High Performance Liquid Chromatographic Studies of Some Cyclodextrin Complexes

Abstract

AbstractThe complex formation between β‐cyclodextrin and nitrophenol isomers was studied with the aid of reversed phase liquid chromatography. The effects of temperature, pH, and methanol content on the formation constants of the nitrophenol/β‐cyclodextrin complexes were investigated. The complex formation constants were found to decrease with increasing temperatures. This decrease in formation constant was independent of the pH of the mobile phase. From the temperature dependence of the formation constants we were able to extract enthalpies and entropies of the complex formation. The values calculated in this work agree favorably with published values. Three pHs were examined: 3.57, 4.65, and 5.6. The formation constants of the ortho and meta isomers were highest at the lowest pH and leveled off at the two higher pHs. The para isomer showed a minimum in the formation constant at pH 4.65. This behavior was independent of the pH of the mobile phase.