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Selected papers from the latest issue:
Ozone removal in the collection of carbonyl compounds in air
30 January 2012, 23:15:07
Publication year: 2012
Source: Journal of Chromatography A, Available online 30 January 2012
Shigehisa Uchiyama, Yohei Inaba, Naoki Kunugita
The most widely used method for measuring carbonyl compounds in air is 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by high-performance liquid chromatography (HPLC). However, substantial negative interference caused by the presence of ozone in air has been reported. To avoid the influences of ozone, a potassium iodide scrubber (KI-scrubber) is commonly used. However, when air sampling using a DNPH-cartridge and a KI-scrubber is performed under conditions of high humidity, moist potassium iodide in the KI-scrubber traps carbonyls before they reach the DNPH-cartridge. Moreover, wet KI reacts with I2to form KI3and this oxidative reagent moves to the DNPH-cartridge and destroys the DNPH and DNPhydrazone derivatives. In order to alleviate these problems, new ozone scrubbers (BPE-scrubber, HQ-scrubber) have been developed. BPE-scrubber and HQ-scrubber consist of silica gel particles impregnated withtrans-1,2-bis-(2-pyridyl) ethylene (BPE) and hydroquinone (HQ), respectively. BPE reacts with ozone to form pyridine aldehyde and HQ reacts with ozone to form benzoquinone. The amounts of reducing agent in silica gel (130 mg) for ozone scrubber are 1% w/w for BPE-cartridge; 0.2% w/w for HQ-scrubber. These scrubbers can be used in air containing 140 μg/mof ozone for 24 h at a flow rate of 200 mL/min. When the relative humidity exceeded 80%, KI in the KI-scrubber was gradually moistened and changed to yellow in color. Peak abundance of formaldehyde, acetaldehyde and acetone DNPhydrazones were diminished to 25%, 15%, 2%, respectively, compared with the BPE-scrubber or HQ-scrubber. When using a BPE-scrubber or HQ-scrubber, decomposition of DNPH and DNPhydrazones were not observed at a wide range of relative humidities (3 - 97%).
Source: Journal of Chromatography A, Available online 30 January 2012
Shigehisa Uchiyama, Yohei Inaba, Naoki Kunugita
The most widely used method for measuring carbonyl compounds in air is 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by high-performance liquid chromatography (HPLC). However, substantial negative interference caused by the presence of ozone in air has been reported. To avoid the influences of ozone, a potassium iodide scrubber (KI-scrubber) is commonly used. However, when air sampling using a DNPH-cartridge and a KI-scrubber is performed under conditions of high humidity, moist potassium iodide in the KI-scrubber traps carbonyls before they reach the DNPH-cartridge. Moreover, wet KI reacts with I2to form KI3and this oxidative reagent moves to the DNPH-cartridge and destroys the DNPH and DNPhydrazone derivatives. In order to alleviate these problems, new ozone scrubbers (BPE-scrubber, HQ-scrubber) have been developed. BPE-scrubber and HQ-scrubber consist of silica gel particles impregnated withtrans-1,2-bis-(2-pyridyl) ethylene (BPE) and hydroquinone (HQ), respectively. BPE reacts with ozone to form pyridine aldehyde and HQ reacts with ozone to form benzoquinone. The amounts of reducing agent in silica gel (130 mg) for ozone scrubber are 1% w/w for BPE-cartridge; 0.2% w/w for HQ-scrubber. These scrubbers can be used in air containing 140 μg/mof ozone for 24 h at a flow rate of 200 mL/min. When the relative humidity exceeded 80%, KI in the KI-scrubber was gradually moistened and changed to yellow in color. Peak abundance of formaldehyde, acetaldehyde and acetone DNPhydrazones were diminished to 25%, 15%, 2%, respectively, compared with the BPE-scrubber or HQ-scrubber. When using a BPE-scrubber or HQ-scrubber, decomposition of DNPH and DNPhydrazones were not observed at a wide range of relative humidities (3 - 97%).
Highlights
► New ozone scrubbers for the collection of carbonyl compounds are described. ► New ozone scrubbers are able to collect carbonyl compounds under high humidity conditions. ► New ozone scrubbers are able to measure simultaneously ozone and carbonyl compounds in air.Operational-Modes of Field-Flow Fractionation in Microfluidic Channels
30 January 2012, 23:15:07
Publication year: 2012
Source: Journal of Chromatography A, Available online 30 January 2012
T.N. Shendruk, G.W. Slater
Through a careful consideration of the retention ratio for Field-Flow Fractionation (FFF), we show that a single unified ideal retention theory can predict a wide range of separation behaviours including hydrodynamic chromatography, normal-mode FFF and steric-mode FFF by introducing the concept of adevice retention ratio. We determine the critical device retention parameter above which normal-mode does not exist and there is no clear distinction between hydrodynamic chromatograghy and steric-mode FFF. Numerical analysis of the elution order as a function of particle size quantitatively predicts the transitions between these regimes. The resulting map of the operational-modes shows each of the regions and their connectivity, and so may guide future device design. By extending this analysis to account for the variation of stress over particle surfaces, a hitherto unreported regime calledFaxén-modeFFF is predicted, which has the same elution order as normal-mode FFF. This mode arises when particle sizes approach the channel height, as occurs when microfluidic devices are utilized for FFF. The transition from steric-mode to Faxén-mode FFF is numerically mapped and approximations for each transition is presented.
