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Selected papers from the latest issue:
Analysis of bisphenol A and its chlorinated derivatives in sewage sludge samples. Comparison of the efficiency of three extraction techniques
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
N. Dorival-García, A. Zafra-Gómez, A. Navalón, J.L. Vílchez
This paper presents a comparison of three extraction techniques—ultrasound-assisted extraction, microwave-assisted extraction and pressurized liquid extraction—in order to evaluate their efficiency in the determination of bisphenol A and its chlorinated derivatives in sewage sludge samples. Extraction parameters for each technique were accurately optimized to achieve the highest recoveries. The selected compounds were detected and quantified using liquid chromatography–tandem mass spectrometry (LC–MS/MS), operating in negative atmospheric pressure chemical ionization (APCI) and in multiple reaction monitoring (MRM) mode. The analytes were separated in less than 6min. BPA-d16 was used as internal standard. Three selective, sensitive, robust and accurate analytical methods were developed. The limits of detection (LODs) of the methods ranged from 2 to 9ngg−1 and the limits of quantification (LOQs) from 8 to 26ngg−1, while inter- and intra-day variability was under 6% in all cases. Given the absence of certified reference materials (CRMs), the methods were validated separately by using matrix-matched calibration and recovery assays with spiked samples. Recovery rates ranged from 97.7% to 103.1%. The sewage sludge samples used for experiments were collected from two different wastewater treatments plants (WWTPs) located in the province of Granada (South-East Spain). The statistical comparison of the methods demonstrated no statistically significant differences between the extraction techniques for the determination of BPA and chlorinated derivatives in sludge samples.
Source:Journal of Chromatography A, Volume 1253
N. Dorival-García, A. Zafra-Gómez, A. Navalón, J.L. Vílchez
This paper presents a comparison of three extraction techniques—ultrasound-assisted extraction, microwave-assisted extraction and pressurized liquid extraction—in order to evaluate their efficiency in the determination of bisphenol A and its chlorinated derivatives in sewage sludge samples. Extraction parameters for each technique were accurately optimized to achieve the highest recoveries. The selected compounds were detected and quantified using liquid chromatography–tandem mass spectrometry (LC–MS/MS), operating in negative atmospheric pressure chemical ionization (APCI) and in multiple reaction monitoring (MRM) mode. The analytes were separated in less than 6min. BPA-d16 was used as internal standard. Three selective, sensitive, robust and accurate analytical methods were developed. The limits of detection (LODs) of the methods ranged from 2 to 9ngg−1 and the limits of quantification (LOQs) from 8 to 26ngg−1, while inter- and intra-day variability was under 6% in all cases. Given the absence of certified reference materials (CRMs), the methods were validated separately by using matrix-matched calibration and recovery assays with spiked samples. Recovery rates ranged from 97.7% to 103.1%. The sewage sludge samples used for experiments were collected from two different wastewater treatments plants (WWTPs) located in the province of Granada (South-East Spain). The statistical comparison of the methods demonstrated no statistically significant differences between the extraction techniques for the determination of BPA and chlorinated derivatives in sludge samples.
Highlights
► Three extraction techniques to isolate BPA from sewage sludge samples are compared. ► The three methods are valid and offer accurate and precise determination of compounds. ► PLE, USE and MAE are accurately optimized prior to LC–MS/MS analysis. ► Validation of the three methods: quality parameters, accuracy (trueness and precision).Pneumatic nebulization gas–solid extraction of some pesticides in liquor
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Yeqiang Wang, Fan Wang, Cui Yu, Na Li, Rui Zhang, Ruibing Ren, Hanqi Zhang
In general, solid phase extraction (SPE) was applied to the separation and concentration of analytes from liquid samples. However, the SPE generally cannot be applied directly to the separation and concentration of analytes from liquor in which the concentration of ethanol is high, because the ethanol can elute the analytes from the SPE column and the analytes can hardly been adsorbed onto the column. In the work, the pneumatic nebulization coupled with gas–solid extraction (PN-GSE) was applied to the extraction of several pesticides, including fenuron, chlortoluron, karmex, linuron and prebane, from liquor samples. The high concentration of ethanol in the liquor samples cannot elute the analytes from the SPE column. The high performance liquid chromatography was applied to the separation and determination of the analytes. Experimental parameters affecting the performances of PN-GSE, such as types and amount of packed material of the column, temperature of the spray chamber, flow rate of carrier gas, pumping rate of gas and volume of elution solvent were examined and optimized. The limits of detection for the analytes were in the range of 0.19–0.26μgL−1. Liquor samples were analyzed and the recoveries of the analytes in spiked samples were from 91.0 to 106.3%. The relative standard deviations were lower than 6.5%.
Source:Journal of Chromatography A, Volume 1253
Yeqiang Wang, Fan Wang, Cui Yu, Na Li, Rui Zhang, Ruibing Ren, Hanqi Zhang
In general, solid phase extraction (SPE) was applied to the separation and concentration of analytes from liquid samples. However, the SPE generally cannot be applied directly to the separation and concentration of analytes from liquor in which the concentration of ethanol is high, because the ethanol can elute the analytes from the SPE column and the analytes can hardly been adsorbed onto the column. In the work, the pneumatic nebulization coupled with gas–solid extraction (PN-GSE) was applied to the extraction of several pesticides, including fenuron, chlortoluron, karmex, linuron and prebane, from liquor samples. The high concentration of ethanol in the liquor samples cannot elute the analytes from the SPE column. The high performance liquid chromatography was applied to the separation and determination of the analytes. Experimental parameters affecting the performances of PN-GSE, such as types and amount of packed material of the column, temperature of the spray chamber, flow rate of carrier gas, pumping rate of gas and volume of elution solvent were examined and optimized. The limits of detection for the analytes were in the range of 0.19–0.26μgL−1. Liquor samples were analyzed and the recoveries of the analytes in spiked samples were from 91.0 to 106.3%. The relative standard deviations were lower than 6.5%.
