|
| ||
|
|
||
Capillary Gas Chromatography (capillary + gas_chromatography)
Selected AbstractsMass spectrometry in newborn and metabolic screening: historical perspective and future directionsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2009Donald H. Chace Abstract The growth of mass spectrometry (MS) in clinical chemistry has primarily occurred in two areas: the traditional clinical chemistry areas of toxicology and therapeutic drug monitoring and more recent, human genetics and metabolism, specifically inherited disorders of intermediary metabolism and newborn screening. Capillary gas chromatography and electrospray tandem MS are the two most common applications used to detect metabolic disease in screening, diagnostics and disease monitoring of treated patients. A few drops of blood from several million newborn infants are screened annually throughout the world making this the largest application of MS in medicine. Understanding the technique, how it grew from a few dozen samples per week in the early 1990s to increasing daily volume today will provide important information for new tests that either expand newborn screening or screening in other areas of metabolism and endocrinology. There are numerous challenges to the further expansion of MS in clinical chemistry but also many new opportunities in closely related applications. The model of newborn screening and MS in medicine may be useful in developing other applications that go beyond newborns and inherited metabolic disease. As MS continues to expand in clinical chemistry, it is clear that two features will drive its success. These features are excellent selectivity and multiple analyte or profile analysis; features recognized in the 1950s and remain true today. Copyright © 2008 John Wiley & Sons, Ltd. [source] Morphology and chemical composition of metathoracic scent glands in Dolycoris baccarum (Linnaeus, 1758) (Heteroptera: Pentatomidae)ACTA ZOOLOGICA, Issue 3 2008Dilek Durak Abstract One of the general defining characters of the Heteroptera is the presence of metathoracic scent glands (MTG). Using scanning electron microscopy, the morphology of the MTG of Dolycoris baccarum (Linnaeus 1758) (Heteroptera: Pentatomidae) was studied. The MTG belong to the diastomian type. The two glandular pores located between the mesothoracic and metathoracic coxae are associated with ,mushroom-like' structures. The MTG are composed of a reservoir and a pair of lateral glands is connected to the reservoir by a duct. A groove-like structure extends downwards from the ostiole. While this structure is long and wide, its ostiole is oval. Extracts of the volatile fractions from male and female MTG secretions were analysed by capillary gas chromatography,mass spectrometry (GC-MS) and exhibited a typical pentatomid composition. Seventeen chemical compounds were detected in female secretions, whereas 13 chemical compounds were detected in the male secretions. Most chemical compounds were similar between the sexes but were different in their quantities. In this regard, the compounds identified were investigated and the biological functions of the glandular secretions were discussed. In the analyses of the MTG of females of D. baccarum, tridecane (50.97%) was a major odour component and (Z,Z)-4,16-octadecadien-1-ol acetate (0.02%) was a minor odour component. In males, tridecane (50.80%) was a major odour component and 1,2-benzenedicarboxylic acid (0.02%) was a minor odour component. [source] Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds.JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 9 20023-acetylnortricyclanes, Kinetics, XXXIX, mechanisms of the hydration reactions of 1- Abstract The disappearance of 1- and 3-acetylnortricyclanes (1-Ac and 2-Ac) in aqueous perchloric acid was followed by capillary gas chromatography at different temperatures and acid concentrations. 1-Ac is much less reactive than 2-Ac. The activation parameters, solvent deuterium isotope effects and parameters of excess acidity equations were measured and the products studied. 1-Acetylnortricyclane is hydrated according to the A -2 mechanism, i.e. the carbonyl oxygen is protonated in the fast pre-equilibrium and one water molecule attacks at the rate-limiting stage the partially open cyclopropane ring, producing 6-acetyl-2-norborneols. 3-Acetylnortricyclane is hydrated according to the AdE2 mechanism, i.e. the cyclopropane ring is slowly protonated and opened, with subsequent fast attack of water producing 3-, 5- and 7-acetyl-2-norborneols. Copyright © 2002 John Wiley & Sons, Ltd. [source] Ultrasound-assisted dispersive liquid,liquid microextraction coupled with capillary gas chromatography for simultaneous analysis of nine pyrethroids in domestic wastewatersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2010Hongyuan Yan Abstract A simple and rapid ultrasound-assisted dispersive liquid,liquid microextraction method coupled with GC-flame ionization detection was developed for simultaneous determination of nine pyrethroids in domestic wastewater samples. An ultrasound-assisted process was applied to accelerate the formation of the fine cloudy solution using small volume of disperser solvent, which markedly increased the extraction efficiency and reduced the