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Selected papers from the latest issue:
Low density supercritical fluids precipitation of 9-cis and all trans-β-carotenes enriched particulates from Dunaliella salina
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Jian-Ren Chen , Jia-Jiuan Wu , Justin Chun-Te Lin , Yuan-Chuen Wang , Chiu-Chung Young , Chwen-Jen Shieh , Shih-Lan Hsu , Cheih-Ming J. Chang
In this study, supercritical anti-solvent (SAS) pulverization coupled with reverse phase elution chromatography was employed to isolate 9-cis and trans-β-carotenes from Dunaliella salina. Total concentration of 9-cis (134.7mg/g) and trans-β-carotene (204.2mg/g) was increased from 338.9mg/g of the ultrasonic extract to 859.7mg/g (338.9 for 9-cis and 520.8 for trans) of the elution fraction. The SAS pulverization of the collected fraction further produced submicron-sized particulates containing 932.1mg/g (355.6 for 9-cis and 576.5 for trans) of total β-carotenes with a recovery of 86.3% (83.9% for cis and 87.8% for trans). Effects of two SAS operational conditions on the purity, recovery of total β-carotenes, mean size and morphology of the precipitates were obtained from an experimentally designed method. Generation of micronized particulates enriched with 9-cis and trans-β-carotenes by low-density SAS was proved to be feasible and environmental benign.
Source:Journal of Chromatography A, Volume 1299
Author(s): Jian-Ren Chen , Jia-Jiuan Wu , Justin Chun-Te Lin , Yuan-Chuen Wang , Chiu-Chung Young , Chwen-Jen Shieh , Shih-Lan Hsu , Cheih-Ming J. Chang
In this study, supercritical anti-solvent (SAS) pulverization coupled with reverse phase elution chromatography was employed to isolate 9-cis and trans-β-carotenes from Dunaliella salina. Total concentration of 9-cis (134.7mg/g) and trans-β-carotene (204.2mg/g) was increased from 338.9mg/g of the ultrasonic extract to 859.7mg/g (338.9 for 9-cis and 520.8 for trans) of the elution fraction. The SAS pulverization of the collected fraction further produced submicron-sized particulates containing 932.1mg/g (355.6 for 9-cis and 576.5 for trans) of total β-carotenes with a recovery of 86.3% (83.9% for cis and 87.8% for trans). Effects of two SAS operational conditions on the purity, recovery of total β-carotenes, mean size and morphology of the precipitates were obtained from an experimentally designed method. Generation of micronized particulates enriched with 9-cis and trans-β-carotenes by low-density SAS was proved to be feasible and environmental benign.
Facile fabrication of reduced graphene oxide-encapsulated silica: A sorbent for solid-phase extraction
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Yan-Bo Luo , Gang-Tian Zhu , Xiao-Shui Li , Bi-Feng Yuan , Yu-Qi Feng
In this study, a facile hydrothermal reduction strategy was developed for the preparation of reduced graphene oxide-encapsulated silica (SiO2@rGO). Compared with other conventional methods for the synthesis of SiO2@rGO, the proposed strategy endowed the obtained SiO2@rGO with larger amount of immobilized rGO. The prepared functionalized silica shows remarkable adsorption capacity toward chlorophenols (CPs) and peptides. When it was used as solid-phase extraction (SPE) sorbent, a superior recovery could be obtained compared to commercial sorbents, such as C18 silica, graphitized carbon black and carbon nanotubes. Based on these, the prepared material was used as SPE sorbent for the enrichment of CPs, and a method for the analysis of CPs in water samples was established by coupling SPE with high performance liquid chromatography–ultra violet detection (SPE-HPLC/UV). In addition, the obtained SiO2@rGO was further successfully extended to the enrichment of peptides in bovine serum albumin (BSA) digests.
Source:Journal of Chromatography A, Volume 1299
Author(s): Yan-Bo Luo , Gang-Tian Zhu , Xiao-Shui Li , Bi-Feng Yuan , Yu-Qi Feng
In this study, a facile hydrothermal reduction strategy was developed for the preparation of reduced graphene oxide-encapsulated silica (SiO2@rGO). Compared with other conventional methods for the synthesis of SiO2@rGO, the proposed strategy endowed the obtained SiO2@rGO with larger amount of immobilized rGO. The prepared functionalized silica shows remarkable adsorption capacity toward chlorophenols (CPs) and peptides. When it was used as solid-phase extraction (SPE) sorbent, a superior recovery could be obtained compared to commercial sorbents, such as C18 silica, graphitized carbon black and carbon nanotubes. Based on these, the prepared material was used as SPE sorbent for the enrichment of CPs, and a method for the analysis of CPs in water samples was established by coupling SPE with high performance liquid chromatography–ultra violet detection (SPE-HPLC/UV). In addition, the obtained SiO2@rGO was further successfully extended to the enrichment of peptides in bovine serum albumin (BSA) digests.
Application of a strong anion exchange material in electrostatic repulsion–hydrophilic interaction chromatography for selective enrichment of glycopeptides
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Liwei Cao , Long Yu , Zhimou Guo , Xiuling Li , Xinya Xue , Xinmiao Liang
Glycoproteins are involved in various cellular activities, including inter- and extracellular signaling. However, glycopeptide signals are significantly suppressed by coeluting non-glycosylated peptides in mass spectrometry-based analysis. For detailed elucidation of the biological functions of glycoproteins, selective enrichment of glycopeptides from non-glycosylated peptides is crucial. In the present study, a SAX material, XCharge SAX, was used in a column in the ERLIC mode with the aim of specifically enriching glycopeptides. Enrichment conditions were initially optimized, and selectivity, glycosylation heterogeneity coverage and detection sensitivity of XCharge SAX were subsequently assessed. In the selectivity assessment, glycopeptides were effectively isolated from a peptide mixture (human serum immunoglobulin G (IgG) and human serum albumin digests) and a tryptic digest of human serum using XCharge SAX. In the evaluation of glycosylation heterogeneity coverage, five glycosites and eleven glycopeptides from horseradish peroxidase were identified after enrichment with XCharge SAX. In detection sensitivity assessment, glycopeptides within four orders of magnitude were identified after enrichment with XCharge SAX. In addition, volatile solvents were used in the loading and eluting buffers so that desalting was not necessary for ERLIC fractions. Our results collectively support the utility of XCharge SAX as a suitable chromatographic material for global glycosylation site analysis.
Source:Journal of Chromatography A, Volume 1299
Author(s): Liwei Cao , Long Yu , Zhimou Guo , Xiuling Li , Xinya Xue , Xinmiao Liang
Glycoproteins are involved in various cellular activities, including inter- and extracellular signaling. However, glycopeptide signals are significantly suppressed by coeluting non-glycosylated peptides in mass spectrometry-based analysis. For detailed elucidation of the biological functions of glycoproteins, selective enrichment of glycopeptides from non-glycosylated peptides is crucial. In the present study, a SAX material, XCharge SAX, was used in a column in the ERLIC mode with the aim of specifically enriching glycopeptides. Enrichment conditions were initially optimized, and selectivity, glycosylation heterogeneity coverage and detection sensitivity of XCharge SAX were subsequently assessed. In the selectivity assessment, glycopeptides were effectively isolated from a peptide mixture (human serum immunoglobulin G (IgG) and human serum albumin digests) and a tryptic digest of human serum using XCharge SAX. In the evaluation of glycosylation heterogeneity coverage, five glycosites and eleven glycopeptides from horseradish peroxidase were identified after enrichment with XCharge SAX. In detection sensitivity assessment, glycopeptides within four orders of magnitude were identified after enrichment with XCharge SAX. In addition, volatile solvents were used in the loading and eluting buffers so that desalting was not necessary for ERLIC fractions. Our results collectively support the utility of XCharge SAX as a suitable chromatographic material for global glycosylation site analysis.
Determination of anionic surface active agents using silica coated magnetite nanoparticles modified with cationic surfactant aggregates
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Francisco Pena-Pereira , Regina M.B.O. Duarte , Tito Trindade , Armando C. Duarte
The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica–magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10–C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10–C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8–1.9μgL−1 for C10–C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N =6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples.
Source:Journal of Chromatography A, Volume 1299
Author(s): Francisco Pena-Pereira , Regina M.B.O. Duarte , Tito Trindade , Armando C. Duarte
The development of a novel methodology for extraction and preconcentration of the most commonly used anionic surface active agents (SAAs), linear alkylbenzene sulfonates (LAS), is presented herein. The present method, based on the use of silica–magnetite nanoparticles modified with cationic surfactant aggregates, was developed for determination of C10–C13 LAS homologues. The proposed methodology allowed quantitative recoveries of C10–C13 LAS homologues by using a reduced amount of magnetic nanoparticles. Limits of detection were in the range 0.8–1.9μgL−1 for C10–C13 LAS homologues, while the repeatability, expressed as relative standard deviation (RSD), ranged from 2.0 to 3.9% (N =6). Finally, the proposed method was successfully applied to the analysis of a variety of natural water samples.