Highlights
► A novel method, pneumatic nebulization gas–solid extraction (PN-GSE) was developed. ► The high concentration of ethanol in liquor cannot elute the analytes from the SPE column. ► In the PN-GSE, the sampling is very convenient. ► The present method should be suitable for the extraction of trace impurities in liquor.Analysis of phenolic pollutants in human samples by high performance capillary electrophoresis based on pretreatment of ultrasound-assisted emulsification microextraction and solidification of floating organic droplet
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Huili Wang, Hao Yan, Chengjun Wang, Fan Chen, Meiping Ma, Wenwei Wang, Xuedong Wang
A novel, simple and rapid method, termed ultrasound-assisted emulsification microextraction and solidification of floating organic droplet (UAEM–SFO) coupled to high performance capillary electrophoresis (HPCE), was developed for preconcentration and analysis of five phenolic compounds (PCs) in human urine and blood samples. The proposed method is based on microextraction of target analytes in less-toxic organic solvent under assistance of ultrasound. A micro-droplet of less-toxic organic solvent floating on the surface of liquid samples in a sealed vial can be dispersed into sample solutions under the ultrasound frequency, solidified under ice bath, collected with a medicine spatula, molten at ambient temperature, and finally subjected to HPCE analysis. The parameters of UAEM–SFO procedure including type and volume of extraction solvent, extraction temperature, time of ultrasound-assisted extraction and centrifugation, sample pH, and ionic strength were optimized. The influence parameters on HPCE resolution such as pH, concentration of running buffer, applied voltage and injection time were also investigated. This method requires only 40μL of 2-dodecanol extraction solvent and 8min of pretreatment time. The enrichment factors of analytes were in the range of 114–172 and extraction recoveries (69–86%) were obtained. Good linearity was achieved for five analytes in the range of 0.05–100μgL−1 and the correlation coefficients ranged from 0.9934 to 0.9999. The limits of detection were 0.01μgL−1for triclosan (TCS) and biophenol A (BPA), and 0.02μgL−1 for pentachlorophenol (PCP), 2,4-dichlorophenol (2,4-DCP) and 4-nonylphenol (4-NP) in urine samples, and 0.02μgL−1 for TCS and BPA, 0.04μgL−1 for PCP, 2,4-DCP and 4-NP in blood samples. The developed UAEM–SFO–HPCE method has a great potential in routine residual analysis of trace PCs in biological samples.
Source:Journal of Chromatography A, Volume 1253
Huili Wang, Hao Yan, Chengjun Wang, Fan Chen, Meiping Ma, Wenwei Wang, Xuedong Wang
A novel, simple and rapid method, termed ultrasound-assisted emulsification microextraction and solidification of floating organic droplet (UAEM–SFO) coupled to high performance capillary electrophoresis (HPCE), was developed for preconcentration and analysis of five phenolic compounds (PCs) in human urine and blood samples. The proposed method is based on microextraction of target analytes in less-toxic organic solvent under assistance of ultrasound. A micro-droplet of less-toxic organic solvent floating on the surface of liquid samples in a sealed vial can be dispersed into sample solutions under the ultrasound frequency, solidified under ice bath, collected with a medicine spatula, molten at ambient temperature, and finally subjected to HPCE analysis. The parameters of UAEM–SFO procedure including type and volume of extraction solvent, extraction temperature, time of ultrasound-assisted extraction and centrifugation, sample pH, and ionic strength were optimized. The influence parameters on HPCE resolution such as pH, concentration of running buffer, applied voltage and injection time were also investigated. This method requires only 40μL of 2-dodecanol extraction solvent and 8min of pretreatment time. The enrichment factors of analytes were in the range of 114–172 and extraction recoveries (69–86%) were obtained. Good linearity was achieved for five analytes in the range of 0.05–100μgL−1 and the correlation coefficients ranged from 0.9934 to 0.9999. The limits of detection were 0.01μgL−1for triclosan (TCS) and biophenol A (BPA), and 0.02μgL−1 for pentachlorophenol (PCP), 2,4-dichlorophenol (2,4-DCP) and 4-nonylphenol (4-NP) in urine samples, and 0.02μgL−1 for TCS and BPA, 0.04μgL−1 for PCP, 2,4-DCP and 4-NP in blood samples. The developed UAEM–SFO–HPCE method has a great potential in routine residual analysis of trace PCs in biological samples.
