摘要:

AbstractAlthough coupled liquid chromatographygas chromatography (LC‐GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC‐GC applications have been published in the last two years (1987–88) alone. This review categorizes LC‐GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled‐column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on‐line trace enrichment‐GC) have also been included i

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractStationary phase crosslinking conditions for fused silica capillary columns were optimized with the use of a factorial design experiment. This experimental strategy was chosen because it provided for the determination of two‐factor interactions. A predictive model was developed for the desired chromatographic performance parameters as a function of the variables of the crosslinking reaction. Confirmatory experiments proved the usefulness of the mathematical model which resulted in the production of capillary columns of superior performance with significant improvements in reproducibilit

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA laboratory working procedure is described for silanization of glass capillaries with bis(cyanopropyl)tetramethyldisiloxane, prior to coating with XE‐60‐L‐valine‐(S)‐α‐phenylethylamide as chiral stationary phase. GC columns thus prepared exhibit good inertness and no long‐term deterioriation of enantioselectivity up to 220°C. A general procedure is given for derivatization of simple and of polyfunctional amino acids, in a batch mixture, simultaneously, and completely at both the N‐ and the C‐terminus and all other protic functions. Within the seven series ofN‐pivaloyl amino acid esters tested (methyl to neopentyl), baseline separation is obtained for allR/Spairs, including t

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIn analogy to the focusing effective in capillary GC, performed with temperature programming but also with sectional cooling of the column inlet as in multidimensional capillary GC, peak focusing can easily be attained in SFC by adjustment of the mobile phase pressure as well as the column temperature. This may be of practical use in connection with sampling techniques giving poor,i.e.broad and unsymmetrical, peak shapes. Such disturbances may occur, for example, in time controlled valve sampling over longer switching times. Generally, all other negative influences on peak shape can be suppressed or compensated by trapping within the column inlet. Special trapping devices and “retention gaps” may also be coupled to the column inlet in order to create narrow starting plug widths. Positive pressure (density) and negative temperature programs give rise to peak compression besides the increase of peak capacity of the separat

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe triglyceride profiles for corn, soybean, sunflower, grapestone, olive and olive husks oils were obtained by high temperature capillary gas chromatography on HT‐FS capillary columns coated with OV‐17‐OH. The data were treated by methods of computerized pattern analysis, involving principal component analysis, discriminant analysis, and hierarchical clustering. A graphical representation of results as “star symbol plots” allows prompt visual recognition of the characteristic profiles and straightforward qualitative identification of unknowns as well as recognition of adul

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA direct and automatic method has been developed for molecular weight (MW) determination and distribution in crude oils and condensates up to C20(340°C) by gas chromatography. Chromatographic separation has been achieved with a 50 m OV‐1 fused silica capillary column, fitted with a pre‐column to eliminate the fraction boiling above 340°C. The internal standard is added for quantification. Approximately 550 peaks have been identified by the use of GC/MS on different paraffinic, naphthenic, and aromatic crude oils or condensate samples. From identification and by correlation with MS group‐type analysis, a carbon number and a hydrocarbon group are attributed to each peak or group of peaks. Further molecular weights have been calculated from these groups. A comparison between results from this GC method and cryometry of narrow and wide fractions shows good agreement, within the precision of cryometry. An automatic identification by computer using programmed temperature indices was used for the direct determination of molecular weight. The final report gives weight percentage, molar percentage, and molecular weight for every boiling range group and hydrocarbo

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIn the present study, the use of gas chromatography (GC) for the determination of amino acids in human cerebrospinal fluid (CSF) is described. Although some amino acids may be determined using a packed column following the removal of glucose, the major interfering component, the inadequate resolution of other amino acids from remaining unidentified components results in poor quantitation. The use of wide bore columns improves reproducibility considerably, but still it does not provide sufficient resolution to enable quantitative determination of all amino acids in human CSF. Good reproducibility data, withCVvalues for all amino acids of 7% or less and recoveries generally between 80% and 100%, can only be obtained using the fused silica open tubular (FSOT) column. Normal amino acid levels are presented for 10 samples of human CSF, which compare well with data previously reported in the literature.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractStudies have been performed on the analysis of 21 amino acids using a fused‐silica open tubular (FSOT) capillary column, and electron‐capture detection (ECD) or flame‐ionization detection (FID). It was shown with theN(O)‐heptafluorobutyryl (HFB) amino acid isobutyl esters that the ECD response was several hundred times more sensitive than the FID response. The relative standard deviation (RSD) of retention relative to norleucine is determined with the ECD. RSD values for allN(O)‐HFB amino acid isobutyl esters are relatively small (≦ 0.5%). This method has been successfully applied to trace analysis of most of the amino acids from fossil brachiopods and b

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractHigh pressure extraction of vegetable fatty oils by supercritical fluid carbon dioxide was investigated. Pressures from 9 to 20 MPa at 40°C were used. The extracts were monitored by high temperature capillary gas chromatography for sterol and tri‐glyceride composition. The quality of the extracted oils was evaluated by numerical taxonomy methods. The extraction products compared well with the characteristics of commercial fatty oils of the same vegetable origin. No significant qualitative variation was detected in the pressure range studi

ISSN:0935-6304    

DOI:10.1002/jhrc.1240120411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY