Ion-selective electrodes in the analysis of drug substances: potentiometric microtitration of L-ascorbic acid with copper(II) sulfate and its application to the analysis of pharmaceutical preparations

A method for the determination of micro-amounts of L-ascorbic acid by direct potentiometric titration in aqueous buffered solution with 10 mmol dm^–3 copper(II) is described. The titration is carried out in a nitrogen atmosphere in the presence of SCN^– ions; the end-point is detected by using a copper(II) ion-selective electrode and a single-junction reference electrode. The method was successfully applied to the analysis of pharmaceutical preparations.