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Selected papers from the latest issue:
Thin-film octadecyl-silica glass coating for automated 96-blade solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry for analysis of benzodiazepines
24 November 2011, 00:20:19
Publication year: 2011
Source: Journal of Chromatography A, Available online 23 November 2011
Fatemeh S. Mirnaghi, Maria Rowena N. Monton, Janusz Pawliszyn
A thin-film octadecyl (C18)-silica glass coating was developed as the extraction phase for an automated 96-blade solid-phase microextraction (SPME) system coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Various factors (e.g., sol-gel composition and aging time, coating preparation speed, coating thickness, and drying conditions) affecting the quality the C18-silica glass thin-film coating were studied and optimized. The results showed that the stability and durability of the coating are functions of the coating thickness and drying conditions. Coating thickness is controlled by sol-gel composition, aging time and the withdrawal speed in the dipping method. Automated sample preparation was achieved by using a robotic autosampler that enabled simultaneous preparation of 96 samples in a 96-well plate format. Under the optimum SPME conditions the proposed system requires a total 140 min for preparation of all 96 samples (i.e., 30 min preconditioning, 40 min equilibrium extraction, 40 min desorption and 30 min carry over step). The performance of the C18-silica glass 96-blade SPME system was evaluated for high-throughput analysis of benzodiazepines from phosphate-buffered saline solution (PBS) and human plasma, and the reusability, repeatability, and validity of the system were evaluated. When analysing spiked PBS and human plasma, the inter–blade reproducibility for four benzodiazepines was obtained in the ranges of 4-8% and 9-11% RSD (relative standard deviation), respectively, and intra-blade reproducibility were in the ranges of 3-9% and 8-13% RSD, respectively. The limits of detection and quantitation for plasma analysis were in the ranges of 0.4-0.7 ng/mL and 1.5-2.5 ng/mL for all four analytes.
Source: Journal of Chromatography A, Available online 23 November 2011
Fatemeh S. Mirnaghi, Maria Rowena N. Monton, Janusz Pawliszyn
A thin-film octadecyl (C18)-silica glass coating was developed as the extraction phase for an automated 96-blade solid-phase microextraction (SPME) system coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Various factors (e.g., sol-gel composition and aging time, coating preparation speed, coating thickness, and drying conditions) affecting the quality the C18-silica glass thin-film coating were studied and optimized. The results showed that the stability and durability of the coating are functions of the coating thickness and drying conditions. Coating thickness is controlled by sol-gel composition, aging time and the withdrawal speed in the dipping method. Automated sample preparation was achieved by using a robotic autosampler that enabled simultaneous preparation of 96 samples in a 96-well plate format. Under the optimum SPME conditions the proposed system requires a total 140 min for preparation of all 96 samples (i.e., 30 min preconditioning, 40 min equilibrium extraction, 40 min desorption and 30 min carry over step). The performance of the C18-silica glass 96-blade SPME system was evaluated for high-throughput analysis of benzodiazepines from phosphate-buffered saline solution (PBS) and human plasma, and the reusability, repeatability, and validity of the system were evaluated. When analysing spiked PBS and human plasma, the inter–blade reproducibility for four benzodiazepines was obtained in the ranges of 4-8% and 9-11% RSD (relative standard deviation), respectively, and intra-blade reproducibility were in the ranges of 3-9% and 8-13% RSD, respectively. The limits of detection and quantitation for plasma analysis were in the ranges of 0.4-0.7 ng/mL and 1.5-2.5 ng/mL for all four analytes.
Highlights
► We examined a thin-film octadecyl (C18)-silica glass coating for high throughput extraction of clinical samples ► high-quality sol-gel-based coating was obtained ► device was used over 100 times for complex biological matrices analysis ► Extraction time was less than 1.5 minutes per sample.Modelling and optimisation of preparative chromatographic purification of europium
24 November 2011, 00:20:19
Publication year: 2011
Source: Journal of Chromatography A, Available online 23 November 2011
Frida Ojala, Mark Max-Hansen, Dejene Kifle, Niklas Borg, Bernt Nilsson
A model commonly used to describe the separation of biomolecules was used to simulate the harsh environment when eluting neodymium, samarium, europium and gadolinium with a hot acid. After calibration, the model was used to optimise the preparative separation of europium, as this is the most valuable of the four elements. A kinetic dispersive model with a Langmuir mobile phase modulator isotherm was used to describe the process. The equilibration constant, the stoichiometric coefficient and the column capacity for the components were calibrated. The model fitted the experimental observations well. Optimisation was achieved using a differential evolution method. As the two objective functions used in optimising the process, productivity and yield, are competing objectives, the result was not a single set point but a Pareto front.
