Determination of (+/−) Elution Orders of Chiral Organochlorines by Liquid Chromatography with a Chiral Detector and by Enantioselective Gas Chromatography

Abstract

Enantioselective gas chromatography (GC) with 5 modified cyclodextrins was applied to chiral organochlorines. A prerequisite for determining GC elution orders of enantiomers is the availability of enantioenriched standard solutions. In addition to compounds reported before (e.g., α-HCH, PCB 174, oxychlordane), we determined the sign of optical rotation of enantioenriched solutions of e-aeee-pentachlorocyclohexene-1 (β-PCCH), perdeuterated α-HCH (α-PDHCH), perdeuterated β-PCCH, and the persistent compound of technical toxaphene—2-exo,3-endo,5-exo,9,9,10,10-heptachlorobornane (B7-1453)—by liquid chromatography (LC) with a chiral detector. An enantioenriched solution of (β-PCCH was obtained by enantioselective degradation of α-HCH with (-)-brucine. In addition to forming an enantiomeric excess of (-)-α- HCH, we formed enantioenriched (+)-(α-PCCH. In a similar study, α-PDHCH showed the same behavior with respect to enantioselectivity. Dextrorotation of an enantioenriched solution of B7-1453 was also confirmed by LC with a chiral detector. Enantioseparation of chiral organochlorines on 5 chiral stationary phases resulted in several reversed elution orders. These results indicate that a careful check of elution orders of organochlorine enantiomers is necessary prior to comparison of literature data for the study of enantioselective processes in the environment.

Production of Toxaphene Enantiomers by Enantioselective HPLC after Isolation of the Compounds from an Anaerobically Degraded Technical Mixture

“…Therefore, the ChiraDex column was not suitable for solving this problem. Establishing the optical rotation of the enantiomers has to be performed by injection of pure enantiomers into a system consisting of a nonchiral stationary phase and a chiral detector (11). Nonchiral stationary HPLC phases give sharper peaks that may provide the necessary sensitivity for chiral detectors.…”

“…However, an objective interpretation of enantioselective data requires enantioenriched (or enantiopure) standards since reversals of the GC elution orders have been reported for organochlorine enantiomers ( , ). Nonracemic standards can be produced with the help of enantioselective HPLC (eHPLC) ( − ). In the case of compounds of technical toxaphene (CTTs) this has not been achieved before.…”

Gas Chromatographic Enantiomer Separation of Atropisomeric PCBs Using Modified Cyclodextrins as Chiral Phases

“…Injection of 1 lL aliquots of the standard solutions were made in the splitless mode (2 min splitless) and the temperature of the oven was then programmed. [11,40]. It was suggested that one group of the synthesis products of TBDMS-b-CD elutes (+)-a-HCH in front of ( -)-a-HCH and one group elutes the ( -)-a-HCH first.…”

“…Vetter and coworkers used heptakis(2,3,6-tri-O-tert-butyldimethylsilyl)b-cyclodextrin (TBDMS-b-CD), synthesized according to Blum and Aichholz [10], as chiral selector. It was considered that this phase was indispensable for enantioselective analysis of chiral organochlorines [11]. However, a severe problem with this selector is that it cannot be synthesized in a reproducible manner [12].…”

“…Published in Journal of High Resolution Chromatography 23, issue11,[619][620][621][622][623][624][625][626][627] 2000 which should be used for any reference to this work…”