Published:Journal of Chromatographic Science, ISSN 0021-9665 Volume 44, Number 10, November/December 2006, pp.596-601

Enantioseparation of Chiral Organochlorines on Permethylated b- and g-Cyclodextrin, as well as 1:1 Mixtures of Them

Walter Vetter[1], Katja Lehnert[1], and Georg Hottinger[2]
[1]Universität Hohenheim, Institut für Lebensmittelchemie, D-70593 Stuttgart, Germany and
[2]BGB Analytik KG, Lettenstrasse 97, CH-8134 Adliswil, Switzerland

Gas chromatography columns coated with 10% permethylated b- and g-cyclodextrin in 85% dimethyl–15% diphenyl polysiloxane (b- and g-PMCD, respectively) and 1:1 mixures are prepared and tested with regard to the enantioseparation of chiral chloropesticides. On the columns with the individual O-methylated cyclodextrins (O-tCDs), the enantiomers of aaeeee-hexachlorocyclohexane (a-HCH), e-aeee-1,3,4,5,6-pentachlorocyclohex-1-ene (b-PCCH), and e-aaee-1,3,4,5,6-pentachlorocyclohex-1-ene (g-PCCH), cis- and trans-chlordane, and cis-heptachlor epoxide are separated on both columns, with the exception of the latter being separated only on b-PMCD. On the column coated with 5% b- and 5% g-PMCD, the resulting separation factor (a) is virtually 1/2 of the arithmetric mean of the elution-dependent separation factors on the individual O-tCDs. In case of reversed elution order on b- and g-PMCD, the enantiomers are not resolved on the mixed columns as is the case with cis-chlordane. Likewise, the lower resolution of the g-PCCH enantiomers on the mixed columns prove the reversed elution order on b- and g-PMCD without having enantioenriched standards available. On the column coated with 5% b- and 5% g-PMCD, similar retention times to those observed on both 10% b-PMCD and 10% g-PMCD are obtained. On the column coated with 10% b- and 10% g-PMCD, significantly longer retention times are obtained compared with the columns that contain a total of 10% chiral stationary phase (CSP). This indicates that a relevant part of the interaction of the analytes with the chiral selector is non-enantioselective and, thus, only delays the elution of both enantiomers. Moreover, these non-enantioselective interactions prevent a direct comparison of CSPs with different amounts of the chiral selector. However, this is possible by using mixed phases of two CSPs with similar properties. Using this system, it is demonstrated that for the organochlorine compounds studied, no higher separation factor is observed on the mixed CSPs than on the individual O-tCD with the higher separation factor. Estimations allow a prediction that enantioseparations of organohalogen compounds can be achieved on columns coated with as little as 1% of the CSP.

Reproduction of editorial content of this journal is prohibited without publisher’s permission.

Site Map: Home | Current Issue | Subscribe | Back Issues | About Us | Meetings | Advertising |
| Books for Sale | For the Author | Links | Supplier Info | Search |