Traces of organic acids can be determined only with difficulty in the presence of high concentrations of standard anions, because their small peaks generally disappear under the larger peaks of the standard anions. A simple dose-in-gradient improves the separation: acetate and formate are baseline-separated from fluoride. Furthermore, oxalate elutes considerably less than sulfate. The separation takes place on a column of the Metrosep A Supp 7 - 250/4.0 type with subsequent conductivity detection following sequential suppression.