Supported liquid membrane extraction coupled in-line to commercial capillary electrophoresis for rapid determination of formate in undiluted blood samples
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Pavla Pantůčková , Pavel Kubáň , Petr Boček
A cheap, disposable sample pretreatment device with planar supported liquid membrane (SLM) was proposed, assembled and placed into an autosampler carousel of a commercial capillary electrophoresis (CE) instrument for automated pretreatment and analysis of formate in undiluted whole blood and serum samples. All analytical procedures except for filling the pretreatment device with donor and acceptor solutions, i.e., extraction across SLM, injection of the extracted sample and CE-UV determination of formate, were performed fully automatically. The pretreatment device required only μL volumes of blood sample and organic solvent per extraction and was disposed off after each extraction. Good repeatability of peak areas (≤7.7%) and migration times (≤1.5%), linear relationship (r 2 =0.998–0.999) and limits of detection (≤35μM) were achieved. The overall analytical process including blood withdrawal, filling the SLM device with respective solutions, extraction of blood sample, injection into separation capillary and CE separation of formate from other anions took less than 4min. The method was proved useful by direct determination of elevated formate concentrations in undiluted serum samples of a methanol intoxicated patient. Due to its compatibility with currently commercially available CE instrumentation, disposability of extraction devices, minimum sample handling/consumption, and short extraction/analysis times, the developed method might be attractive for rapid diagnosis of methanol poisoning in clinical and toxicological laboratories.
Source:Journal of Chromatography A, Volume 1299
Author(s): Pavla Pantůčková , Pavel Kubáň , Petr Boček
A cheap, disposable sample pretreatment device with planar supported liquid membrane (SLM) was proposed, assembled and placed into an autosampler carousel of a commercial capillary electrophoresis (CE) instrument for automated pretreatment and analysis of formate in undiluted whole blood and serum samples. All analytical procedures except for filling the pretreatment device with donor and acceptor solutions, i.e., extraction across SLM, injection of the extracted sample and CE-UV determination of formate, were performed fully automatically. The pretreatment device required only μL volumes of blood sample and organic solvent per extraction and was disposed off after each extraction. Good repeatability of peak areas (≤7.7%) and migration times (≤1.5%), linear relationship (r 2 =0.998–0.999) and limits of detection (≤35μM) were achieved. The overall analytical process including blood withdrawal, filling the SLM device with respective solutions, extraction of blood sample, injection into separation capillary and CE separation of formate from other anions took less than 4min. The method was proved useful by direct determination of elevated formate concentrations in undiluted serum samples of a methanol intoxicated patient. Due to its compatibility with currently commercially available CE instrumentation, disposability of extraction devices, minimum sample handling/consumption, and short extraction/analysis times, the developed method might be attractive for rapid diagnosis of methanol poisoning in clinical and toxicological laboratories.
Polyethersulfone solid-phase microextraction followed by liquid chromatography quadrupole time-of-flight mass spectrometry for benzotriazoles determination in water samples
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): J. Casado , I. Rodríguez , M. Ramil , R. Cela
A microextraction method for the determination of 1H-benzotriazole (BTri), and four polar derivatives (4 and 5-methyl-1H-benzotriazole, 4-TTri and 5-TTri; 5,6-dimethyl-1H-benzotriazole, XTri; and 5-chloro-1H-benzotriazole, 5-ClBTri), in surface and wastewater samples is presented. Analytes were pre-concentrated using a disposable, low cost polyethersulfone (PES) sorbent and further analysed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC–QTOF-MS). Parameters affecting the efficiency of sample preparation (extraction conditions and desorption solvent) and those controlling the performance of LC–MS determination were investigated. Analytes were extracted from 15mL water samples, containing a 30% (w/v) of sodium chloride (4.5g) and adjusted at pH 4.5, using a tubular PES sorbent (5cm length×0.7mm o.d., sorbent volume 42μL). After methanol desorption and solvent exchange, benzotriazoles were determined by LC–MS, with chromatograms extracted using a mass window of 20ppm, centred in their [M+H]+ ions. The identity of chromatographic peaks was confirmed with accurate ion product scan (MS/MS) spectra. The method provided limits of quantification (LOQs) between 0.005 and 0.100μgL−1, and relative recoveries from 81% to 124% (except for XTri in sewage samples, ca. 60%) with associated standard deviations between 2% and 9%. When compared with polydimethylsiloxane covered stir-bars (coating volume 24μL), the PES polymer achieved significant higher responses (5–20-fold) for these polar pollutants. BTri and tolyltriazoles (4-TTri and 5-TTri) were found in urban sewage and river water samples, affected by wastewater discharges, with the maximum concentration (5.9μgL−1) corresponding to BTri in raw wastewater.
