Determination of amprolium in egg yolk and muscle tissue (chicken) by HPLC with post-column reaction and fluorometric detection, using on-line sample clean-up and pre-concentration steps.

A continuous flow system was coupled to a high-pressure liquid chromatography (HPLC) system, resulting in an automated system for the determination of amprolium in egg yolk and (chicken) muscle tissue. The sample was diluted (yolk) or extracted (tissue) with water, and the solution obtained was dialysed against water as the recipient stream. Aliquots of the dialysed solutions were pumped onto a short pre-concentration column. By means of the mobile phase, the concentrate was back-flushed onto the analytical column and amprolium was separated from interfering substances, using a reversed phase ion-pair system. Amprolium was post-column oxidized to amprochrome, which was detected fluorometrically. Linear calibration curves for both yolk an muscle tissue were obtained in the 10-250 micrograms/kg range. The detection limit is approximately 3 micrograms/kg. This method was applied to eggs and muscle tissue, which were commercial obtained. Egg yolk was found to be frequently contaminated with low levels of amprolium (29.4% positive of 266 samples investigated; mean concentration of positive samples = 58 micrograms/kg), whereas only a few muscle samples contained detectable levels (4.9% positive of 81 samples investigated; mean concentration of positive samples = 5 micrograms/kg).