Preparation of quality control materials for the determination of sulfonamides in animal feed

A feasibility study of the preparation of quality control materials for the analysis of medicated feeds has been carried out. Two analytical methodologies for the analysis of sulfonamides in feeds were developed, validated and applied to homogeneity and stability studies. Pig feeds spiked with sulfadiazine and sulfadimidine were prepared. The drugs were spiked at 500 µg g^?1, representing what can be expected in a commercial medicated feed, and at 2 and 5 µg g^?1, which roughly correspond to drug-free feeds cross-contaminated during the fabrication process. The homogeneity of both the bulk and the bottled materials was verified. A stability study of the materials containing 2 and 5 µg g^?1 of sulfonamides was carried out over an 18-month period at room temperature, at 4°C and ?20°C. The determination of sulfadiazine and sulfadimidine in samples coming from these homogeneity and stability studies of the quality control materials was carried out by high-performance liquid chromatography (HPLC) with either ultraviolet light or fluorimetric detection, depending on the concentration of the analytes in the samples.