摘要:

AbstractSimple procedures are presented for separating the enantiomers of α‐methyldopa, 5‐hydroxytryptophan, tryptophan, triiodothyronine and thyroxine, which require neither special sorbents nor difficult‐to‐obtain or unstable reagents.The method for α‐methyldopa, 5‐hydroxytryptophan and tryptophan is based on the use of L‐phenylalanine copper complex as the chiral constituent of the mobile phase; LiChrosorb® RP‐18 serves as the stationary phase. The procedure for triiodothyronine and thyroxine is grounded on the L‐proline copper complex as the chiral reagent and LiChrosorb® Si 60 as the stationary phase.In all observed cases, the D‐enantiomer is eluted prior to the respective L‐enantiomer. Chirality inversion of the mobile phase (application of the D‐phenylalanine copper complex) reverses the order of elution; a racemic eluent (DL‐phenylalanine copper complex) leads to no separation. In addition to the enantiomers of α‐amino acids, the enantiomers of α‐hydroxy aci

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030602

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

年代:1980

数据来源: WILEY

摘要:

AbstractCoupling several 25 cm × 2 mm ID analytical columns together is a simple and easy way to achieve high resolution HPLC (20,000–50,000 plates). How to do this with commercially available instruments, injectors and detectors is described in the paper.An attractive feature of the long narrow column approach is that the same HPLC set‐up can be used for both fast‐low and slow‐high efficiency separations.High efficiency is essential for really complex natural mixtures, e.g. the hop and beer bitter acids. Some examples a

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030603

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

年代:1980

数据来源: WILEY

摘要:

AbstractThis paper demonstrates how simply and rapidly fatty acid esters of mono‐ and polyhydric alcohols can be separated quantitatively in preparative quantities on Lobar® RP‐8 packed columns. After the separation of unknown mixtures, the isolated esters are identified from spectroscopic data (IR/NMR) and, after saponification of the ester components (fatty acids and alcohols), from the retention times of gas and high‐pressure liquid chromatographic separations. Thus, in particular, sparingly volatile or nonvolatile partial esters of polyhydric alcohols, as well as the long‐chained full esters, can be determined qualitatively and quantitatively.The following fatty acid esters of mono‐ and polyhydric alcohols have been separated: the i‐propylesters of the laurinic and myristinic acids, the i‐butyl‐, i‐octyl‐ and i‐octadecyl‐esters of the palmitinic and stearic acids, the mono‐ and di‐fatty acid esters of the 1,3‐bis‐(2‐hydroxyethyl)‐5,5‐dimethylhydantoins, the mono‐, di‐ and tri‐esters of the trimethylalpropa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030604

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe sensitivity of an FID may change when the carrier gas flow rate changes during a chromatographic run. Sample parts which are eluted at reduced FID sensitivity produce a reduced peak area, hence are discriminated as compared to other components. Sensitivity changes were studied for hydrogen as carrier gas. For the detector tested, differences in the carrier gas flow rates of 1 ml/min shifted the FID sensitivity by 1 to 5% (depending on the fuel gas supply). Thus the stability of the sensitivity is no longer ensured as soon as the carrier gas flow rate is changed manually or by an automatic programmer during an analysis. Sensitivity drifts may also occur during temperature programmed runs with a pressure regulated carrier gas supply since the gas flow through the capillary drops with increasing temperature. Such shifts in the response became noticeable as soon as relatively high carrier gas flow rates combined with long range temperature programmes were used. The typical patterns of such discriminations are shown, closing with a discussion on the possibilities for minimizing such undesired effects.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030605

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe influence of chamber saturation in thin‐layer chromatography on theoretical and experimental parameters of mixture separations were examined. Five different types of chambers for development of chromatograms were taken into consideration. The relation found experimentally differed widely from that calculated using Ościk's equation for different method of carrying out of the chromatographic process. The investigations presented here show the possibility of choosing chromatographic chambers which are optimum for theoretical studies on the process of thin‐layer chromatogr

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030606

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

年代:1980

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030607

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe authors have shown that capillary columns are perfectly adequate for the separation of s‐triazine herbicides and urea herbicides. The method presented remains adequate when the initial molecules are accompanied by some of their metabolite

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030608

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

年代:1980

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030609

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

年代:1980

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030610

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

年代:1980

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240030611

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

年代:1980

数据来源: WILEY