MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY WITH IN-SITU CHARGEDMICELLES .1. EVALUATION OF N-D-GLUCO-N-METHYLALKANAMIDE SURFACTANTS AS ANIONIC BORATE COMPLEXES

A series of N-D-gluco-N-methylalkanamide (MEGA) surfactants was evalua ted in micellar electrokinetic capillary chromatography (MECC) of neut ral and charged species. The nonionic MEGA surfactants are readily con verted in situ to anionic borate complexes through the association bet ween their polyhydroxy bead groups and borate ions at alkaline pH. The MEGA-borate complex surfactants yielded micelles with adjustable surf ace charge density, and consequently, the magnitude of the retention w indow was readily altered by the pH and the concentration of borate in the running electrolyte. Studies by B-11 NMR and liquid secondary ion mass spectrometry on the borate complex formation with MEGA surfactan ts permitted the quantitative and qualitative determination of the var ious MEGA-borate complexes, respectively, and allowed the comparison o f the MEGA-borate micelles to other in situ charged micelles recently introduced by this laboratory, i.e., the alkyl glucopyranoside-borate micelles. The bulky polyhydroxy head group of the MEGA-borate surfacta nts yielded MECC systems with unique retention properties toward neutr al and charged species. At constant micellized surfactant concentratio n, the methylene group selectivity of various homologous series, e.g., alkylbenzenes, phenylalkyl alcohols, and phenyl alkyl ketones, was la rgely unaffected by the length of the alkyl tail of the surfactant, in dicating a similar physicochemical basis for retention on the various MEGA-borate micellar phases. Also, when the micellized surfactant conc entration was held constant, the homologous solutes exhibited homoener getic retention with the various in situ charged micellar phases. Unde r the same conditions, the capacity factors of neutral solutes increas ed linearly with the alkyl chain length of the MEGA surfactants, indic ating an increase in the hydrophobic phase ratio of the MECC systems. The MEGA-borate micellar phases were useful in the separation of a num ber of herbicides, polyaromatics, barbiturates, and dansyl amino acids . In addition, in the presence of small amounts of gamma-cyclodextrin, the MEGA-borate micelles allowed for the high resolution chiral separ ation of D,L dansyl amino acids.