Analysis of reactions of aromatic anions with quaternary ammonium ions in ion association-nonionic micellar electrokinetic chromatography

Reactions in ion association-nonionic micellar electrokinetic chromatograph y have been analyzed using mobility change in capillary electrophoresis. Se veral quaternary ammonium ions and aromatic anions were used as pairing cat ions and anions, respectively, and three kinds of nonionic surfactant were used to form micelles in an aqueous solution. The apparent electrophoretic mobility of the analyte anions decreased with increasing concentrations of nonionic surfactant and/or pairing cation. The equilibrium reactions partic ipating in this electrophoresis system are binding of anions to nonionic su rfactant micelle (K-B), ion association of anions with pairing cation (K-as s), and distribution of the formed ion associates to the nonionic surfactan t micelle (K-B,K-IA) The equilibrium constants were determined by non-linea r least-squares analyses by applying the analyses to the mobility decreases . Equilibrium constants of K-b and K-B,K-IA for monovalent anions were foun d to be larger than those for divalent anions, and K-B,K-IA values for each anions were larger than their K-B values. The results obtained can be expl ained from distribution phenomena of analytes between aqueous and organic p hases.