Source:Journal of Chromatography A, Volume 1299
Author(s): J. Casado , I. Rodríguez , M. Ramil , R. Cela
A microextraction method for the determination of 1H-benzotriazole (BTri), and four polar derivatives (4 and 5-methyl-1H-benzotriazole, 4-TTri and 5-TTri; 5,6-dimethyl-1H-benzotriazole, XTri; and 5-chloro-1H-benzotriazole, 5-ClBTri), in surface and wastewater samples is presented. Analytes were pre-concentrated using a disposable, low cost polyethersulfone (PES) sorbent and further analysed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC–QTOF-MS). Parameters affecting the efficiency of sample preparation (extraction conditions and desorption solvent) and those controlling the performance of LC–MS determination were investigated. Analytes were extracted from 15mL water samples, containing a 30% (w/v) of sodium chloride (4.5g) and adjusted at pH 4.5, using a tubular PES sorbent (5cm length×0.7mm o.d., sorbent volume 42μL). After methanol desorption and solvent exchange, benzotriazoles were determined by LC–MS, with chromatograms extracted using a mass window of 20ppm, centred in their [M+H]+ ions. The identity of chromatographic peaks was confirmed with accurate ion product scan (MS/MS) spectra. The method provided limits of quantification (LOQs) between 0.005 and 0.100μgL−1, and relative recoveries from 81% to 124% (except for XTri in sewage samples, ca. 60%) with associated standard deviations between 2% and 9%. When compared with polydimethylsiloxane covered stir-bars (coating volume 24μL), the PES polymer achieved significant higher responses (5–20-fold) for these polar pollutants. BTri and tolyltriazoles (4-TTri and 5-TTri) were found in urban sewage and river water samples, affected by wastewater discharges, with the maximum concentration (5.9μgL−1) corresponding to BTri in raw wastewater.
Development of a solid-phase extraction liquid chromatography tandem mass spectrometry method for benzotriazoles and benzothiazoles in wastewater and recycled water
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Clara H. Loi , Francesco Busetti , Kathryn L. Linge , Cynthia A. Joll
Two methods employing solid-phase extraction and liquid chromatography tandem mass spectrometry were developed for the analysis of benzotriazoles (BTs) and benzothiazoles (BThs), compounds which are commonly found in a large variety of commercial and household products. The first method was able to detect 7 BTs and 7 BThs, the largest suite of BTs and BThs analysed in a single method to-date, but could not distinguish between the isomers, 4-methylbenzotriazole (4-MeBT) and 5-methylbenzotriazole (5-MeBT). Therefore, a second method was developed to achieve the chromatographic separation of 4-MeBT and 5-MeBT. The methods were validated for ultrapure water and secondary wastewater, and method limits of detection (MLD) for BTs and BThs (for the primary method) ranged from 0.1 to 58ngL−1 for ultrapure water, and 2 to 322ngL−1 for secondary wastewater. For the secondary method, MLDs for 4- and 5-MeBT ranged from 8 to 12ngL−1 for ultrapure water, and 388 to 406ngL−1 for secondary wastewater. Analysis of secondary wastewater and reverse osmosis (RO) treated water from an advanced water recycling plant in Australia is presented, and represents the first reported data from the analysis of BTs and BThs in recycled water. Some of these compounds were found to persist through wastewater treatment and incompletely removed by RO treatment. Benzotriazole (BT), 4-MeBT, 5-MeBT and 2-(methylthio)benzothiazole were detected in secondary wastewater, however the latter compound was not quantifiable. Concentrations of BT and tolyltriazoles (TTs, i.e. sum of 4- and 5-MeBT, detected with the primary method) in secondary wastewater were 3.3 (±0.02) and 2.8 (±0.04)μgL−1, respectively. These same compounds were also detected in the post-RO water samples at concentrations of 974 (±28)ngL−1 for BT and 416(±34)ngL−1 for TTs. 2-Hydroxybenzothiazole was also detected in the post-RO water samples, however it was not quantifiable. Removal efficiencies for RO treatment were calculated to be between 70% and 85% for BT and TTs.
