Determination of zinc pyrithione in cosmetic products by high-performance liquid chromatography with pre-labelling.

A high-performance liquid chromatographic (HPLC) method has been developed for the determination of zinc pyrithione (Zpt) in commercial cosmetic products. Zpt was pre-labelled with N-dansylaziridine and determined by reversed-phase HPLC. Ingredients in cosmetic products did not interfere in the pre-labelling reaction. The calibration graph for Zpt was linear in the range 1.4-66 ng. The coefficient of variation was 0.9% for 17-ng injections. Using the proposed method, Zpt in commercial cosmetic products was determined with high sensitivity and high selectivity. The proposed method is also applicable to the determination of trace amounts of Zpt adsorbed on human hair.