Home About us Contact
|
Home About us Contact | ||
|
|
||
Gas Chromatographic Separation (gas + chromatographic_separation)
Selected AbstractsGas chromatographic separation of saturated aliphatic hydrocarbon enantiomers on permethylated ,-cyclodextrinCHIRALITY, Issue S1 2003Uwe J. Meierhenrich Abstract Enantiomers of chiral aliphatic hydrocarbons are generally difficult to separate because they lack functional groups to be derivatized in order to generate diastereomers. The systematic and quantitative separation of a series of branched hydrocarbon enantiomers using a chiral cyclodextrin stationary phase and a cryostat-controlled gas chromatograph is described. The use of a cryogenic system allows the improvement of separations for various chiral aliphatic hydrocarbons. The molecular cyclodextrin-based mechanism of the achieved enantiomeric separations is discussed briefly. Possible applications of this analytical technique are summarized, with special emphasis on the planned enantiomeric separation experiment on a cometary nucleus. Chirality 15:S13,S16, 2003. © 2003 Wiley-Liss, Inc. [source] A method for the determination of polyunsaturated fatty acid methyl esters in biodiesel: Results of an interlaboratory studyEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 8 2009Sigurd Schober Abstract A gas chromatographic method for the determination of fatty acid methyl esters with four or more double bonds in biodiesel was developed and tested. The method is based on gas chromatographic separation on a wax capillary column using methyl tricosanoate as internal standard. The performance of the method was proved with the participation of 11,European laboratories by a Round Robin test on six different biodiesel samples containing different amounts of polyunsaturated fatty acid methyl esters. The results showed that the precision is sufficient around the EN,14214 limit of 1,% (m/m). At lower concentrations the variation is too high. The scope of the application can be given between as 0.6 and 1.5%. [source] A selective and sensitive approach to characterize odour-active and volatile constituents in small-scale human milk samplesFLAVOUR AND FRAGRANCE JOURNAL, Issue 6 2007Andrea Buettner Abstract A sensitive and selective analytical approach was developed for the characterization of trace volatile and odorous substances in body fluids. The methodology was successfully applied for identification of more than 40 characteristic odorants in human milk. The technique comprises a modified stir bar sorptive extraction system in combination with two-dimensional gas chromatographic separation and parallel mass spectrometric and olfactometric characterization of the analytes. The present study shows that the technique can be used for both direct extractive sampling and headspace analysis, and that it is applicable for small sample volumes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Applications of solid phase microextraction for the determination of metallic and organometallic speciesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 3 2006Varinder Kaur Abstract This paper reviews recent developments of solid phase microextraction (SPME) and its application to the analysis of organometallic species of lead, arsenic, mercury, tin, and selenium by hyphenation with HPLC-GC-atomic spectrometry. In the first part, a background of the technique is given in terms of derivatization, fibers used, extraction and desorption conditions. The second part summarizes typical SPME applications to the determination of organometallic species and the main experimental conditions with the aid of specific examples. Most of the applications comprise alkylation with NaBEt4 and headspace extraction followed by gas chromatographic separation with a suitable detector. [source] Validation of a quantitative assay of arbutin using gas chromatography in Origanum majorana and Arctostaphylos uva-ursi extractsPHYTOCHEMICAL ANALYSIS, Issue 5 2009Aline Lamien-Meda Abstract Introduction , Arbutin is a skin-whitening agent that occurs naturally in the bark and leaves of various plants. It is commonly quantified in plant extracts and skin-whitening products by HPLC. Objective , To develop an alternative gas chromatographic method for the separation and quantification of arbutin in Origanum majorana and Arctostaphylos uva-ursi extracts. Methodology , N,O -Bis(trimethylsilyl)acetamide and trimethylchlorosilane were used as silylation reagents, and the gas chromatographic separation of silylated extracts and standards was performed using a DB-5 narrow bore column. GC-MS was used for the compound identification, and the quantification was carried out by GC-FID. The quantitative results were compared with those of HPLC analysis. Results , The developed method gave a good sensitivity with linearity in the range 0.33,500,mg/mL and recovery >98%, allowing the quantification of arbutin in O. majorana and A. uva-ursi extracts. The relative standard deviations (RSD) relating to intra-day and inter-day precision were <0.002% and <4.8%, respectively. The GC results correlated well with those obtained by HPLC analysis. Conclusion , The analysis of marjoram and bearberry samples showed that the established GC method was rapid, selective, and demonstrated that arbutin could be screened alternatively by gas chromatography. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of community structure through deconvolution of PLFA-FAME signature of mixed populationBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2007Dipesh K. Dey Abstract Phospholipid fatty acids (PLFAs) as biomarkers are well established in the literature. A general method based on least square approximation (LSA) was developed for the estimation of community structure from the PLFA signature of a mixed population where biomarker PLFA signatures of the component species were known. Fatty acid methyl ester (FAME) standards were used as species analogs and mixture of the standards as representative of the mixed population. The PLFA/FAME signatures were analyzed by gas chromatographic separation, followed by detection in flame ionization detector (GC-FID). The PLFAs in the signature were quantified as relative weight percent of the total PLFA. The PLFA signatures were analyzed by the models to predict community structure of the mixture. The LSA model results were compared with the existing "functional group" approach. Both successfully predicted community structure of mixed population containing completely unrelated species with uncommon PLFAs. For slightest intersection in PLFA signatures of component species, the LSA model produced better results. This was mainly due to inability of the "functional group" approach to distinguish the relative amounts of the common PLFA coming from more than one species. The performance of the LSA model was influenced by errors in the chromatographic analyses. Suppression (or enhancement) of a component's PLFA signature in chromatographic analysis of the mixture, led to underestimation (or overestimation) of the component's proportion in the mixture by the model. In mixtures of closely related species with common PLFAs, the errors in the common components were adjusted across the species by the model. Biotechnol. Bioeng. 2007;96: 409,420. © 2006 Wiley Periodicals, Inc. [source] | |||||||||||||