Rantakokko , Riikka Airaksinen , Hannu Kiviranta
A simple and fast method is presented for the determination of selected persistent organic pollutants (POPs) and perfluorinated alkyl acids (PFAAs), a subgroup of per- and polyfluorinated alkyl substances (PFAS) from a single 200μl aliquot of serum. Sample pretreatment starts with dispersive solid phase extraction of POPs to dichloromethane–hexane, which is immediately poured to cleanup column. POPs are eluted from column and concentrated for GC–MS/MS analysis. PFAAs are trapped to dispersant and are then extracted with ammonium acetate in methanol, concentrated and analysed with LC–MS/MS. For POPs, the limit of detection (LOD) ranged from 1.6 to 17pg/ml. Oxychlordane and dichlorodiphenyltrichloroethane had LODs in the upper end of this range as they were more labile and prone for interferences in the GC–MS/MS. For PFAAs, the LOD range from 0.027 to 0.068ng/ml. For POPs, the accuracy from Standard Reference Materials SRM 1589a and Arctic Monitoring and Assessment Programme (AMAP) intercalibration samples range from 74 to 127% and the repeatability (relative standard deviation, RSD%) from 2.0 to 15%. For PFAAs, the accuracy from AMAP samples ranged from 90 to 110% and from LOQ level spiked serum samples from 72 to 133%. Repeatability from AMAP and LOQ samples ranged from 1.6 to 7.3% and 5.5 to 15%, respectively. The presented method is useful in epidemiological studies where only limited amount of serum is available.
Properties of columns with several pyridinium and imidazolium ionic liquid stationary phases
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): M.V. Shashkov , V.N. Sidelnikov
Recent advances in the development of new liquid phases (ILs) made it possible to use some classes of ILs as polar stationary liquid phases (SLP). In our days only alkylimidazolium- and alkylphosphonium-based ILs are widely used as polar SLP. In present work some other types of ILs – pyridinium and cyanopropyl/hydroxypropyl imidazolium were investigated as SLP. Columns with efficiencies 2000–2500 plates/m by high-pressure static method were prepared. Polarity and selectivity of these phases were measured. Selectivity was described in terms of intermolecular interactions by using Abraham solvatation parameter model. The set of the regularities between cation structure of ionic liquid and selectivity has been shown. The number and position of methyl groups in ionic liquid pyridinium ring were shown to have the sufficient influence on all type of molecular interactions. Finally the resolutions of test mixture for the several ionic liquid SLP were obtained. For columns with some ionic liquids the dependencies of the height equivalent to a theoretical plate (HETP) and sample loading capacity were obtained and compared with the conventional phases. It was found that the optimal efficiency for the IL columns is attained at lower carrier gas velocities in comparison with traditional phases. Nevetheless sample loading capacity of IL phases is comparable to those of conventional GC phases.
Source:Journal of Chromatography A, Volume 1309
Author(s): M.V. Shashkov , V.N. Sidelnikov
Recent advances in the development of new liquid phases (ILs) made it possible to use some classes of ILs as polar stationary liquid phases (SLP). In our days only alkylimidazolium- and alkylphosphonium-based ILs are widely used as polar SLP. In present work some other types of ILs – pyridinium and cyanopropyl/hydroxypropyl imidazolium were investigated as SLP. Columns with efficiencies 2000–2500 plates/m by high-pressure static method were prepared. Polarity and selectivity of these phases were measured. Selectivity was described in terms of intermolecular interactions by using Abraham solvatation parameter model. The set of the regularities between cation structure of ionic liquid and selectivity has been shown. The number and position of methyl groups in ionic liquid pyridinium ring were shown to have the sufficient influence on all type of molecular interactions. Finally the resolutions of test mixture for the several ionic liquid SLP were obtained. For columns with some ionic liquids the dependencies of the height equivalent to a theoretical plate (HETP) and sample loading capacity were obtained and compared with the conventional phases. It was found that the optimal efficiency for the IL columns is attained at lower carrier gas velocities in comparison with traditional phases. Nevetheless sample loading capacity of IL phases is comparable to those of conventional GC phases.
