Migration behavior and separation of s-triazines in micellar electrokinetic capillary chromatography using a cationic surfactant

The migration behavior and separation of various s-triazines, including fiv e chloro-, three methoxy- and five alkylthio-s-triazines, were investigated in micellar electrokinetic chromatography (MEKC) using a cationic surfacta nt. In this study, tetradecyltrimethyl ammonium bromide (TTAB) was selected as a cationic surfactant. The results indicate that the selectivity of neu tral species of s-triazines in each class is not significantly influenced b y buffer pH and micelle concentration, but the overall selectivity is consi derably affected by these two separation parameters when charged solutes ar e present, particularly, at buffer pH below 5.0. Complete separation of thi rteen s-triazines was optimally achieved within 6 min on addition of TTAB ( 15 mM) to a phosphate buffer (70 mM) at pH 4.75 or 3.8. Based on a model th at describes the relationship of the effective electrophoretic mobility of a neutral solute and micelle concentration in MEKC, the migration behavior of chloro-s-triazines at pH 6.0 is predicted and the binding constants of s -triazines to TTAB micelles are evaluated. The correlation between the bind ing constants and P-ow (the partition coefficient of a solute between 1-oct anol and water) reveals that the migration order of s-triazines in each cla ss is primarily determined by the hydrophobicity of the solutes. (C) 1999 E lsevier Science B.V. All rights reserved.