Source: Journal of Chromatography A, Available online 30 January 2012
T.N. Shendruk, G.W. Slater
Through a careful consideration of the retention ratio for Field-Flow Fractionation (FFF), we show that a single unified ideal retention theory can predict a wide range of separation behaviours including hydrodynamic chromatography, normal-mode FFF and steric-mode FFF by introducing the concept of adevice retention ratio. We determine the critical device retention parameter above which normal-mode does not exist and there is no clear distinction between hydrodynamic chromatograghy and steric-mode FFF. Numerical analysis of the elution order as a function of particle size quantitatively predicts the transitions between these regimes. The resulting map of the operational-modes shows each of the regions and their connectivity, and so may guide future device design. By extending this analysis to account for the variation of stress over particle surfaces, a hitherto unreported regime calledFaxén-modeFFF is predicted, which has the same elution order as normal-mode FFF. This mode arises when particle sizes approach the channel height, as occurs when microfluidic devices are utilized for FFF. The transition from steric-mode to Faxén-mode FFF is numerically mapped and approximations for each transition is presented.
Highlights
► Particle size is explicitly included in an ideal retention theory for FFF. ► We map the transition from normal-mode to steric-mode FFF. ► We show the hydrodynamic chromatography limit and map the transition to normal-mode. ► We predict a new FFF regime for microfluidic devices called Faxén-mode FFF.Separation of alcohol soluble sorghum proteins using non-porous cation-exchange columns
30 January 2012, 23:15:07
Publication year: 2012
Source: Journal of Chromatography A, Available online 29 January 2012
Deidre L. Blackwell, Scott R. Bean
Kafirins, the storage proteins and major protein of the cereal grain sorghum, play an important nutritional role for millions of people in parts of Africa and Asia. Kafirins are non-water soluble, being soluble only in the presence of detergents or aqueous alcohol mixtures and are among the most hydrophobic of the cereal proteins. Limited Mwheterogeneity of kafirins reduces their resolution when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Charge based separation techniques have been shown to have improved resolution of kafirins, but due to the nature of their solubility, ion-exchange (IE)- HPLC has not been widely used to separate these proteins. To overcome issues of solubility, two different mobile phases were evaluated. The first mobile phase was based on 60% acetonitrile at acidic pH using guanidine-hydrochloride (Gdn-HCl) gradients to elute the proteins from a non-porous cation-exchange column. The second mobile phase tested consisted of 60% acetonitrile using an increasing concentration gradient of a triethylamine phosphate (TEAP) buffer at pH 3.0. The type of alkylation reagent used to stabilize kafirin extracts prior to analysis was found to have an impact on the IE-HPLC separations with the reagent 4-vinylpyridine providing the best resolution. Separations of kafirins in the TEAP mobile phase system resulted in 10 major peaks being resolved. Combining IE-HPLC with reverse phase (RP)- HPLC into 2D separations revealed that the α-kafirins clustered into three major groups not readily apparent in either 1D separation.
Source: Journal of Chromatography A, Available online 29 January 2012
Deidre L. Blackwell, Scott R. Bean
Kafirins, the storage proteins and major protein of the cereal grain sorghum, play an important nutritional role for millions of people in parts of Africa and Asia. Kafirins are non-water soluble, being soluble only in the presence of detergents or aqueous alcohol mixtures and are among the most hydrophobic of the cereal proteins. Limited Mwheterogeneity of kafirins reduces their resolution when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Charge based separation techniques have been shown to have improved resolution of kafirins, but due to the nature of their solubility, ion-exchange (IE)- HPLC has not been widely used to separate these proteins. To overcome issues of solubility, two different mobile phases were evaluated. The first mobile phase was based on 60% acetonitrile at acidic pH using guanidine-hydrochloride (Gdn-HCl) gradients to elute the proteins from a non-porous cation-exchange column. The second mobile phase tested consisted of 60% acetonitrile using an increasing concentration gradient of a triethylamine phosphate (TEAP) buffer at pH 3.0. The type of alkylation reagent used to stabilize kafirin extracts prior to analysis was found to have an impact on the IE-HPLC separations with the reagent 4-vinylpyridine providing the best resolution. Separations of kafirins in the TEAP mobile phase system resulted in 10 major peaks being resolved. Combining IE-HPLC with reverse phase (RP)- HPLC into 2D separations revealed that the α-kafirins clustered into three major groups not readily apparent in either 1D separation.