Highlights
► The proposed method is UAEM–SFO–HPCE for determination of five phenolic chemicals. ► The enrichment factors for this method are from 114 to 172. ► The extraction recoveries are in the range of 69–86%. ► The limits of detection are 0.01–0.04μgL−1 in human urine or blood samples. ► The limits of detection are approximately 10-fold lower than previously reported methods.Preparation of porous polymer monolithic column incorporated with graphene nanosheets for solid phase microextraction and enrichment of glucocorticoids
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Shanshan Tong, Qingwen Liu, Yanchun Li, Weihong Zhou, Qiong Jia, Taicheng Duan
Novel monolithic capillary columns with embedded graphene were developed and used for polymer monolith microextraction (PMME) coupled to LC–MS analysis. The column was prepared inside fused silica capillaries (320μm, i.d.) using thermally initiated free-radical polymerization with butyl methacrylate (BMA) as monomer, ethylene dimethacrylate (EDMA) as cross-linker, and 1,4-butanediol and 1-propanol as porogens. Graphene (GN) was incorporated into the poly(BMA–EDMA) monolith to enhance the loading capacity. The obtained GN and the poly(BMA–EDMA–GN) monolith were characterized by transmission electron microscope (TEM), atomic force microscopic (AFM) and scanning electron microscopy (SEM). The extraction performance of the monolithic column was evaluated by glucocorticoids (GCs) as the analytes. The operation parameters of PMME including desorption solvent, sample flow rate, sample volume, sample pH, and eluent flow rate were studied and optimized. When compared to the parent poly(BMA–EDMA) column and direct sample analysis, high enrichment capacity was observed in the case of GN-entrapped monolith. The GN incorporated monolithic capillary showed satisfactory reusability and stability during extraction. The limits of detection (S/N=3) for nine GCs were in the range of 0.13–1.93ng/mL. Relative standard deviations for the determination of the target GCs were less than 14.5%. Finally, the PMME method, based on the developed monolithic capillary as the extraction media, was successfully applied to the determination of nine GCs in cosmetics. The recoveries of GCs spiked in different matrices ranged from 83.7% to 103.8%.
Source:Journal of Chromatography A, Volume 1253
Shanshan Tong, Qingwen Liu, Yanchun Li, Weihong Zhou, Qiong Jia, Taicheng Duan
Novel monolithic capillary columns with embedded graphene were developed and used for polymer monolith microextraction (PMME) coupled to LC–MS analysis. The column was prepared inside fused silica capillaries (320μm, i.d.) using thermally initiated free-radical polymerization with butyl methacrylate (BMA) as monomer, ethylene dimethacrylate (EDMA) as cross-linker, and 1,4-butanediol and 1-propanol as porogens. Graphene (GN) was incorporated into the poly(BMA–EDMA) monolith to enhance the loading capacity. The obtained GN and the poly(BMA–EDMA–GN) monolith were characterized by transmission electron microscope (TEM), atomic force microscopic (AFM) and scanning electron microscopy (SEM). The extraction performance of the monolithic column was evaluated by glucocorticoids (GCs) as the analytes. The operation parameters of PMME including desorption solvent, sample flow rate, sample volume, sample pH, and eluent flow rate were studied and optimized. When compared to the parent poly(BMA–EDMA) column and direct sample analysis, high enrichment capacity was observed in the case of GN-entrapped monolith. The GN incorporated monolithic capillary showed satisfactory reusability and stability during extraction. The limits of detection (S/N=3) for nine GCs were in the range of 0.13–1.93ng/mL. Relative standard deviations for the determination of the target GCs were less than 14.5%. Finally, the PMME method, based on the developed monolithic capillary as the extraction media, was successfully applied to the determination of nine GCs in cosmetics. The recoveries of GCs spiked in different matrices ranged from 83.7% to 103.8%.
Highlights
► Poly(BMA–EDMA) monolithic column integrated with graphene nanosheets was prepared. ► The monolithic column was applied to the enrichment of glucocorticoids. ► The monolithic column has high preconcentration abilities for glucocorticoids. ► Good reproducibility of the preparation of monolithic columns was achieved.Simulation model for overloaded monoclonal antibody variants separations in ion-exchange chromatography
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Bertrand Guélat, Guido Ströhlein, Marco Lattuada, Lydia Delegrange, Pascal Valax, Massimo Morbidelli
A model was developed for the design of a monoclonal antibody charge variants separation process based on ion-exchange chromatography. In order to account for a broad range of operating conditions in the simulations, an explicit pH and salt concentration dependence has been included in the Langmuir adsorption isotherm. The reliability of this model was tested using experimental chromatographic retention times as well as information about the structural characteristics of the different charge variants, e.g. C-terminal lysine groups and deamidated groups. Next, overloaded isocratic elutions at various pH and salt concentrations have been performed to determine the saturation capacity of the ion-exchanger. Furthermore, the column simulation model was applied for the prediction of monoclonal antibody variants separations with both pH and salt gradient elutions. A good prediction of the elution times and peak shapes was observed, even though none of the model parameters was adjusted to fit the experimental data. The trends in the separation performance obtained through the simulations were generally sufficient to identify the most promising operating conditions. The predictive column simulation model thus developed in this work, including a set of parameters determined through specific independent experiments, was experimentally validated and offers a useful basis for a rational optimization of monoclonal antibody variants separation processes on ion-exchange chromatography.
