Multiclass screening method to detect more than fifty banned substances in bovine bile and urine.

A multiclass screening method to detect fifty-three forbidden substances by liquid-chromatography coupled to hybrid high-resolution mass spectrometry (LC-Q-Orbitrap) was developed and validated in bovine bile and urine. Eight classes of compounds were included in the method's scope (β-agonists, corticosteroids, nitroimidazoles, progestins, resorcylic acid lactones (RALs), sedatives, steroids and stilbenes) plus chloramphenicol and dapsone. After hydrolysis, the sample was divided in two aliquots, which followed two parallel purification steps. The reunified extracts were injected and two chromatographic runs performed in positive and negative ionization mode, respectively. The validation data (60 different samples per matrix) proved that the method was fit for purpose with detection capabilities lower than 1 μg L-1 in both matrices. The combined application of accurate mass acquisition and two-stage mass spectrometry (parallel reaction monitoring) was crucial to achieve suitable selectivity, which is the most critical parameter mainly for urines. Finally, the long-standing problem of the high rate of false positive results for RALs, due to the natural ingestion of mycotoxin, zearalenone, was taken on including all their labelled standards. That allowed a very satisfactory management of this screening test.