Robust analysis of the hydrophobic basic analytes loratadine and desloratadine in pharmaceutical preparations and biological fluids by sweeping—cyclodextrin-modified micellar electrokinetic chromatography
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Mohamed El-Awady , Fathalla Belal , Ute Pyell
The analysis of hydrophobic basic analytes by micellar electrokinetic chromatography (MEKC) is usually challenging because of the tendency of these analytes to be adsorbed onto the inner capillary wall in addition to the difficulty to separate these compounds as they exhibit extremely high retention factors. A robust and reliable method for the simultaneous determination of loratadine (LOR) and its major metabolite desloratadine (DSL) is developed based on cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with acidic sample matrix and basic background electrolyte (BGE). The influence of the sample matrix on the reachable focusing efficiency is studied. It is shown that the application of a low pH sample solution mitigates problems associated with the low solubility of the hydrophobic basic analytes in aqueous solution while having advantages with regard to on-line focusing. Moreover, the use of a basic BGE reduces the adsorption of these analytes in the separation compartment. The separation of the studied analytes is achieved in less than 7min using a BGE consisting of 10mmolL−1 disodium tetraborate buffer, pH 9.30 containing 40mmolL−1 SDS and 20mmolL−1 hydroxypropyl-β-CD while the sample solution is composed of 10mmolL−1 phosphoric acid, pH 2.15. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in tablets without interference of tablet additives as well as the analysis of spiked human urine without any sample pretreatment. Furthermore, DSL can be detected as an impurity in LOR bulk powder at the stated pharmacopeial limit (0.1%, w/w). The selectivity of the developed method allows the analysis of LOR and DSL in combination with the co-formulated drug pseudoephedrine. It is shown that in CD-MEKC with basic BGE, solute–wall interactions are effectively suppressed allowing the development of efficient and precise methods for the determination of hydrophobic basic analytes, whereas the use of a low pH sample solution has a positive impact on the attainable sweeping efficiency without compromising peak shape and resolution.
Source:Journal of Chromatography A, Volume 1309
Author(s): Mohamed El-Awady , Fathalla Belal , Ute Pyell
The analysis of hydrophobic basic analytes by micellar electrokinetic chromatography (MEKC) is usually challenging because of the tendency of these analytes to be adsorbed onto the inner capillary wall in addition to the difficulty to separate these compounds as they exhibit extremely high retention factors. A robust and reliable method for the simultaneous determination of loratadine (LOR) and its major metabolite desloratadine (DSL) is developed based on cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with acidic sample matrix and basic background electrolyte (BGE). The influence of the sample matrix on the reachable focusing efficiency is studied. It is shown that the application of a low pH sample solution mitigates problems associated with the low solubility of the hydrophobic basic analytes in aqueous solution while having advantages with regard to on-line focusing. Moreover, the use of a basic BGE reduces the adsorption of these analytes in the separation compartment. The separation of the studied analytes is achieved in less than 7min using a BGE consisting of 10mmolL−1 disodium tetraborate buffer, pH 9.30 containing 40mmolL−1 SDS and 20mmolL−1 hydroxypropyl-β-CD while the sample solution is composed of 10mmolL−1 phosphoric acid, pH 2.15. A full validation study of the developed method based on the pharmacopeial guidelines is performed. The method is successfully applied to the analysis of the studied drugs in tablets without interference of tablet additives as well as the analysis of spiked human urine without any sample pretreatment. Furthermore, DSL can be detected as an impurity in LOR bulk powder at the stated pharmacopeial limit (0.1%, w/w). The selectivity of the developed method allows the analysis of LOR and DSL in combination with the co-formulated drug pseudoephedrine. It is shown that in CD-MEKC with basic BGE, solute–wall interactions are effectively suppressed allowing the development of efficient and precise methods for the determination of hydrophobic basic analytes, whereas the use of a low pH sample solution has a positive impact on the attainable sweeping efficiency without compromising peak shape and resolution.