Source:Journal of Chromatography A, Volume 1253
Bertrand Guélat, Guido Ströhlein, Marco Lattuada, Lydia Delegrange, Pascal Valax, Massimo Morbidelli
A model was developed for the design of a monoclonal antibody charge variants separation process based on ion-exchange chromatography. In order to account for a broad range of operating conditions in the simulations, an explicit pH and salt concentration dependence has been included in the Langmuir adsorption isotherm. The reliability of this model was tested using experimental chromatographic retention times as well as information about the structural characteristics of the different charge variants, e.g. C-terminal lysine groups and deamidated groups. Next, overloaded isocratic elutions at various pH and salt concentrations have been performed to determine the saturation capacity of the ion-exchanger. Furthermore, the column simulation model was applied for the prediction of monoclonal antibody variants separations with both pH and salt gradient elutions. A good prediction of the elution times and peak shapes was observed, even though none of the model parameters was adjusted to fit the experimental data. The trends in the separation performance obtained through the simulations were generally sufficient to identify the most promising operating conditions. The predictive column simulation model thus developed in this work, including a set of parameters determined through specific independent experiments, was experimentally validated and offers a useful basis for a rational optimization of monoclonal antibody variants separation processes on ion-exchange chromatography.
Highlights
► The adsorption equilibrium of proteins in ion-exchange chromatography was modeled. ► The dependence upon pH and salt concentration was modeled. ► Overloaded salt and pH gradient elutions were predicted. ► The model can be used to optimize the preparative mAb variants separation.Determination of pharmaceutically related compounds by suppressed ion chromatography: IV. Interfacing ion chromatography with universal detectors
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Naama Karu, Joseph P. Hutchinson, Greg W. Dicinoski, Melissa Hanna-Brown, Kannan Srinivasan, Christopher A. Pohl, Paul R. Haddad
This work forms the final part of a study investigating gradient elution ion-exchange chromatography of pharmaceutically relevant compounds, aiming at achieving complementary selectivity to reversed-phase HPLC. In this study the coupling of three universal detectors (electro-spray ionisation mass spectrometer (ESI-MS); corona charged aerosol detector (CAD); and evaporative light scattering detector (ELSD)) to suppressed IC using complex elution profiles with potassium hydroxide eluents is demonstrated. The non-volatile ions were removed from the eluent by the suppressor prior to detection, thus allowing a stable detector response, especially with the prototype electrolytic suppressor. The detector response for ten weakly anionic pharmaceuticals followed the expected models and the limits of detection obtained were not compromised by the use of a suppressor, yielding values below 50ng/mL with MS, low to sub μg/mL levels with CAD and 2–20μg/mL with ELSD (25μL injections). When coupled to MS and CAD, the prototype electrolytic suppressor showed percentage relative standard deviations (%RSDs) in peak areas of 0.4–2.5% on average, compared to the chemical suppressor which yielded 1.5–3 fold higher %RSD values for the test analytes. The prototype electrolytic suppressor also generally exhibited wider linear response ranges than the chemical suppressor.
Source:Journal of Chromatography A, Volume 1253
Naama Karu, Joseph P. Hutchinson, Greg W. Dicinoski, Melissa Hanna-Brown, Kannan Srinivasan, Christopher A. Pohl, Paul R. Haddad
This work forms the final part of a study investigating gradient elution ion-exchange chromatography of pharmaceutically relevant compounds, aiming at achieving complementary selectivity to reversed-phase HPLC. In this study the coupling of three universal detectors (electro-spray ionisation mass spectrometer (ESI-MS); corona charged aerosol detector (CAD); and evaporative light scattering detector (ELSD)) to suppressed IC using complex elution profiles with potassium hydroxide eluents is demonstrated. The non-volatile ions were removed from the eluent by the suppressor prior to detection, thus allowing a stable detector response, especially with the prototype electrolytic suppressor. The detector response for ten weakly anionic pharmaceuticals followed the expected models and the limits of detection obtained were not compromised by the use of a suppressor, yielding values below 50ng/mL with MS, low to sub μg/mL levels with CAD and 2–20μg/mL with ELSD (25μL injections). When coupled to MS and CAD, the prototype electrolytic suppressor showed percentage relative standard deviations (%RSDs) in peak areas of 0.4–2.5% on average, compared to the chemical suppressor which yielded 1.5–3 fold higher %RSD values for the test analytes. The prototype electrolytic suppressor also generally exhibited wider linear response ranges than the chemical suppressor.
Highlights
► Ion-exchange separations are coupled with MS, ELSD and CAD. ► An in-line suppressor is used to de-salt the eluent prior to detection. ► Stable detector baselines were obtained when gradient elution was employed. ► A new high capacity electrolytic suppressor gave optimal performance.Development of a two-dimensional high-performance liquid chromatography system coupled with on-line reduction as a new efficient analytical method of 3-nitrobenzanthrone, a potential human carcinogen
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Tomohiro Hasei, Haruka Nakanishi, Yumiko Toda, Tetsushi Watanabe
3-Nitrobenzanthrone (3-NBA) is an extremely strong mutagen and carcinogen in rats inducing squamous cell carcinoma and adenocarcinoma. We developed a new sensitive analytical method, a two-dimensional HPLC system coupled with on-line reduction, to quantify non-fluorescent 3-NBA as fluorescent 3-aminobenzanthrone (3-ABA). The two-dimensional HPLC system consisted of reversed-phase HPLC and normal-phase HPLC, which were connected with a switch valve. 3-NBA was purified by reversed-phase HPLC and reduced to 3-ABA with a catalyst column, packed with alumina coated with platinum, in ethanol. An alcoholic solvent is necessary for reduction of 3-NBA, but 3-ABA is not fluorescent in the alcoholic solvent. Therefore, 3-ABA was separated from alcohol and impurities by normal-phase HPLC and detected with a fluorescence detector. Extracts from surface soil, airborne particles, classified airborne particles, and incinerator dust were applied to the two-dimensional HPLC system after clean-up with a silica gel column. 3-NBA, detected as 3-ABA, in the extracts was found as a single peak on the chromatograms without any interfering peaks. 3-NBA was detected in 4 incinerator dust samples (n =5). When classified airborne particles, that is, those <1.1, 1.1–2.0, 2.0–3.3, 3.3–7.0, and >7.0μm in size, were applied to the two-dimensional HPLC system after purified using a silica gel column, 3-NBA was detected in those particles with particle sizes <1.1 and 1.1–2.0μm and the particle-size distribution ratios were 84% and 16%, respectively. This is the first report on the particle-size distribution of 3-NBA in airborne particles and the detection of 3-NBA in incinerator dust.
