Simultaneous determination of methylparaben, propylparaben and thimerosal by high-performance liquid chromatography and electrochemical detection.

A reversed-phase high-performance liquid chromatographic method using amperometric detection has been developed for the analysis of methylparaben, propylparaben and thimerosal. The liquid chromatographic separation of the three preservatives was made possible on a C18-bonded silica column with a mixed solvent consisting of methanol and aqueous 0.02 M phosphoric acid (59:41, v/v). A potential value of +1.25 V versus Ag/AgCl was chosen for simultaneous analysis. The limits of detection were 1, 2 and 5 ng for a 20 microliters injection volume of methylparaben, propylparaben and thimerosal, respectively. The analysis time of less than 20 min in this study was found to be applicable for routine analysis of these compounds in pharmaceutical products.