An improved hollow fiber solvent-stir bar microextraction for the preconcentration of anabolic steroids in biological matrix with determination by gas chromatography-mass spectrometry
30 January 2012, 23:15:07
Publication year: 2012
Source: Journal of Chromatography A, Available online 29 January 2012
Wei Liu, Lan Zhang, Liangbiao Fan, Zian Lin, Yimin Cai, ...
In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent “bar” not floating at the sample solutionorand exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15 μL toluene, 40 °C, stirring at 750 rpm for 30 min with 1.5 g sodium chloride addition in 20.0 mL donor phase), the linear ranges of anabolic steroids were 0.25-200 ng mLwith gas chromatograph-mass spectrometry. The limits of detection were lower than 0.10 ng mL. The recoveries and precisions in spiked urine and hair samples were between 73.97%-93.56% and 2.18%-4.47% (n = 5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in-situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method.
Source: Journal of Chromatography A, Available online 29 January 2012
Wei Liu, Lan Zhang, Liangbiao Fan, Zian Lin, Yimin Cai, ...
In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent “bar” not floating at the sample solutionorand exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15 μL toluene, 40 °C, stirring at 750 rpm for 30 min with 1.5 g sodium chloride addition in 20.0 mL donor phase), the linear ranges of anabolic steroids were 0.25-200 ng mLwith gas chromatograph-mass spectrometry. The limits of detection were lower than 0.10 ng mL. The recoveries and precisions in spiked urine and hair samples were between 73.97%-93.56% and 2.18%-4.47% (n = 5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in-situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method.
Highlights
► A new self-assembled hollow fiber solvent-stir bar microextraction device was developed. ► The proposed device can reduced the vaporization of organic solvents. ► This design could improve the precisions and recoveries of experiments. ► For evaluating the device, anabolic steroids were used as model analytes ► This device could be used in multiple mode of solvent bar microextraction.Preparation and Characterization of Methacrylate-Based Monolith for Capillary Hydrophilic Interaction Chromatography
30 January 2012, 23:15:07
Publication year: 2012
Source: Journal of Chromatography A, Available online 29 January 2012
Ming-Luan Chen, Li-Man Li, Bi-Feng Yuan, Qiao Ma, Yu-Qi Feng
In current study, poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) monolith was successfully prepared for capillary hydrophilic liquid chromatography (cHILIC). The polymerization was optimized by changing the ratio of MAA to EDMA, the type and amount of porogen. The characterization indicated that “hydrophilic” monolithic column possessed homogeneous column bed, good permeability and narrow pore size distribution. Under HILIC mode, the “hydrophilic” monolith prepared with PEG and DMSO showed stronger hydrophilicity than the “hydrophobic” monolith prepared with dodecanol and toluene. Finally, the “hydrophilic” monolith was applied in the separation of tryptic digests of bovine serum albumin (BSA) withcHILIC-ESI-qTOF-MS system. Our results revealed that 49 peptides were identified with 50% sequence coverage under HILIC mode, which was much better than the peptides identified using particulate-packed commercial column with RPLC-ESI-qTOF-MS system or “hydrophobic” monolith withcHILIC-ESI-qTOF-MS system. Taken together, the “hydrophilic” monolithic column prepared in current study, demonstrated the excellent chromatographic performance on the separation of complex samples, which offers the potential application of the monolith on proteomics study.
Source: Journal of Chromatography A, Available online 29 January 2012
Ming-Luan Chen, Li-Man Li, Bi-Feng Yuan, Qiao Ma, Yu-Qi Feng
In current study, poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) monolith was successfully prepared for capillary hydrophilic liquid chromatography (cHILIC). The polymerization was optimized by changing the ratio of MAA to EDMA, the type and amount of porogen. The characterization indicated that “hydrophilic” monolithic column possessed homogeneous column bed, good permeability and narrow pore size distribution. Under HILIC mode, the “hydrophilic” monolith prepared with PEG and DMSO showed stronger hydrophilicity than the “hydrophobic” monolith prepared with dodecanol and toluene. Finally, the “hydrophilic” monolith was applied in the separation of tryptic digests of bovine serum albumin (BSA) withcHILIC-ESI-qTOF-MS system. Our results revealed that 49 peptides were identified with 50% sequence coverage under HILIC mode, which was much better than the peptides identified using particulate-packed commercial column with RPLC-ESI-qTOF-MS system or “hydrophobic” monolith withcHILIC-ESI-qTOF-MS system. Taken together, the “hydrophilic” monolithic column prepared in current study, demonstrated the excellent chromatographic performance on the separation of complex samples, which offers the potential application of the monolith on proteomics study.