Source:Journal of Chromatography A, Volume 1253
Tomohiro Hasei, Haruka Nakanishi, Yumiko Toda, Tetsushi Watanabe
3-Nitrobenzanthrone (3-NBA) is an extremely strong mutagen and carcinogen in rats inducing squamous cell carcinoma and adenocarcinoma. We developed a new sensitive analytical method, a two-dimensional HPLC system coupled with on-line reduction, to quantify non-fluorescent 3-NBA as fluorescent 3-aminobenzanthrone (3-ABA). The two-dimensional HPLC system consisted of reversed-phase HPLC and normal-phase HPLC, which were connected with a switch valve. 3-NBA was purified by reversed-phase HPLC and reduced to 3-ABA with a catalyst column, packed with alumina coated with platinum, in ethanol. An alcoholic solvent is necessary for reduction of 3-NBA, but 3-ABA is not fluorescent in the alcoholic solvent. Therefore, 3-ABA was separated from alcohol and impurities by normal-phase HPLC and detected with a fluorescence detector. Extracts from surface soil, airborne particles, classified airborne particles, and incinerator dust were applied to the two-dimensional HPLC system after clean-up with a silica gel column. 3-NBA, detected as 3-ABA, in the extracts was found as a single peak on the chromatograms without any interfering peaks. 3-NBA was detected in 4 incinerator dust samples (n =5). When classified airborne particles, that is, those <1.1, 1.1–2.0, 2.0–3.3, 3.3–7.0, and >7.0μm in size, were applied to the two-dimensional HPLC system after purified using a silica gel column, 3-NBA was detected in those particles with particle sizes <1.1 and 1.1–2.0μm and the particle-size distribution ratios were 84% and 16%, respectively. This is the first report on the particle-size distribution of 3-NBA in airborne particles and the detection of 3-NBA in incinerator dust.
Highlights
► We developed new effective analytical method to quantify 3-NBA in environment. ► Two-dimensional HPLC system consisted of reversed- and normal-phase HPLC. ► First report on particle-size distribution of 3-NBA in airborne particles. ► First report on determination of 3-NBA in incinerator dust as a suspected source.Theoretical study of using simulated moving bed chromatography to separate intermediately eluting target compounds
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Jadwiga Nowak, Dorota Antos, Andreas Seidel-Morgenstern
This study deals with the separation of ternary mixtures based on Simulated Moving Bed chromatography to isolate target components with intermediate adsorption strength. To overcome the limitations of conventional SMB systems, which are designed for binary separations and unable to perform center-cut separations, several modifications have been proposed. The purpose of this study was to provide a theoretical comparison of several of advanced SMB configurations capable to separate ternary mixtures. Emphasis is given to those techniques, which have already been used in practice, and to those having potential for future industrial application. SMB cascades connected in series via the extract or raffinate ports of the first unit are analyzed and compared are as well as an integrated 8-zone SMB unit with internal recycle. Additionally, the commercialized pseudo SMB process (JO process) was evaluated. The performance of these modified SMB systems was investigated based on the assumption of linear adsorption isotherms for all three components considering three separation problems characterized by different separation difficulty. Besides the influence of separation factors, the concentrations of the impurities in the feed mixture and the purity requirements for the target product were studied systematically.
Source:Journal of Chromatography A, Volume 1253
Jadwiga Nowak, Dorota Antos, Andreas Seidel-Morgenstern
This study deals with the separation of ternary mixtures based on Simulated Moving Bed chromatography to isolate target components with intermediate adsorption strength. To overcome the limitations of conventional SMB systems, which are designed for binary separations and unable to perform center-cut separations, several modifications have been proposed. The purpose of this study was to provide a theoretical comparison of several of advanced SMB configurations capable to separate ternary mixtures. Emphasis is given to those techniques, which have already been used in practice, and to those having potential for future industrial application. SMB cascades connected in series via the extract or raffinate ports of the first unit are analyzed and compared are as well as an integrated 8-zone SMB unit with internal recycle. Additionally, the commercialized pseudo SMB process (JO process) was evaluated. The performance of these modified SMB systems was investigated based on the assumption of linear adsorption isotherms for all three components considering three separation problems characterized by different separation difficulty. Besides the influence of separation factors, the concentrations of the impurities in the feed mixture and the purity requirements for the target product were studied systematically.
