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

The composition of 10 batches of heptakis(2,3,6-tri-O-methyl)-beta -cyclode xtrin (PM-CD) from different suppliers was determined by high-performance l iquid 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 d erivatised or contained a significant amount of by-products. Some suggestio ns about the structures of these impurities are given though neither nuclea r magnetic resonance spectroscopy nor MS-MS investigations could completely reveal their nature. Capillaries for high-resolution gas chromatography we re coated with the batches of most differing composition. They demonstrated widely varying column performance and separation properties for selected c hiral polychlorinated substances such as chlordane compounds, o,p'-DDT, o,p '-DDD, alpha -hexachlorocyclohexane and atropisomeric polychlorinated biphe nyls. The best enantioselectivity was obtained with the purest PM-Co. Compa red to separations reported in the literature, a broader enantioselectivity was observed and also trans-heptachlor epoxide and oxychlordane could be r esolved into enantiomers. (C) 2001 Elsevier Science B.V. All rights reserve d.