Effects of blending bare-silica and reversed-phase on retention of neutralcompounds in capillary electrochromatography

Most commercially available instruments for capillary electrochromatography (CEC) have a fixed configuration and lack the flexibility to use shorter c olumns. Applying a blended stationary phase (a phase consisting of a given ratio of bare silica and reversed phase material) can simulate columns of d ifferent length in CEC, The goal of this work was to examine the effect of the degree of blending of reversed-phase columns (with bare silica) on the speed of the separation of neutral compounds in CEC. Optimum column packing mixture was determined from the variation of the solute retention factors as a function of the ratios of blending of reversed-phase and bare silica. By adjusting the column composition, solute retention factors and the analy sis run time were halved when compared to a pure reversed-phase column of t he same length. Stationary phase blending can be considered as an additiona l parameter to mobile phase variation, column temperature and applied elect ric field for the optimization of selectivity and analysis time. By adjusti ng the stationary phase composition, mobile phase composition, column tempe rature and applied electric field, the analysis run time of neutral compone nts was decreased more than 75% when compared to a separation obtained on n eat reversed-phase column of the same dimensions. The linear dependence of the retention factors as a function of the blend ratio (reversed phase/bare silica) offers a framework for designing a "blended" packed capillary colu mn for CEC separations.