DETECTION OF STREPTOMYCINS IN RAW-MILK BY AN ANTIBODY-CAPTURE IMMUNOASSAY

An indirect competitive enzyme-linked immunosorbent assay carried out as an antibody-capture test was developed for the determination of streptomycins in milk. The antiserum was raised in rabbits using streptomycin linked to a bacterial protein as immunogen. The antibodies were concentrated by threefold ammonium sulphate precipitation and reacted equally with streptomycin and dihydrostreptomycin. No other cross-reactions were observed. To perform the test microtitre plates were coated overnight with streptomycin (I mg ml-1). The milk to be examined was skimmed and treated with oxalic acid. Antiserum and milk samples were mixed and incubated for 1 h. Depending on the amount of streptomycin or dihydrostreptomycin in the sample, more or less antibody molecules remain free to be bound to the streptomycin coat. The sensitivity of the test is better than 1.6 ug kg-1. Quantification is possible up to 100 mug kg-1 without sample dilution.