Highlights
► A novel hydrophilic monolithic column was described. ► The monolith was optimized in details by using different types of porogen. ► The effect of porogens on surface property and porous structure was investigated. ► The monolith efficiently separated BSA tryptic digests oncHILIC-ESI-qTOF-MS.Optimization of an Improved Single-Column Chromatographic Process for the Separation of Enantiomers
29 January 2012, 02:05:45
Publication year: 2012
Source: Journal of Chromatography A, Available online 26 January 2012
Kazi Monzure Khoda, Bijan Medi, Mohammad Amanullah
This work addresses optimization of an improved single-column chromatographic (ISCC) process for the separation of guaifenesin enantiomers. Conventional feed injection and fraction collection systems have been replaced with customized components facilitating simultaneous separation and online monitoring with the ultimate objective of application of an optimizing controller. Injection volume, cycle time, desorbent flow rate, feed concentration, and three cut intervals are considered as decision variables. A multi-objective optimization technique based on genetic algorithm (GA) is adopted to achieve maximum productivity and minimum desorbent requirement in the region constrained by product specifications and hardware limitations. The optimization results along with the contribution of decision variables are discussed using Pareto fronts that identify non-dominated solutions. Optimization results of a similar simulated moving bed process have also been included to facilitate comparison with a continuous chromatographic process.
Source: Journal of Chromatography A, Available online 26 January 2012
Kazi Monzure Khoda, Bijan Medi, Mohammad Amanullah
This work addresses optimization of an improved single-column chromatographic (ISCC) process for the separation of guaifenesin enantiomers. Conventional feed injection and fraction collection systems have been replaced with customized components facilitating simultaneous separation and online monitoring with the ultimate objective of application of an optimizing controller. Injection volume, cycle time, desorbent flow rate, feed concentration, and three cut intervals are considered as decision variables. A multi-objective optimization technique based on genetic algorithm (GA) is adopted to achieve maximum productivity and minimum desorbent requirement in the region constrained by product specifications and hardware limitations. The optimization results along with the contribution of decision variables are discussed using Pareto fronts that identify non-dominated solutions. Optimization results of a similar simulated moving bed process have also been included to facilitate comparison with a continuous chromatographic process.
Highlights
► Conceptual design of an improved single-column chromatographic separation (ISCC) process has been presented. ► The ISCC process has been optimized using a multi-objective evolutionary algorithm. ► Results show that the proposed fraction collection scheme and overlapped peaks can enhance productivity and decrease desorbent requirement.Determination of benzothiazoles and benzotriazoles by using ionic liquid stationary phases in gas chromatography mass spectrometry. Application to their characterization in wastewaters
29 January 2012, 02:05:45
Publication year: 2012
Source: Journal of Chromatography A, Available online 26 January 2012
Carmen Domínguez, Carolina Reyes-Contreras, Josep M. Bayona
Benzothiazoles (BTHs) and benzotriazoles (BTRs) belong to a high production volume chemicals widely used in both industrial and household applications. Since they are recalcitrant to biodegradation, they are widespread in the environment. However, the BTHs and BTRs determination in environmental matrices is hindered by the coelution with coextracted organic matter and the poor selectivity in mass spectrometry due to the low mass of their diagnostic ions. Accordingly, this study examines the selectivity and suitability of new commercially available ionic liquid (IL) stationary phases for GC-MS and their application to the determination of BTHs and BTRs in wastewater samples. Five different IL columns were tested and the best results in terms of resolution, peak symmetry and analysis time were obtained with the SLB-IL59.
Source: Journal of Chromatography A, Available online 26 January 2012
Carmen Domínguez, Carolina Reyes-Contreras, Josep M. Bayona
Benzothiazoles (BTHs) and benzotriazoles (BTRs) belong to a high production volume chemicals widely used in both industrial and household applications. Since they are recalcitrant to biodegradation, they are widespread in the environment. However, the BTHs and BTRs determination in environmental matrices is hindered by the coelution with coextracted organic matter and the poor selectivity in mass spectrometry due to the low mass of their diagnostic ions. Accordingly, this study examines the selectivity and suitability of new commercially available ionic liquid (IL) stationary phases for GC-MS and their application to the determination of BTHs and BTRs in wastewater samples. Five different IL columns were tested and the best results in terms of resolution, peak symmetry and analysis time were obtained with the SLB-IL59.
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