摘要:

Abstract(R)—(+)‐Limonene was photooxidized in the presence of Rose Bengal as catalyst. After TLC isolation, the hydroperoxides formed were separated directly by HRGC and analyzed by MS (El; Cl). Each hydroperoxide isomer was then isolated by HPLC for structure determination which after reduction of the HOO group with sodium borohydride was performed by1H‐NMR and13C‐NMR.Six hydroperoxide isomers formed by oxidation of the endocyclic double bond were identified. The compounds eluted from the HRGC column in the following order (proportions are given in brackets) I (40.1%) (1S, 4R)‐p‐mentha‐2, 8‐diene 1‐hydroperoxide; II (5.8%) (1R, 4R)‐p‐mentha‐2, 8‐diene 1‐hydroperoxide; III (20.6%) (2R, 4R)‐p‐mentha‐[1(7), 8]‐diene 2‐hydroperoxide; IV (8.5%) (2R, 4R)‐p‐mentha‐6, 8‐diene 2‐hydroperoxide; V (4%) (2S, 4R)‐p‐mentha‐6, 8‐diene 2‐hydroperoxide; and VI (21.0%) (2S, 4R)‐p‐mentha‐[1(7), 8]‐diene 2‐hydroperoxide. Direct HRGC separation of the limonene hydroperoxides offers,inter alia, the possibil

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101102

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

年代:1987

数据来源: WILEY

摘要:

AbstractA method is described for the determination of the acid and alcohol moieties in long chain wax esters. The co‐eluting esters are differentiated by means of CGC‐MS operating in the ion monitoring mode. The technique allows to detect ester components present in very low amounts in plant surface wa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101103

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

年代:1987

数据来源: WILEY

摘要:

AbstractSeveral packing materials were evaluated for their sampling performance with a cold programmed temperature vaporizing injector operated in the solvent split (solvent elimination) mode. Evaluations were made by comparing accuracy and precision of the data for mixtures ofn‐alkanes, ethyl esters,n‐alcohols, and carboxylic acids covering polarity and volatility ranges typical of compounds present in food samples. Tenax exhibits the most desirable retention characteristics. Careful selection of the experimental conditions lowers losses of volatile compounds by co‐evaporation with the solvent and allows a reliably quantitative analysis. Coefficients of variation of relative (normalized) peak areas and absolute peak area ratios of each compound to the standard are generally less th

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101104

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of the solute sample size on the measurement of temperature‐programmed retention indices (ITP) has been studied on glass capillary columns with different stationary phases, film thicknesses, and temperature programs. The sample capacity of a solute is little affected by the parameters of temperature program,i. e.initial temperature and heating rate. However, it has been found that in a temperature programmed run, allowable sample sizes for high ITPvalues are lower than for low ITPvalues. About 10 ng of each compound is recommended as the sample size for accurate measurement of ITPvalues on commonly used capillary column

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101105

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe optimized HPTLC of ginsenosides reported in this paper shows that the recommended solvent system has a higher resolution, greater spot capacity, and better reproducibility by comparison with the established ones in the previous literature. Detection and scanning in the fluorescence mode after visualization with 5% sulfuric acid/EtOH by the dipping technique improved and enhanced the sensitivity by a factor of nine compared to the commonly used absorbance made.Sample pretreatment by an adsorption clean‐up step on a small alumina column followed by 1‐butanol extraction instead of only a butanol‐extraction step made the chromatogram clearer, caused less background contamination, and reduced the tailing of some ginsenosides spots.The ‘peak grouping’ method was effectively used in HPTLC fingerprint identification of various commercial ginseng medicines and the chromatograms of roots of ginseng (white and red; Panax ginseng), American ginseng (P. quinquifolium), and sanchi (P. notoginseng) obtained under recommended condition are perfectly rec

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101106

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101107

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101108

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101109

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101110

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

年代:1987

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240101111

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

年代:1987

数据来源: WILEY