REVERSED-PHASE LIQUID-CHROMATOGRAPHIC MEASUREMENT OF THE INFLUENCE OFA CO-MODIFIER FUNCTIONAL-GROUP ON THE RETENTION BEHAVIOR OF THE BETA-CYCLODEXTRIN PYRENE COMPLEX

Reversed-phase liquid chromatography was used to determine the stoichi ometry and formation constants of the complex of beta-cyclodextrin wit h pyrene in the presence of several secondary modifiers in a 59% (v/v) methanol in water mobile phase. All secondary modifiers contained a b ulky and hydrophobic tert.-butyl moiety attached to functional groups of varying polarity and heteroatom composition. Although pyrene exhibi ts no interaction with beta-cyclodextrin in a 59% (v/v) methanol in wa ter solvent alone, the addition of a co-modifier resulted in dramatica lly short retention times. The stoichiometry of the beta-cyclodextrin- pyrene was determined to be predominantly 2:1. Formation constants wer e estimated to be approximately 10(4) M-2. Adding functionality and in creasing chain length in co-modifiers resulted in a corresponding enha ncement of formation constants and reduction of capacity factors. The effects of pH on the equilibrium and the applications of co-modifier e ffects in environmental analysis are discussed.