Determination of 4-chloroaniline and 4-chlorophehyl urea in honey by liquid chromatography with electrochemical detection

A liquid chromatographic technique with amperometric detection was developed for determining diflubenzuron metabolites, 4-chlorophenyl urea and 4-chloroaniline, using a Spherisorb C-18 column 5 mu m (4.1 x 250 mm). A mobile phase of acetonitrile / citrate-disodium hydrogenphosphate buffer, 30:70, at pH=7.0, was pumped at a flow rate of 1 mL min(-1). The amperometric detector, equipped with a glassy carbon working electrode was operated at 1100 mV vs Ag/AgCl. The method showed a limit of detection of 0.46 mu g 1(-1) for 4-chlorophenyl urea and 0.20 mu g 1(-1) for 4-chloroaniline. Reproducibility in terms of relative standard deviation ranged between 1.24 and 4.50 % for the 4-chlorophenyl urea and 1.60 and 3.93% for the 4-chloroaniline. The method was applied to the determination of both metabolites in honey. The prior extraction of the two substances from honey was established using different solid-liquid extraction phases.