Determination of p-phenylenediamine and its metabolites MAPPD and DAPPD in biological samples using HPLC-DAD and amperometric detection.

A sensitive and selective HPLC method using a diode array detector (DAD) and an electrochemical detector (ECD) in series has been developed and validated for the quantitative measurement of p-phenylenediamine and its acetylated metabolites N-acetyl-p-phenylenediamine (MAPPD) and N,N'-diacetyl-p-phenylenediamine (DAPPD) in biological samples. The separation was carried out on a hydrophilic modified AQUA C(18) column and the mobile phase was composed of acetonitrile: ammonium acetate solution (5:95, 25 mM, v/v). Spectrophotometric detection was performed at 240 or 255 nm and amperometric detection was carried out using a positive oxidation potential of 400 mV. The quantification of the three analytes was validated in the range of 0.05-50 microM and the established limits of determination were 0.5 microM for PPD and MAPPD and 1 microM for DAPPD. The standard deviations (N=9) were lower than 7.5% at a concentration of 1 microM. The samples were stabilised with ascorbic acid to prevent PPD from oxidizing. Pretreatment of samples or analyte enrichment before sample injection is not required. The method proved to be accurate, sensitive and sufficiently specific. It was applied to the ecotoxicological study of the kinetics of the PPD N-acetylation in cell lysates in two different media.