Source: Journal of Chromatography A, Available online 23 November 2011
Frida Ojala, Mark Max-Hansen, Dejene Kifle, Niklas Borg, Bernt Nilsson
A model commonly used to describe the separation of biomolecules was used to simulate the harsh environment when eluting neodymium, samarium, europium and gadolinium with a hot acid. After calibration, the model was used to optimise the preparative separation of europium, as this is the most valuable of the four elements. A kinetic dispersive model with a Langmuir mobile phase modulator isotherm was used to describe the process. The equilibration constant, the stoichiometric coefficient and the column capacity for the components were calibrated. The model fitted the experimental observations well. Optimisation was achieved using a differential evolution method. As the two objective functions used in optimising the process, productivity and yield, are competing objectives, the result was not a single set point but a Pareto front.
Highlights
► Modelling of preparative separation of the REE using a strong acid. ► Cerium was a good substitute to the expensive elements in overloaded experiments. ► Optimisation of Eu separation regarding yield and productivity. ► It is possible to model and optimise the harsh system when separating small ions.A two-dimensional, heart-cutting preparative gas chromatograph facilitates highly-resolved single-compound isolations with utility towards compound-specific natural abundance radiocarbon (C) analyses
24 November 2011, 00:20:19
Publication year: 2011
Source: Journal of Chromatography A, Available online 23 November 2011
Gregory Ian Ball, Li Xu, Ann P McNichol, Lihini I. Aluwihare
Motivated by the need to develop clean, high purity preparative enrichments of individual compounds for micro-scale compound-specific natural abundance isotope and radiocarbon (C) analyses, we describe a new two-dimensional, heart-cutting, low-bleed, three-oven,singleGC preparative system, demonstrate its resolving capabilities as applied to a typically complex environmental sample matrix, and investigate the robustness with which it preserves the authigenicC/C andC/C ratios of individual compounds it targets for preparative enrichment. The system is comprised of a programmable temperature vaporizing (PTV) inlet, a single GC oven, two modular, door-mounted, resistively-heated low thermal mass (LTM) columns, a preparative fraction collector (PFC) and a Deans pneumatic switching device which facilitates heart-cutting between the system's 1° and 2° chromatographic dimensions. Further, the system's inlet and trapping parameters are optimized for the efficient preparative enrichment of the methyl ether and ester derivatives of the lignin phenol compound class. The lignin phenols include such compounds as the vanillyl and syringyl aldehydes, ethanones, and acids and are unrivaled biomarkers of terrestrial organic matter, some of which are also important components of fragrances and flavors. Using this suite of compounds, the suitability of this augmented preparative capillary GC (PCGC) system was investigated for micro-scale compound-specific (CS) stable isotope and natural abundance radiocarbon analyses (RA). Analysis of a > 300 injection enrichment scheme reveals the instrument to fractionateC in predictable ways and to preserve the authigenic ΔC of compounds it targets for preparative enrichment to within 6.7 ± 5.0 ‰, demonstrating the promising new utility of such systems towards micro-scale CSRA investigations for which clean and high resolution separation techniques are prerequisite.
