Enantioselective behaviour of ethylated γ-cyclodextrins as GC stationary phases for chlorinated pesticides and phase characterisation by HPLC

Small composition changes can influence the enantiomeric selectivity of alkylated cyclodextrins used as stationary phase in high resolution gas chromatography. A method is presented for the characterisation of such cyclodextrins using high performance liquid chromatography combined with evaporative light scattering and mass spectrometric detection (atmospheric pressure chemical ionisation in the positive ion mode). The method was applied to different batches of octakis (2,3,6-tri-O-ethyl)-γ-cyclodextrins (TEG-CD). Some showed a very good enantiomer selectivity for chlorinated pesticides. Separation evaluations were carried out with an improved test mixture containing selected, partly enantiomer enriched pesticides. Capillaries based on underethylated TEG-CD with up to 4 free OH groups dissolved in OV 1701-OH allowed the separation of α-HCH, o,p’-DDT, compounds of technical chlordane (cis-and trans-chlordane, U82, MC5, MC7, MC8) as well as chlordane metabolites (cis- and trans-heptachlor epoxide, oxychlordane) into enantiomers.