SIMPLIFIED DETERMINATION OF SULFONAMIDES RESIDUES IN MILK, MEAT AND EGGS

This paper describes a simple procedure for the determination of 13 sulfonamides by HPTLC and 11 by HPLC in milk, meat and eggs. After extraction with dichloromethane, the fat is removed over a silica cartridge, the sulfonamides are eluted with a buffer solution and the eluate is extracted with ethyl acetate. This solution is divided in two portions: one is concentrated and analysed by HPLC with a diode array or UV detector at 266 nm on a C18 column and the other portion is analysed by HPTLC on silica plates. Using this procedure, it is possible to analyse 12 samples a day with a detection limit of 2-mu-g/kg by HPLC and 10-mu-g/kg by HPTLC. Upon analysing 105 samples of pork meat bought in shops in the Lake of Geneva region, the number of positive samples proved surprisingly high (79%). Moreover, 23 percent of the samples had sulfamethazine levels over the legal limit of 100-mu-g/kg. We also analysed 98 meat samples from various European suppliers. Forty-seven were positive for sulfamethazine, whereas occasionally also low levels of sulfamethoxypyridazine, sulfadoxine, and sulfamethoxazole were encountered. Seven samples contained excessive residues. No sulfonamide residues were detected in milk, eggs and their derived products. The method was successfully tested by four laboratories on three pork meats containing low, medium and high amounts of sulfamethazine.