Consequences of variable purity of heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin determined by liquid chromatography–mass spectrometry on the enantioselective separation of polychlorinated compounds

Abstract The composition of 10 batches of heptakis(2,3,6-tri- O -methyl)-β-cyclodextrin (PM-CD) from different suppliers was determined by high-performance liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometry (MS). Considerable differences were found. Some batches consisted of more than 95% pure PM-CD, whereas others were not completely derivatised or contained a significant amount of by-products. Some suggestions about the structures of these impurities are given though neither nuclear magnetic resonance spectroscopy nor MS–MS investigations could completely reveal their nature. Capillaries for high-resolution gas chromatography were coated with the batches of most differing composition. They demonstrated widely varying column performance and separation properties for selected chiral polychlorinated substances such as chlordane compounds, o , p ′-DDT, o , p ′-DDD, α-hexachlorocyclohexane and atropisomeric polychlorinated biphenyls. The best enantioselectivity was obtained with the purest PM-CD. Compared to separations reported in the literature, a broader enantioselectivity was observed and also trans -heptachlor epoxide and oxychlordane could be resolved into enantiomers.