COMPARISON OF BIOSENSOR, MICROBIOLOGICAL, IMMUNOCHEMICAL, AND PHYSICAL METHODS FOR DETECTION OF SULFAMETHAZINE RESIDUES IN RAW-MILK

A biosensor assay based on biospecific interaction analysis (BIA) was compared with already existing methods for detection of sulphamethazin e (SMZ) residues in milk. Microbial inhibitor and receptor assays, an enzyme-linked immunosorbent assay (ELISA), high-pressure Liquid chroma tography (HPLC), and BIA were used to analyze milk samples from SMZ-tr eated cows. The results of the commercially available tests (Delvotest SP Special, BR-test Blue Star, Charm II test) were in agreement with the claimed sensitivity of the respective assays. The agreement betwee n the quantitative methods (ELISA, HPLC, BIA) varied. The microbial in hibitor assays and BIA were also used to screen 330 tanker milk sample s. All samples were negative in the inhibitor tests, whereas the BIA i ndicated the occurrence of less than 0.9 mu g of SMZ per kg of milk in 5 samples and 1.5 +/- 0.6 mu g/kg in one sample. HPLC indicated the p resence of SMZ in the latter sample, although the concentration was be low the detection limit of the method. The advantages offered by the B IA: no sample preparation, high sensitivity, and rapid, fully automate d analysis in real time make the technology an interesting alternative to existing screening methods within future food-quality control syst ems.