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 five chloro-, three methoxy- and five alkylthio-s-triazines, were investigated in micellar electrokinetic chromatography (MEKC) using a cationic surfactant. In this study, tetradecyltrimethyl ammonium bromide (TTAB) was selected as a cationic surfactant. The results indicate that the selectivity of neutral species of s-triazines in each class is not significantly influenced by buffer pH and micelle concentration, but the overall selectivity is considerably affected by these two separation parameters when charged solutes are present, particularly, at buffer pH below 5.0. Complete separation of thirteen 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 that 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 binding constants and P-ow (the partition coefficient of a solute between 1-octanol and water) reveals that the migration order of s-triazines in each class is primarily determined by the hydrophobicity of the solutes. (C) 1999 Elsevier Science B.V. All rights reserved.