Differential-pulse polarographic determination of synthetic colouring matters in drugs and cosmetics

Abstract

Differential-pulse polarographic peak potentials of sixteen food and three cosmetic synthetic colouring matters were determined at several pH values. With a few exceptions very similar peak potentials were obtained, making the polarographic identification of the dyes difficult. For this reason a systematic study of the effect of tetraphenylphosphonium chloride (TPPC) on the polarographic behaviour of the dyes was undertaken and, in some instances, noticeable modifications of the peak potentials and peak currents were observed, allowing a better identification and determination of the colouring matters. Procedures for applying the results to the determination of the dyes in drugs and in cosmetics were developed.