ANALYSIS OF BASIC HAIR-DYES BY HPLC WITH ONLINE POSTCOLUMN PHOTOCHEMICAL DERIVATIZATION

A reversed phase liquid chromatographic method is proposed for the ana lysis of basic hair dyes (raw materials and colourant formulations). T he performance of the method was enhanced by introducing postcolumn on -line photochemical derivatisation in combination with a Diode Array D etector. On-line photoderivatisation provided an effective way of sele ctively transforming the analytes to compounds with different spectral properties. For each analyte two characteristic UV-Visible spectra (p hotoreactor on and off) were obtained with the same mobile phase and t his information in combination with the chromatographic data (k' at pH 3.0 and 4.5) enabled the unambiguous identification of both commonly used, approved, and banned basic hair dyes. Additionally, this approac h was found useful to improve the method sensitivity, allowing the det ermination of analytes present in low concentration (0.03 %) in comple x commercial formulations.