Highlights
► Center-cut separations based on SMB chromatography. ► Theoretical comparison of several advanced SMB configurations. ► System performance investigated for three different separation problems. ► Influence of large amounts of the impurities was studied. ► Different purity requirements for the target product were investigated.Theoretical comparison of the performance of gradient elution chromatography at constant pressure and constant flow rate
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Fabrice Gritti, Georges Guiochon
The theory of gradient elution usually assumes a constant flow rate. This works extends it to gradients performed under constant pressure drop and variable flow rates. The peak capacity is derived under both constant flow rate and constant pressure gradient chromatography by integrating the rate of increase of the peak capacity from the hold-up time to the end of the gradient time. Assuming that the eluent mixture is incompressible, the chromatographic system isothermal, the pressure has no effect on the retention pattern, and neglecting the contributions of the instrument to the total pressure drop and the total peak width, it is found that both modes of gradient elution chromatography are strictly equivalent, provided that the elution time of the last eluted compound and the volume gradient are kept the same in both cases.
Source:Journal of Chromatography A, Volume 1253
Fabrice Gritti, Georges Guiochon
The theory of gradient elution usually assumes a constant flow rate. This works extends it to gradients performed under constant pressure drop and variable flow rates. The peak capacity is derived under both constant flow rate and constant pressure gradient chromatography by integrating the rate of increase of the peak capacity from the hold-up time to the end of the gradient time. Assuming that the eluent mixture is incompressible, the chromatographic system isothermal, the pressure has no effect on the retention pattern, and neglecting the contributions of the instrument to the total pressure drop and the total peak width, it is found that both modes of gradient elution chromatography are strictly equivalent, provided that the elution time of the last eluted compound and the volume gradient are kept the same in both cases.
Highlights
► Classical gradient elution is performed at constant flow rate. ► The flow rate variation when gradient elution is performed with a constant pressure is calculated. ► The peak capacity is calculated for moderate inlet pressures. ► The peak capacity achieved is calculated at constant elution time of the most retained compound. ► The performance of these different modes of operation are compared.Counterion effects on protein adsorption equilibrium and kinetics in polymer-grafted cation exchangers
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Ernie X. Perez Almodovar, Bianca Glatz, Giorgio Carta
Protein binding equilibrium and mass transfer kinetics are studied for cation exchangers containing charged polymer grafts as well as for a macroporous matrix in pH 5 acetate buffers using sodium, tetra-n-butylammonium (TBAH), arginine, and calcium as counterions and a monoclonal antibody (mAb) as a model protein. Dynamic light scattering shows that there is no significant effect of the counterion type on the mAb aqueous diffusivity. The counterion type also does not affect substantially the structure of the polymer grafts, nor does it affect the stoichiometry of the protein ion exchange process. While no counterion effects are also observed on the protein mass transfer kinetics for the macroporous matrix, very large effects are seen for the polymer grafted matrices with protein adsorption rates increasing dramatically in the order Ca++ >Arg+ >Na+ >TBAH+. This order is the same order in which the relative protein binding strength decreases. Accordingly, the counterions leading to weaker protein binding also lead to faster protein diffusion. Although the quantitative aspects are different, the same trends hold for different proteins (lysozyme and lactoferrin) and for an agarose-based matrix also containing grafted polymers (Capto™ S). The underlying mechanism is qualitatively consistent with protein transport occurring through a hopping process driven by the adsorbed protein concentration within the apparently flexible network structure formed by the grafted polymers. From a practical viewpoint, the results show that improved protein adsorption kinetics in polymer-grafted cation exchanger and, hence, improved performance, can be obtained by selecting particular counterions.
Source:Journal of Chromatography A, Volume 1253
Ernie X. Perez Almodovar, Bianca Glatz, Giorgio Carta
Protein binding equilibrium and mass transfer kinetics are studied for cation exchangers containing charged polymer grafts as well as for a macroporous matrix in pH 5 acetate buffers using sodium, tetra-n-butylammonium (TBAH), arginine, and calcium as counterions and a monoclonal antibody (mAb) as a model protein. Dynamic light scattering shows that there is no significant effect of the counterion type on the mAb aqueous diffusivity. The counterion type also does not affect substantially the structure of the polymer grafts, nor does it affect the stoichiometry of the protein ion exchange process. While no counterion effects are also observed on the protein mass transfer kinetics for the macroporous matrix, very large effects are seen for the polymer grafted matrices with protein adsorption rates increasing dramatically in the order Ca++ >Arg+ >Na+ >TBAH+. This order is the same order in which the relative protein binding strength decreases. Accordingly, the counterions leading to weaker protein binding also lead to faster protein diffusion. Although the quantitative aspects are different, the same trends hold for different proteins (lysozyme and lactoferrin) and for an agarose-based matrix also containing grafted polymers (Capto™ S). The underlying mechanism is qualitatively consistent with protein transport occurring through a hopping process driven by the adsorbed protein concentration within the apparently flexible network structure formed by the grafted polymers. From a practical viewpoint, the results show that improved protein adsorption kinetics in polymer-grafted cation exchanger and, hence, improved performance, can be obtained by selecting particular counterions.