Source: Journal of Chromatography A, Available online 23 November 2011
Gregory Ian Ball, Li Xu, Ann P McNichol, Lihini I. Aluwihare
Motivated by the need to develop clean, high purity preparative enrichments of individual compounds for micro-scale compound-specific natural abundance isotope and radiocarbon (C) analyses, we describe a new two-dimensional, heart-cutting, low-bleed, three-oven,singleGC preparative system, demonstrate its resolving capabilities as applied to a typically complex environmental sample matrix, and investigate the robustness with which it preserves the authigenicC/C andC/C ratios of individual compounds it targets for preparative enrichment. The system is comprised of a programmable temperature vaporizing (PTV) inlet, a single GC oven, two modular, door-mounted, resistively-heated low thermal mass (LTM) columns, a preparative fraction collector (PFC) and a Deans pneumatic switching device which facilitates heart-cutting between the system's 1° and 2° chromatographic dimensions. Further, the system's inlet and trapping parameters are optimized for the efficient preparative enrichment of the methyl ether and ester derivatives of the lignin phenol compound class. The lignin phenols include such compounds as the vanillyl and syringyl aldehydes, ethanones, and acids and are unrivaled biomarkers of terrestrial organic matter, some of which are also important components of fragrances and flavors. Using this suite of compounds, the suitability of this augmented preparative capillary GC (PCGC) system was investigated for micro-scale compound-specific (CS) stable isotope and natural abundance radiocarbon analyses (RA). Analysis of a > 300 injection enrichment scheme reveals the instrument to fractionateC in predictable ways and to preserve the authigenic ΔC of compounds it targets for preparative enrichment to within 6.7 ± 5.0 ‰, demonstrating the promising new utility of such systems towards micro-scale CSRA investigations for which clean and high resolution separation techniques are prerequisite.
Highlights
► 2-D, heart-cutting prep-GC offers augmented resolving power over traditional setups. ► μg-scale preparative compound isolations by 2-D prep-GC for radiocarbon analysis. ► PCGC optimization conditions for efficient enrichment of lignin-related compounds. ► Low column bleed implementation of preparative capillary gas chromatography (PCGC).Microwave-assisted purge-and-trap extraction device coupled with gas chromatography and mass spectrometry for the determination of five predominant odors in sediment, fish tissues, and algal cells
24 November 2011, 00:20:19
Publication year: 2011
Source: Journal of Chromatography A, Available online 23 November 2011
Xuwei Deng, Ping Xie, Min Qi, Gaodao Liang, Jun Chen, ...
Off-flavors are among the most troublesome compounds in the environment worldwide. The lack of a viable theory for studying the sources, distribution, and effect of odors has necessitated the accurate measurement of odors from environmental compartments. A rapid and flexible microwave-assisted purge-and-trap extraction device for simultaneously determining five predominant odors, namely, dimethyltrisulfide, 2-methylisoborneol, geosmin, β-cyclocitral and β-ionone, from the primary sources and sinks is demonstrated. This instrument facilitates the extraction and concentration of odors from quite different matrices simultaneously. This device is a solvent-free automated system that does not require cleaning and is timesaving. The calibration curves of the five odor compounds showed good linearity in the range of 1 to 500 ng/L, with correlation coefficients above 0.999 (levels = 7) and with residuals ranging from approximately 77% to 104%. The limits of detection (S/N = 3) were below 0.15 ng/L in algae sample and 0.07 ng/g in sediment and fish tissue samples. The relative standard deviations were between 2.65% and 7.29% (n = 6). Thus the proposed design is ready for rapid translation into a standard analytical tool and is useful for multiple applications in the analysis of off-flavors.
Source: Journal of Chromatography A, Available online 23 November 2011
Xuwei Deng, Ping Xie, Min Qi, Gaodao Liang, Jun Chen, ...
Off-flavors are among the most troublesome compounds in the environment worldwide. The lack of a viable theory for studying the sources, distribution, and effect of odors has necessitated the accurate measurement of odors from environmental compartments. A rapid and flexible microwave-assisted purge-and-trap extraction device for simultaneously determining five predominant odors, namely, dimethyltrisulfide, 2-methylisoborneol, geosmin, β-cyclocitral and β-ionone, from the primary sources and sinks is demonstrated. This instrument facilitates the extraction and concentration of odors from quite different matrices simultaneously. This device is a solvent-free automated system that does not require cleaning and is timesaving. The calibration curves of the five odor compounds showed good linearity in the range of 1 to 500 ng/L, with correlation coefficients above 0.999 (levels = 7) and with residuals ranging from approximately 77% to 104%. The limits of detection (S/N = 3) were below 0.15 ng/L in algae sample and 0.07 ng/g in sediment and fish tissue samples. The relative standard deviations were between 2.65% and 7.29% (n = 6). Thus the proposed design is ready for rapid translation into a standard analytical tool and is useful for multiple applications in the analysis of off-flavors.
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