equilibrium time. Various parameters affecting the extraction efficiency were investigated, including the type and volume of extraction solvent and disperser solvent, extraction and ultrasonic time. Good linearity was obtained for all analytes in the range of 0.8,100,,g/L with the correlation coefficient (r2),0.998. The recoveries at three spiking levels ranged from 75.3 to 101.2% with the RSD less than 8.7% (n=5). Under the optimum condition, the enrichment factors for the nine pyrethroids ranged from 728- to 1725-fold. This method offered a good alternative for routine analysis due to its simplicity and reliability. [source] Application of comprehensive multidimensional gas chromatography combined with time-of-flight mass spectrometry (GC×GC-TOFMS) for high resolution analysis of hop essential oilJOURNAL OF SEPARATION SCIENCE, JSS, Issue 5-6 2004Mark T. Roberts Abstract The selection and quality of hops is a major determinant in beer flavour. Brewers acknowledge that distinctive characteristics of different hop varieties can be traced to the composition of their essential oils. The difficulty in characterising complex mixtures such as hop oil using 1-D chromatography is that many compounds co-elute. With the introduction of comprehensive multidimensional capillary gas chromatography (GC×GC), there is a tremendous improvement in the separation power or peak capacity. Recent work using GC×GC with flame ionisation detection has suggested that there may be over 1,000 compounds in hop oil. This work describes the use of GC×GC combined with TOFMS detection (Leco Pegasus 4D instrument) to analyse Target hop oil. The TOFMS spectral acquisition rate of 60 Hz provided sufficient spectra per peak (2-D peak base width of 0.1,0.2 s) for identification (119 components were identified with 45 previously unreported compounds). When analysing results, an advantage of GC×GC coupled to TOFMS is that 2-D chromatograms can be viewed for individual masses that are characteristic of particular functional groups. This allows the analyst to view the various homologous series of compounds although in certain cases coelution may still be present as shown by the esters with mass 75. [source] Approaches to identifying and quantifying polycyclic aromatic hydrocarbons of molecular weight 302 in diesel particulatesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 1-2 2004Jean-Jacques Sauvain Abstract Among the PAH class of compounds, high molecular weight PAH are now considered as relevant cancer inducers, but not all of them have the same biological activity. However, their analysis is difficult, mainly due to the presence of numerous isomers and due to their low volatility. Retention indices (Ri) for 13 dibenzopyrenes and homologues were determined by high-resolution capillary gas chromatography (GC) with four different stationary phases: a 5% phenyl-substituted methylpolysiloxane column (DB-5 ms), a 35% phenyl-substituted methylpolysiloxane column (BPX-35), a 50% phenyl-substituted methylpolysiloxane column (BPX-50), and a 35% trifluoropropylmethyl polysiloxane stationary phase (Rtx-200). Correlations for retention on each phase were investigated by using 8 independent molecular descriptors. Ri has been shown to be linearly correlated to PAH volume, polarisability ,, Hückel-, energy on the four examined columns. Ionisation potential Ip is a fourth variable which improves the regression model for DB-5ms, BPX-35, and BPX-50 column. Correlation coefficients ranging from r 2 = 0.935 to r 2 = 0.952 are then observed. Application of these indices to the identification and quantification of PAH with MW 302 in certified diesel particulate matter SRM 1650a is presented and discussed. [source] Odorous compounds in paperboard as influenced by recycled material and storagePACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2001Gottfried Ziegleder Abstract Many volatile compounds can be identified in unprinted paperboard by means of steam distillation in combination with capillary gas chromatography, mass spectrometry and olfactometry. Paperboards produced with recycled material exhibit additional volatiles which partly contribute to off-odours. Using sniffing techniques, benzaldehyde, acetophenone, 1-octen-3-ol, 1-octen-3-one, 2-nonenal, methylguajacol, butanoic and 3-methyl butanoic acid were identified as the most odorous volatiles. The aromatic substances mainly exude from inks and printing solvents in waste materials used for paperboard manufacturing. During storage under controlled conditions, the microbial load of paperboard decreased slightly, and no odorous metabolic products were generated. Copyright © 2001 John Wiley & Sons, Ltd. [source] Identification and quantitation of phenolic compounds in faecal matrix by capillary gas chromatography and nano-electrospray mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2006Ulrike Knust Very few relevant methods have been described for the detection and quantitation of phenolic compounds in faecal matrix. Extraction with conventional organic solvents such as chloroform/methanol (2:1, Folch reagent), methanol and ethanol (72%) showed high extraction efficiency for lipids and also gave good recovery of the major phenolic compounds present in the matrix. However, in