Highlights
► The nature of the counterion affects protein adsorption kinetics in polymer-grafted cation exchangers but not in macroporous matrices. ► Arginine and calcium ion provide the greatest enhancement of the protein adsorption kinetics in polymer-grafted matrices. ► Protein adsorption kinetics and protein binding strength are inversely correlated in polymer-grafted media.Determination of 20 coccidiostats in egg and avian muscle tissue using ultra high performance liquid chromatography–tandem mass spectrometry
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Mary Moloney, Lesa Clarke, John O’Mahony, Anna Gadaj, Richard O’Kennedy, Martin Danaher
A quantitative, comprehensive multiresidue method which includes 20 coccidiostat residues has been developed. The method described uses a simple one-step liquid extraction with acetonitrile to isolate analytes from both the polyether ionophore and chemical classes of coccidiostats. Subsequent to a further concentration step, samples were analysed via UHPLC–MS/MS. The method was validated according to the Commission Decision 2002/657/EEC in egg and avian muscle. The method permitted quantitative confirmation for 13 compounds below target concentrations, and screening for a further 7 compounds. Within-laboratory repeatability gave accuracy values in the range of 68–129%, while reproducibility ranged between 75 and 123%. Calibration ranges were typically 1–50μgkg−1, although higher ranges were used for dinitrocarbanilide, imidocarb and toltrazuril residues. A regression coefficient (R 2) value of greater than 0.98 was obtained for all analytes. Precision results ranged from 2.3 to 19.7% CV for egg and from 2.6 to 23.6% CV in muscle. CCα was in the range from 1.13μgkg−1 (clopidol) to 179μgkg−1 (lasalocid) in egg. In muscle, CCα ranged from 2.25μgkg−1 (aprinocid) to 4579μgkg−1 (dinitrocarbanilide). CCβ was from 1.29μgkg−1 (clopidol) to 209μgkg−1 (lasalocid) in egg, and 2.58μgkg−1 (arprinocid) to 6060μgkg−1 (dinitrocarbanilide) in muscle. Limits of quantification were 1μgkg−1 for all compounds, except imidocarb and dinitrocarbanilide (10μgkg−1), and toltrazuril and metabolites (50μgkg−1).
Source:Journal of Chromatography A, Volume 1253
Mary Moloney, Lesa Clarke, John O’Mahony, Anna Gadaj, Richard O’Kennedy, Martin Danaher
A quantitative, comprehensive multiresidue method which includes 20 coccidiostat residues has been developed. The method described uses a simple one-step liquid extraction with acetonitrile to isolate analytes from both the polyether ionophore and chemical classes of coccidiostats. Subsequent to a further concentration step, samples were analysed via UHPLC–MS/MS. The method was validated according to the Commission Decision 2002/657/EEC in egg and avian muscle. The method permitted quantitative confirmation for 13 compounds below target concentrations, and screening for a further 7 compounds. Within-laboratory repeatability gave accuracy values in the range of 68–129%, while reproducibility ranged between 75 and 123%. Calibration ranges were typically 1–50μgkg−1, although higher ranges were used for dinitrocarbanilide, imidocarb and toltrazuril residues. A regression coefficient (R 2) value of greater than 0.98 was obtained for all analytes. Precision results ranged from 2.3 to 19.7% CV for egg and from 2.6 to 23.6% CV in muscle. CCα was in the range from 1.13μgkg−1 (clopidol) to 179μgkg−1 (lasalocid) in egg. In muscle, CCα ranged from 2.25μgkg−1 (aprinocid) to 4579μgkg−1 (dinitrocarbanilide). CCβ was from 1.29μgkg−1 (clopidol) to 209μgkg−1 (lasalocid) in egg, and 2.58μgkg−1 (arprinocid) to 6060μgkg−1 (dinitrocarbanilide) in muscle. Limits of quantification were 1μgkg−1 for all compounds, except imidocarb and dinitrocarbanilide (10μgkg−1), and toltrazuril and metabolites (50μgkg−1).
Highlights
► This paper reports the most comprehensive assay for coccidiostats. ► The method permits the analysis of 20 residues by LC–MS/MS. ► The method was extensively validated according to 2002/657/EC criteria. ► A rigorous validation was completed in egg and avian muscle tissues.Trace adsorption of positively charged proteins onto Sepharose FF and Sepharose FF-based anion exchangers
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Lin-Ling Yu, Yan Sun
Agarose-based matrices have been widely used in ion exchange chromatography (IEC). We have herein observed that positively charged proteins (lysozyme and cytochrome c) are adsorbed on the agarose-based anion-exchangers (Q and DEAE Sepharose FF gels) in a capacity of 10–40μg/mL. In contrast, negatively charged protein (bovine serum albumin) is not adsorbed to Sepharose FF and SP Sepharose FF gels. Elemental analysis of the gel indicated that the residual anionic sulfate groups in agarose would have worked as the cation exchange groups for the positively charged proteins. The trace adsorption behavior of lysozyme onto Sepharose FF and Sepharose FF-based anion exchangers was studied and the effects of NaCl concentration and cation group density on the adsorption were examined for better understanding of the trace adsorption in chromatographic processes. At NaCl concentrations less than 0.05mol/L, which is the normal adsorption condition in IEC, the trace adsorption kept at a high level, so this trace adsorption cannot be avoided in the ionic strength range of routine IEC operations. Grafting poly(ethylenimine) (PEI) chain of 60kDa to a cation group density of 700mmol/L could reduce the adsorption capacity to about 20μg/mL, but further reduction was not possible by increasing the cation group density to 1200mmol/L. Therefore, attentions need to be paid to the phenomenon in protein purification practice using agarose-based matrices. The research is expected to call attentions to the trace adsorption on agarose-based matrices and to the importance in the selection of the suitable solid matrices in the production of high-purity protein products in large-scale bioprocesses.
