Determination of ronidazole in animal feeds by gas-liquid chromatography: a collaborative study by the EEC committee of experts

Abstract

A previously published gas-liquid chromatographic procedure with flame-ionisation detection for the determination of ronidazole in feeding stuffs has been investigated by inter-laboratory studies and with minor modifications has been recommended as a method for use by the EEC. Collaborative studies have shown the method to be acceptable for enforcement purposes. The ronidazole is extracted from the feeding stuff with ethyl acetate and the solution is cleaned up by transferring the ronidazole, as its hydrochloride, into an aqueous solution, liberating the ronidazole by making the solution alkaline and re-extracting with ethyl acetate. The solvent is then evaporated, the ronidazole converted into a volatile silyl derivative by reaction with NO-bis(trimethylsilyl)acetamide in hot quinoline solution and the reaction mixture, with the addition of diethyl phthalate as internal standard, is then examined by gas-liquid chromatography.