Preparative capillary gas chromatography

Eglinton et al. [688] described a practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This approach uses an automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of... 

S. Blomberg and J. Roeraade, Preparative capillary gas chromatography. II. Fraction collection on traps coated with a very thick-film of immobilized stationary phase , /. Chromatogr. 394 443 -453 (1987). 

I. P. E. M. Rijks and J. A. Rijks, Programmed cold sample introduction and multidimensional preparative capillary gas chromatography. Part I introduction, design and operation of a new mass flow controlled multidimensional GC system , J. High Resolut. Chromatogr. 13 261-266 (1990). 

Identification of these components was based on GC/MS and retention index information. Novel compounds were isolated by preparative capillary gas chromatography and spectroscopically identified by interpretation of infrared, nuclear magnetic resonance and mass spectra. In... 

C. Meinert, E. Schymanski, E. Kiister, R. Kiihne, G. Schiiiirmann, and W. Brack. Application of preparative capillary gas chromatography (pcGC), automated structure generation and mutagenicity prediction to improve effect-directed analysis of genotoxicants in a contaminated groundwater. Environ. Sci. Pollut. Res., 17(4) 885-897, 2010. 

For the enrichment and purification of unknown compound II, the hydrocarbons of about 20 kg of orange essence oil were removed by column chromatography on silica gel. Subsequently the compound occurring in fraction II was further purified by two-dimensional preparative capillary gas chromatography. Interpretation of the resulting mass spectra finally led to the identification of 8-tetradecenal. The mass spectrum is shown in Fig. 2. 

More recendy the cis and trans isomers of the mosquito repellent CIC-4, a mixture of citroneUa isomers, have been separated by preparative hplc and bioassayed for effectiveness (23). Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazoUdine derivatives of (+)-and ( —)-citroneUal have been studied to find stmcture—activity relationships (24). Several 2-aLkyl- -acetyloxahdines have been synthesized and tested against mosquitoes, with further efforts using nmr to determine the rotational isomers of the more active N-acetyl-2,2-dimethyloxazohdine (25). 

The development of this technique has proceeded along several independent paths with two principal lines being elemental analyzer-IRMS and capillary gas chromatography-IRMS. In elemental analyzers, samples are combusted to CO2, N2, SO2, and H2O, which are either chemically trapped or separated on GC columns. The advantages of these techniques are an automated preparation with low costs per sample and a large sample through-put. 

Capillary gas chromatography (GC) using modified cyclodextrins as chiral stationary phases is the preferred method for the separation of volatile enantiomers. Fused-silica capillary columns coated with several alkyl or aryl a-cyclo-dextrin, -cyclodextrin and y-cyclodextrin derivatives are suitable to separate most of the volatile chiral compounds. Multidimensional GC (MDGC)-mass spectrometry (MS) allows the separation of essential oil components on an achiral normal phase column and through heart-cutting techniques, the separated components are led to a chiral column for enantiomeric separation. The mass detector ensures the correct identification of the separated components [73]. Preparative chiral GC is suitable for the isolation of enantiomers [5, 73]. 

On the other hand, capillary gas chromatography with liquid crystals yields very good analytical separations (even for critical pairs of isomers) as the GLC system is used and an inherent lower selectivity compared to cyclodextrins is compensated for by the higher efficiency of the capillary columns Therefore, future work should be directed toward reproducible preparation of capillary columns with cyclodextrins and to other liquid crystals with a higher selectivity ... 

Analysis of trace compounds. All fractions were checked by capillary gas chromatography (GC) with FID and sulfiir specific detection (flame photometric detector, FPD ThermoQuest CE, Egelsbach). Subsequently the different fractions were analyzed by capillary gas chromatography-mass spectrometry (GC-MS). Specific unknowns were enriched by preparative multidimensional gas chromatography (MDGC). For further structure elucidation complementary analyses using GC-MS and capillary gas chromatography-Fourier transform infrared spectroscopy (GC-FTIR) as well as H-NMR were applied. All new compounds have been synthesized and characterized by GC-olfactometry (GC-0). 

Chiral capillary gas chromatography (GC), performed with a 7-cyclodextrin trifluoroacetyl column, was also used for the determination of ee of isoxazolines <2000JOC8527>. Chiral preparative HPLC has been used to obtain optically pure isoxazolines <1997JME50>. 

The method of analysis for the final determination of the seven CB congeners used by each of the participating laboratories was based on capillary gas chromatography with electron capture detection. In addition, mass spectrometry was used for compound identification and confirmation, but not for quantification. Each laboratory used their own proven procedures for the sample preparation, clean-up, method of injection, choice of carrier gas and chromatographic condition. The fish oils were dissolved in an appropriate solvent and analysed without any preliminary extraction from the matrix. 

The final determination of the CBs was performed by capillary gas chromatography with electron capture detection mass spectrometry was used as complementary technique to confirm the identity of each of the CBs determined. Each participant had validated its method by performing experiments on recovery, extraction efficiency, procedure blanks and detector linearity. The seven individual CB calibrants were supplied to the participants as pure, crystalline CRMs from BCR (CRMs Nos. 291,293, 294,295, 296. 297 and 298). Each laboratory was requested to prepare separate calibration solutions of the appropriate concentration, in iso-octane, to calibrate the detector and lying within its linear range. The use of at least one internal standard was mandatory the participants, however, were left free to select the internal standard(s) best suited to their methods. They had to verify that the selected compounds did not occur in the candidate reference material or did not interfere with compounds present in the material. A series of pure dichlorobenzylalkyl ethers (DCBEs) was made available to the participants but other internal standards were also accepted of which the list is given in the certification report [21] along with additional details on calibration procedures. 

High resolution chromatography evolved with the advent of capillary gas chromatography however, this field remained dormant for a long period of time because of difficulties Involved In the preparation of suitable capillary columns. Most of these problems have now been resolved providing an impetus for ultra-high resolution chromatography. 

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