Separation on a ODS reversed-phase column with acetonitrile-0.1% phosphoric acid (65 + 35) as mobile phase provides a simple and rapid method for the determination of undecenoic acid in dermatological preparations. Common preservatives, bactericides and antiseptics do not interfere. Tolnaftate was employed as the internal standard throughout the assay. A linear relationship was established between the peak-area ratio of undecenoic acid to the internal standard and concentration of undecenoic acid over the range 0.01-0.1 ng ml-1. © 1990.