Quality assurance of monoclonal antibody pharmaceuticals based on their charge variants using microchip isoelectric focusing method
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Mitsuhiro Kinoshita , Yuki Nakatsuji , Shigeo Suzuki , Takao Hayakawa , Kazuaki Kakehi
Monoclonal antibody (mAb) pharmaceuticals are much more complex than small-molecule drugs. Such complex characteristics raise challenging questions for regulatory evaluation. Although heterogeneity in mAbs based on their charge variants has been mainly evaluated using gel-based isoelectric focusing (IEF) method, recent development in capillary electrophoresis and microchip electrophoresis has made it possible to assure their heterogeneities in more easy and rapid manner. In the present paper, we customized the imaged microchip isoelectric focusing (mIEF) for the analysis of mAbs, and compared the customized version with the conventional capillary isoelectric focusing (cIEF) method, and found that mIEF has much higher performance in operations, and its resolving powers are comparable with those obtained by cIEF.
Source:Journal of Chromatography A, Volume 1309
Author(s): Mitsuhiro Kinoshita , Yuki Nakatsuji , Shigeo Suzuki , Takao Hayakawa , Kazuaki Kakehi
Monoclonal antibody (mAb) pharmaceuticals are much more complex than small-molecule drugs. Such complex characteristics raise challenging questions for regulatory evaluation. Although heterogeneity in mAbs based on their charge variants has been mainly evaluated using gel-based isoelectric focusing (IEF) method, recent development in capillary electrophoresis and microchip electrophoresis has made it possible to assure their heterogeneities in more easy and rapid manner. In the present paper, we customized the imaged microchip isoelectric focusing (mIEF) for the analysis of mAbs, and compared the customized version with the conventional capillary isoelectric focusing (cIEF) method, and found that mIEF has much higher performance in operations, and its resolving powers are comparable with those obtained by cIEF.
Liquid crystal-based molecularly imprinted nanoparticles with low crosslinking for capillary electrochromatography
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Xiao Liu , Hai-Yan Zong , Yan-Ping Huang , Zhao-Sheng Liu
In this work, molecularly imprinted polymer (MIP) nanoparticles were prepared at a low level of crosslinking in the presence of liquid crystalline monomer as physical crosslinker to replace the most of chemical crosslinker. The imprinted nanoparticles against d-zopiclone were synthesized by precipitation polymerization using a mixture of methacrylic acid, ethylene glycol dimethacrylate, and liquid crystalline monomers. The resulting d-zopiclone imprinted nanoparticles were evaluated in capillary electrochromatography by partial filling technique. The resolution of enantiomer separation achieved on the d-zopiclone-imprinted nanoparticles was up to 3.29 and the column efficiency of zopiclone enantiomer (up to 66,900 plates/m) with good peak symmetry was obtained. The imprinted nanoparticles prepared in the presence of liquid crystalline monomer can retain affinity and specificity for template even when prepared with a level of cross-linker as low as 5%.
Source:Journal of Chromatography A, Volume 1309
Author(s): Xiao Liu , Hai-Yan Zong , Yan-Ping Huang , Zhao-Sheng Liu
In this work, molecularly imprinted polymer (MIP) nanoparticles were prepared at a low level of crosslinking in the presence of liquid crystalline monomer as physical crosslinker to replace the most of chemical crosslinker. The imprinted nanoparticles against d-zopiclone were synthesized by precipitation polymerization using a mixture of methacrylic acid, ethylene glycol dimethacrylate, and liquid crystalline monomers. The resulting d-zopiclone imprinted nanoparticles were evaluated in capillary electrochromatography by partial filling technique. The resolution of enantiomer separation achieved on the d-zopiclone-imprinted nanoparticles was up to 3.29 and the column efficiency of zopiclone enantiomer (up to 66,900 plates/m) with good peak symmetry was obtained. The imprinted nanoparticles prepared in the presence of liquid crystalline monomer can retain affinity and specificity for template even when prepared with a level of cross-linker as low as 5%.
