Screening for estrogen residues in calf urine: comparison of a validated yeast estrogen bioassay and gas chromatography tandem mass spectrometry
Résumé
Within the European Union the control for residues of illegal hormones in food producing animals is based on urine analysis for a few target analytes using gas chromatography mass spectrometry and/or liquid chromatography tandem mass spectrometry. Recently, we developed a robust yeast bioassay screening tool for estrogens which was validated as a qualitative screening method in accordance with EC decision 2002/657/EC. In this study we present long-term performance data and a comparison of urine data as obtained with this bioassay, and data from an established gas chromatography tandem mass spectrometry (GC/MS/MS) confirmatory analysis method. More than 120 calf urine samples from a controlled reference experiment were analysed using both protocols. According to the GC/MS/MS method only the natural estrogens 17τ-estradiol and estrone were present in the non-compliant samples. The bioassay was less sensitive than GC/MS/MS for the relatively weak estrogenic compound 17τ-estradiol, in accordance with expectations. Assuming that application of the mass spectrometric method is considered beyond reasonable doubt, the bioassay performed very well: only 5.6 % of the calf urine samples found compliant in GC/MS/MS were screened false suspect in the bioassay screening method. The bioassay results of non-compliant urine samples under routine conditions were as predicted, taking into account the relative estrogenicity of the natural estrogens 17τ-estradiol and estrone versus 17υ-estradiol. Only one sample was screened false-negative for 17τ-estradiol and estrone. Application of this fast and simple estrogen bioassay in routine surveillance and control can significantly reduce GC/MS/MS sample workload and allow higher percentages of animals to be screened for potential hormone abuse.
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