Enzyme immunoassay for the detection of trimethoprim in raw milk

Trimethoprim (TMP) is mostly used in combination with different sulfonamides for the treatment of bacterial infections. In milk a maximum residue limit (MRL) for TMP is fixed at 50 mu g/kg. An ELISA was developed for the determination of TMP in raw milk. Antibodies with a high specificity were raised in rabbits. The ELISA was carried out as an indirect competitive antibody-capture test with a detection limit of 12.5 mu g/kg. Quantification is possible up to 100 mu g/kg without sample dilution. The immunoassay described is suitable as a screening method for the detection of TMP at the MRL and fulfils the requirements of the EU-Regulation 281/96.