Sequential determination of new peptaibols asperelines G-Z12 produced by marine-derived fungus Trichoderma asperellum using ultrahigh pressure liquid chromatography combined with electrospray-ionization tandem mass spectrometry
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Jinwei Ren , Yi Yang , Dong Liu , Wei Chen , Peter Proksch , Bing Shao , Wenhan Lin
Thirty-eight short peptaibols in a microheterogeneous mixture derived from the fermentation broth of a marine-derived fungus Trichoderma asperellum were determined using ultrahigh pressure liquid chromatography in combination with electrospray-ionization tandem mass spectrometry (UHPLC–ESIMS/MS) techniques, including thirty-two new peptaibols namely asperelines G-Z13. The C-terminus bonded to proline (aspereline Z9) or hydroxyprolinol (aspereline Z12) is rarely found in nature. So far, it is the largest number of peptaibols to be detected at once on the basis of the selected ion monitoring (SIM) mode coupled to precursor scan techniques.
Source:Journal of Chromatography A, Volume 1309
Author(s): Jinwei Ren , Yi Yang , Dong Liu , Wei Chen , Peter Proksch , Bing Shao , Wenhan Lin
Thirty-eight short peptaibols in a microheterogeneous mixture derived from the fermentation broth of a marine-derived fungus Trichoderma asperellum were determined using ultrahigh pressure liquid chromatography in combination with electrospray-ionization tandem mass spectrometry (UHPLC–ESIMS/MS) techniques, including thirty-two new peptaibols namely asperelines G-Z13. The C-terminus bonded to proline (aspereline Z9) or hydroxyprolinol (aspereline Z12) is rarely found in nature. So far, it is the largest number of peptaibols to be detected at once on the basis of the selected ion monitoring (SIM) mode coupled to precursor scan techniques.
Determination of the column hold-up volume in supercritical fluid chromatography using nitrous-oxide
04 September 2013,
09:16:02
Publication date: 27 September
2013
Source:Journal of Chromatography A, Volume 1309
Author(s): Péter Vajda , Georges Guiochon
This study introduces a new tracer that is useful for the determination of the hold-up time or volume of packed columns, particularly of those used in supercritical fluid chromatography. The thermodynamic void volume of three columns packed with different adsorbents were determined using the weight difference method. These void volumes were used as the reference point in the further discussion. The hold-up volumes of these columns were determined under dynamic conditions, using nitrous oxide dissolved in methanol as the hold-up time marker. Changes in the hold-up volumes of these columns were monitored during changes of the volumetric flow rate of pure supercritical carbon dioxide and of dilute mixtures of organic modifier and supercritical carbon dioxide. The results suggest significant methanol enrichment on the adsorbent surface.
Source:Journal of Chromatography A, Volume 1309
Author(s): Péter Vajda , Georges Guiochon
This study introduces a new tracer that is useful for the determination of the hold-up time or volume of packed columns, particularly of those used in supercritical fluid chromatography. The thermodynamic void volume of three columns packed with different adsorbents were determined using the weight difference method. These void volumes were used as the reference point in the further discussion. The hold-up volumes of these columns were determined under dynamic conditions, using nitrous oxide dissolved in methanol as the hold-up time marker. Changes in the hold-up volumes of these columns were monitored during changes of the volumetric flow rate of pure supercritical carbon dioxide and of dilute mixtures of organic modifier and supercritical carbon dioxide. The results suggest significant methanol enrichment on the adsorbent surface.
No comments:
Post a Comment