comparison with a newly developed phosphate buffer method, the yield of minor phenolics was negligible when detected by these conventional methods. Conventional methods also lead to contamination of the ion source of the mass spectrometer and rapid deterioration of column performance mostly due to the high concentration of lipids. However, if the faecal matrix is initially extracted with phosphate buffer, and the extract acidified and re-extracted with diethyl ether, the range and yield of phenolic compounds are enhanced and the problem of lipid contamination is substantially alleviated. Following pilot studies and optimisation of the procedure, individual phenolic compounds (n,=,29) were identified by nano-electrospray ionisation mass spectrometry (nano-ESI-MS), nano-ESI-tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GC/EI-MS) and quantitated (n,=,27) by GC/MS in subsets (n,=,5) of faecal samples, collected during the European Agency for Cancer Prevention calcium/fibre intervention study from four European countries (Italy, Germany, Spain and Denmark). A range of phenolic compounds (mainly acids) was detected, dominated by phenylacetic, benzoic, phenylpropionic and m -hydroxyphenylpropionic acids, representing on average 9.91 (93%), 8.25 (92%), 9.45 (95%) and 11.05 (98%) mM in the Italian, German, Spanish and Danish samples, respectively. The new method should enable large epidemiologic, case-control and intervention studies on the relevance of phenolic antioxidants in the aetiology of colorectal cancer to be conducted in the future. Copyright © 2006 John Wiley & Sons, Ltd. [source] The analysis of volatile trace compounds in landfill gases, compost heaps and forest airAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2003Sarah Maillefer Abstract Landfill gas, cryotrapped on a loop fashioned from a length of a capillary gas chromatography (GC) column, was examined for volatile organometallic compounds (VOMCs) and for volatile organic compounds (VOCs) by using GC,mass spectrometry (MS). A large number of organic components were present and many were identified, but the only VOMCs present in high enough concentrations to be detected were trimethylstibine and tetramethyltin. The use of inductively coupled plasma (ICP)-MS as an element-specific detector allowed the identification of a number of other organometallic species in the landfill gas, including trimethylarsine and trimethylbismuth, and, for the first time, butyltrimethyltin and dibutyldimethyltin. The presence of molybdenum hexacarbonyl was confirmed. Gas from a large-scale compost heap and from compost incubated in the laboratory contained iodomethane but no common VOMCs (GC,ICP-MS). Only VOCs were present in forest air (GC,MS). Copyright © 2003 John Wiley & Sons, Ltd. [source] Determination of curcumol in rat plasma by capillary gas chromatography with a hydrogen flame ionization detectorBIOMEDICAL CHROMATOGRAPHY, Issue 4 2010Xiao Zhao Abstract A simple and sensitive capillary gas chromatography with a hydrogen flame ionization detector (GC-FID) method was developed for the determination of curcumol in rat plasma. From a variety of compounds and solvents tested, buagafuran was selected as the internal standard (IS) and acetonitrile was found to be the best protein precipitation agent and solvent for extracting curcumol from plasma and tissues samples. (Buagafuran was used as an internal standard. Curcumol was extracted by a protein precipitation with acetonitrile.) The samples were determined by GC on an HP-5 column (30.0 m × 0.32 mm, 0.25 ,m); inlet volume 2 ,L; split ratio 10 : 1; inlet temperature 250°C; oven temperature 180°C; flow 1.0 mL/·min; FID 250°C; carrier gas N2. The resulting retention times of curcumol and IS were 6.0 and 9.5 min. There was good linearity over the range 0.133,133.3 ,g/mL (r = 0.9999) in plasma samples. The method recoveries were 97.7,102.0% in plasma, and the intra- and inter-day variances (RSD) were less than 15% in all cases. The GC method was applied to develop a pharmacokinetics study in which experimental rats received a single administration of curcumol by intravenous injection. Copyright © 2009 John Wiley & Sons, Ltd. [source] Online coupling of enantioselective capillary gas chromatography with proton nuclear magnetic resonance spectroscopyCHIRALITY, Issue 9 2010Maximilian Kühnle Abstract The hyphenation of enantioselective capillary gas chromatography and mass spectrometry is not always sufficient to distinguish between structural isomers, thus requiring peak identification by NMR spectroscopy. Here the first online coupling of enantioselective capillary gas chromatography with proton nuclear resonance spectroscopy is described for the unfunctionalized chiral alkane 2,4-dimethylhexane resolved on octakis(6- O -methyl-2,3-di- O -pentyl)-,-cyclodextrin at 60°C. NMR allows constitutional and configurational isomers (diastereomers and enantiomers) to be distinguished. Enantiomers display identical spectra at different retention times, which enable an indirect identification of these unfunctionalized alkanes. The presented method is still at an early development stage, and will require instrumental optimization in the future. Chirality 2010. © 2010 Wiley-Liss, Inc. [source] | ||||||||||