RAPID ENZYME IMMUNOASSAYS FOR THE DETECTION OF 3 SULFONAMIDES IN MILK

Two rapid competitive enzyme immunoassays, utilizing test strip and im munofiltration techniques, for the detection of three sulphonamides (s ulphadiazine, sulphamethazine and sulphamethoxypyridazine) in milk wer e developed. In these direct immunoassays, free sulphonamide competed with the relevant sulphonamide-horseradish peroxidase conjugate for th e binding sites of membrane-bound polyclonal antibodies. Test strips w ere incubated in the sample solution containing the sulphonamide-enzym e conjugate, while, for the immunofiltration assays, sample and enzyme conjugate solutions were added consecutively. After incubation of enz yme substrate/chromogen solution, the colour reaction was evaluated vi sually by observing the difference to the negative control. The detect ion limits for each of the three compounds were between 5 and 10 ng ml (-1) of milk using the test strip assays and between 10 and 20 ng ml(- 1) of milk using the immunofiltration assays.