Analysis of semipermanent hair dyes by HPLC with on-line post-column photochemical derivatisation.

The development of a selective and sensitive HPLC method for the determination of semipermanent hair colorants in cosmetic formulations is proposed. The separation and identification of N-hydroxyalkyl nitrophenylenediamines and nitroaminophenols were performed by HPLC with on-line, post-column, photochemical derivatisation, using a reversed phase, ion-pair system with 1,8-diaminooctane and heptansulfonate in the mobile phase. Two UV spectra (photoreactor on and off) were obtained for each analyte, adding information for confirming peak identity. Analyte-modified spectral properties were used to increase the method sensitivity. The proposed method was successfully applied to quality control and stability studies of cosmetic formulations. [ABSTRACT FROM AUTHOR]