STUDIES ON THE DETERMINATION OF INORGANIC ANIONS BY CAPILLARY ELECTROPHORESIS

In order to separate anions effectively it is usually necessary to eliminate or reverse the direction of electroosmotic flow (EOF) resulting from attraction of cations to the negatively charged surface of a silica capillary. Previous workers have accomplished this by adding a quaternary ammonium salt (Q(+)) as an EOF ''modifier''. Under typical experimental conditions, a concentration of Q(+) > 0.25 mM is required to reverse the EOF direction. Addition of a low percentage of 1-butanol to the aqueous electrolyte was found to reduce the EOF. A combination of butanol and a very low concentration of Q(+) (typically 0.03 mM) was found to be particularly effective in controlling EOF and in giving effective separations of complex mixtures of anions. The probable mechanism of the butanol-Q(+) effect is discussed.