Capillary electrophoresis of carboxylated carbohydrates. IV. Adjusting the separation selectivity of derivatized carboxylated carbohydrates by controlling the electrolyte ionic strength at subambient temperature and in the absence of electroosmotic flow.

The effect of the ionic strength of the running electrolyte on selectivity and resolution of 7-aminonaphthalene-1,3-disulfonic acid (ANDSA) derivatives of carboxylated monosaccharides and sialooligosaccharides derived from gangliosides was evaluated in capillary electrophoresis in the absence of electroosmotic flow and at subambient temperature. The acidic saccharides used in this study were derivatized with ANDSA fluorescing tag to facilitate their detection by laser-induced fluorescence. To maximize resolution among the derivatized saccharides, commercially available fused-silica capillaries with 'zero' electroosmotic flow having polyvinyl alcohol coating on their inner walls were used as the separation capillaries. The effective electrophoretic mobility (mu) of the various ANDSA derivatized mono- and oligosaccharides decreased linearly with the inverse of the square root of the buffer concentration (1/square root of C) used in the running electrolyte. The extent of screening of the charge on the solute by the electrolyte counterions varied among the various saccharides as was manifested by the slopes of the lines of mu vs. 1/square root of C. Increasing the ionic strength of the running electrolyte allowed, via its charge screening effect, the modulation of selectivity thus adjusting the resolution of closely related saccharides.