Combined high-performance liquid chromatography and radioimmunoassay for the screening of 19-nortestosterone and methyltestosterone residues in meat samples

A procedure is described for the detection of 17 beta-19-nortestosterone (17 beta-19-NT) and 17 alpha-methyltestosterone (17 alpha-MT) in muscle tissue by a combination of high-performance liquid chromatography and radioimmunoassay. The steroids were released from the muscle tissue by enzyme digestion, and the extracts were purified by solid-phase extraction. A meat sample from the retail trade, which was proved to contain 17 beta-19-NT and 17 alpha-MT residues by gas chromatography-mass spectrometry, and blank meat samples obtained from non-treated experimental animals were purified and the extracts injected into the liquid chromatograph. With an automatic fraction collector, fifteen fractions of 1 ml each were obtained, which after evaporation were subjected to a radioimmunoassay for the steroid concerned. It was demonstrated that none of the fractions from the blank meat samples contains any substance that interfered with the immunochemical detection system. In addition, a good qualitative agreement between the two sets of results was obtained. Although the sample preparation step is rather labour-intensive, the method can be successfully applied as a reliable confirmation method for positive radioimmunoassay screening results in circumstances where no gas chromatography-mass spectrometry facilities are available.