Source:Journal of Chromatography A, Volume 1299
Author(s): Clara H. Loi , Francesco Busetti , Kathryn L. Linge , Cynthia A. Joll
Two methods employing solid-phase extraction and liquid chromatography tandem mass spectrometry were developed for the analysis of benzotriazoles (BTs) and benzothiazoles (BThs), compounds which are commonly found in a large variety of commercial and household products. The first method was able to detect 7 BTs and 7 BThs, the largest suite of BTs and BThs analysed in a single method to-date, but could not distinguish between the isomers, 4-methylbenzotriazole (4-MeBT) and 5-methylbenzotriazole (5-MeBT). Therefore, a second method was developed to achieve the chromatographic separation of 4-MeBT and 5-MeBT. The methods were validated for ultrapure water and secondary wastewater, and method limits of detection (MLD) for BTs and BThs (for the primary method) ranged from 0.1 to 58ngL−1 for ultrapure water, and 2 to 322ngL−1 for secondary wastewater. For the secondary method, MLDs for 4- and 5-MeBT ranged from 8 to 12ngL−1 for ultrapure water, and 388 to 406ngL−1 for secondary wastewater. Analysis of secondary wastewater and reverse osmosis (RO) treated water from an advanced water recycling plant in Australia is presented, and represents the first reported data from the analysis of BTs and BThs in recycled water. Some of these compounds were found to persist through wastewater treatment and incompletely removed by RO treatment. Benzotriazole (BT), 4-MeBT, 5-MeBT and 2-(methylthio)benzothiazole were detected in secondary wastewater, however the latter compound was not quantifiable. Concentrations of BT and tolyltriazoles (TTs, i.e. sum of 4- and 5-MeBT, detected with the primary method) in secondary wastewater were 3.3 (±0.02) and 2.8 (±0.04)μgL−1, respectively. These same compounds were also detected in the post-RO water samples at concentrations of 974 (±28)ngL−1 for BT and 416(±34)ngL−1 for TTs. 2-Hydroxybenzothiazole was also detected in the post-RO water samples, however it was not quantifiable. Removal efficiencies for RO treatment were calculated to be between 70% and 85% for BT and TTs.
Relative importance of column and adsorption parameters on the productivity in preparative liquid chromatography. I: Investigation of a chiral separation system
27 June 2013,
15:00:01
Publication date: 19 July
2013
Source:Journal of Chromatography A, Volume 1299
Author(s): Patrik Forssén , Jörgen Samuelsson , Torgny Fornstedt
Starting out from an experimental chiral separation system we have used computer simulations for a systematic investigation on how the maximum productivity depends on changes in column length, packing particle size, column efficiency, back pressure, sample concentration/solubility, selectivity, retention factor of the first eluting component and monolayer saturation capacity. The study was performed by changing these parameters, one at a time, and then calculating the corresponding change in maximum productivity. The three most important parameters for maximum production rate was found to be (i) the selectivity (ii) the retention factor of the first eluting component and (iii) the column length. Surprisingly, the column efficiency and sample concentration/solubility were of minor importance. These findings can be used as rough guidelines for column selection, e.g. a low-efficiency column are more likely perform better, in terms of productivity, than a high-efficiency column that have higher retention factor for the first eluting component.
Source:Journal of Chromatography A, Volume 1299
Author(s): Patrik Forssén , Jörgen Samuelsson , Torgny Fornstedt
Starting out from an experimental chiral separation system we have used computer simulations for a systematic investigation on how the maximum productivity depends on changes in column length, packing particle size, column efficiency, back pressure, sample concentration/solubility, selectivity, retention factor of the first eluting component and monolayer saturation capacity. The study was performed by changing these parameters, one at a time, and then calculating the corresponding change in maximum productivity. The three most important parameters for maximum production rate was found to be (i) the selectivity (ii) the retention factor of the first eluting component and (iii) the column length. Surprisingly, the column efficiency and sample concentration/solubility were of minor importance. These findings can be used as rough guidelines for column selection, e.g. a low-efficiency column are more likely perform better, in terms of productivity, than a high-efficiency column that have higher retention factor for the first eluting component.
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