Separation ability and stoichiometry of cyclodextrin complexes

Gas-liquid chromatography has been applied to search relations between selectivity towards isomers and stoichiometry of cyclodextrin complexes. The model tested compounds were: dimethylnaphthalenes and alpha- and beta -pinenes as constitutional isomers; cis/trans decalins, anetholes and isosafroles as diastereomers and as enantiomers (+/-)-alpha -pinenes and (+/-)camphenes. Experimental retention data are used to confirm a simple theoretical model that allows distinguishing formation of G . CD complexes (1:1) and G . CD2 complexes (1.2), Based on the experimental data, stability constants K were evaluated. It has been found that remarkable selectivity factor ct may appear both within the range of 1:1 stoichiometry (P-CD complexes of decalins and of alpha- and beta -pinenes) and 1:2 stoichiometry (alpha -CD complexes with (+/-)-alpha -pinenes and (+/-)-camphenes), Occasionally selectivity arises from a different composition, when one isomer forms a 1:1 stoichiometry complex while another Forms a 1:2 complex (dimethylnaphthalenes, cis/trans-anetholes and cis/trans-isosafroles). (C) 2000 Elsevier Science B.V. All rights reserved.