Simultaneous determination of dihydroxybenzenes, aminophenols and phenylenediamines in hair dyes by high-performance liquid chromatography on hypercross-linked polystyrene.

The retention of polar organic molecules such as dihydroxybenzenes, aminophenols and phenylenediamines on a 250 x 4.6 mm id column packed with 5 microns hypercross-linked polystyrene Chromalite 5HGN (Purolite) was studied. The influence of separation parameters such as concentration of acetonitrile, buffer (citrate, phosphate) concentration, ionic strength and pH of the eluent on their retention was investigated. Under optimum conditions [acetonitrile-0.3 mol l-1 ammonium phosphate, pH 5.15 (30:70 v/v)], eight substances generally used as dye intermediates in hair colouring compositions could be separated within 20 min. An HPLC method with spectrophotometric detection is proposed for the simultaneous determination of pyrocatechol, resorcinol, hydroquinone, o-, m- and p-aminophenols and p-phenylenediamine in commercial haircolour products. The detection limits of these compounds are in the range 0.05-0.16 microgram ml-1. The suitability of the method is demonstrated by the analysis of three different permanent hair dyes.