Source:Journal of Chromatography A, Volume 1253
Lin-Ling Yu, Yan Sun
Agarose-based matrices have been widely used in ion exchange chromatography (IEC). We have herein observed that positively charged proteins (lysozyme and cytochrome c) are adsorbed on the agarose-based anion-exchangers (Q and DEAE Sepharose FF gels) in a capacity of 10–40μg/mL. In contrast, negatively charged protein (bovine serum albumin) is not adsorbed to Sepharose FF and SP Sepharose FF gels. Elemental analysis of the gel indicated that the residual anionic sulfate groups in agarose would have worked as the cation exchange groups for the positively charged proteins. The trace adsorption behavior of lysozyme onto Sepharose FF and Sepharose FF-based anion exchangers was studied and the effects of NaCl concentration and cation group density on the adsorption were examined for better understanding of the trace adsorption in chromatographic processes. At NaCl concentrations less than 0.05mol/L, which is the normal adsorption condition in IEC, the trace adsorption kept at a high level, so this trace adsorption cannot be avoided in the ionic strength range of routine IEC operations. Grafting poly(ethylenimine) (PEI) chain of 60kDa to a cation group density of 700mmol/L could reduce the adsorption capacity to about 20μg/mL, but further reduction was not possible by increasing the cation group density to 1200mmol/L. Therefore, attentions need to be paid to the phenomenon in protein purification practice using agarose-based matrices. The research is expected to call attentions to the trace adsorption on agarose-based matrices and to the importance in the selection of the suitable solid matrices in the production of high-purity protein products in large-scale bioprocesses.
Highlights
► Positively charged proteins were adsorbed on Q and DEAE Sepharose FF at 10–40μg/mL. ► The residual sulfate monoesters on agarose would have caused the trace adsorption. ► Lysozyme adsorption was reduced by grafting poly(ethylenimine) to 700mmol/L. ► The trace adsorption would compromise product purity and/or recovery.Development of a sensitive and robust liquid chromatography coupled with tandem mass spectrometry and a pressurized liquid extraction for the determination of aflatoxins and ochratoxin A in animal derived foods
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Dongmei Chen, Xiaoqin Cao, Yanfei Tao, Qinghua Wu, Yuanhu Pan, Lingli Huang, Xu Wang, Yulian Wang, Dapeng Peng, Zhenli Liu, Zonghui Yuan
A liquid chromatography–tandem mass spectrometry (LC–MS/MS) with a pressurized liquid extraction (PLE) was developed for the simultaneous determination of aflatoxins B1, B2, G1, G2, M1 and M2, and ochratoxin A in the muscle, liver, kidney and fat of swine, bovine and sheep, muscle and liver of chicken, muscle and skin of fish, as well as in hen eggs and dairy milk. Samples were extracted with PLE and cleaned-up with solid phase extraction (SPE) on HLB cartridges. The optimum extraction conditions were obtained as a 11ml ASE cell, acetonitrile/hexane as the extraction solvent, 1500psi, 100°C, a 5min static time and a 60% flush volume. A cheaper and widely used SPE column (Oasis HLB) was applied during clean up. The detection and quantification of the 7 mycotoxins were performed by a reversed-phase liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (LC/ESI-MS/MS). The limits of detection defined as CCα varied from 0.07μg/kg to 0.59μg/kg. The recoveries of spiked samples from 0.25μg/kg to 1μg/kg ranged from 68.3% to 105.7% with the relative standard deviations of less than 17.6%. Performances of the whole analytical procedure met the criteria established by the European Commission for mass spectrometric detection.
Source:Journal of Chromatography A, Volume 1253
Dongmei Chen, Xiaoqin Cao, Yanfei Tao, Qinghua Wu, Yuanhu Pan, Lingli Huang, Xu Wang, Yulian Wang, Dapeng Peng, Zhenli Liu, Zonghui Yuan
A liquid chromatography–tandem mass spectrometry (LC–MS/MS) with a pressurized liquid extraction (PLE) was developed for the simultaneous determination of aflatoxins B1, B2, G1, G2, M1 and M2, and ochratoxin A in the muscle, liver, kidney and fat of swine, bovine and sheep, muscle and liver of chicken, muscle and skin of fish, as well as in hen eggs and dairy milk. Samples were extracted with PLE and cleaned-up with solid phase extraction (SPE) on HLB cartridges. The optimum extraction conditions were obtained as a 11ml ASE cell, acetonitrile/hexane as the extraction solvent, 1500psi, 100°C, a 5min static time and a 60% flush volume. A cheaper and widely used SPE column (Oasis HLB) was applied during clean up. The detection and quantification of the 7 mycotoxins were performed by a reversed-phase liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (LC/ESI-MS/MS). The limits of detection defined as CCα varied from 0.07μg/kg to 0.59μg/kg. The recoveries of spiked samples from 0.25μg/kg to 1μg/kg ranged from 68.3% to 105.7% with the relative standard deviations of less than 17.6%. Performances of the whole analytical procedure met the criteria established by the European Commission for mass spectrometric detection.
Highlights
► The quantification of 7 mycotoxins was performed by a liquid chromatography coupled with triple quadrupole mass spectrometry. ► Pressurized liquid extraction and HLB cartridges were used to extract and clean up mycotoxins residues in animal derived food. ► This method can simultaneously detect more kinds of mycotoxins in animal derived foods.Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part I. A theoretical approach
06 August 2012,
08:49:33
Publication year:
2012
Source:Journal of Chromatography A, Volume 1253
Andreas Håkansson, Emma Magnusson, Björn Bergenståhl, Lars Nilsson
Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.
Source:Journal of Chromatography A, Volume 1253
Andreas Håkansson, Emma Magnusson, Björn Bergenståhl, Lars Nilsson
Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.
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