SummaryOptimization of a CE method with indirect UV detection for speciation of suJfur-containing anions is described. Sensitivity, selectivity, and separation using a chromate background electrolyte (the electrolyte most often used for inorganic anions) and a pyromelhtate electrolyte are compared. The pyromellitate electrolyte is recommended because its use results in better sensitivity for the ions analyzed. The composition of the electrolyte was 2.25 mM pyromellitic acid, 6.5 mM NaOH, 0.75 mM hexamethonium hydroxide, and 1.6 mM triethanolamine, pH 10. Separation of seven sulfur-containing anions with indirect detection at 254 nm was achieved in one run in less than 7 min.