title: Screening of calf urine for 19-nortestosterone: matrix effect in some immunoassays.
abstract: The performances of three enzyme linked immunosorbent assays (ELISAs) and one radioimmunoassay (RIA) in 17 alpha-19-nortestosterone (17 alpha-19-NT) analysis of bovine urine have been evaluated. Sample preparation was performed by enzymic deconjugation and solid-phase extraction. The main object of the study was the evaluation of the matrix effect, which is generally great in 19-NT immunoassays. Fifty-seven bovine urine samples have been analysed by immunoassay and by gas chromatography-mass spectrometry (GC-MS). The detection limit of GC-MS analysis was 1 microgram l-1. The mean sample blank values in urine analysis were close to 1.5 micrograms l-1 for one ELISA, and 0.4-0.8 microgram l-1 for the other assays (n = 55, samples coming from several breeds in different geographic areas). The detection limits, calculated in compliance to the EEC criteria, were 2.67, 1.97, 2.05 and 5.0 micrograms l-1 for RIA, ELISAs 1, 2 and 3, respectively. The percentage of false positive results adopting this criteria were: 1.8, 3.6, 1.8 and 3.6%. The probability of the occurrence of false negative results was evaluated by adding 2 micrograms l-1 of 19-NT to a negative sample, was high in each assay. Two samples from experimentally treated animals gave positive results both in GC-MS and in immunoassays. The results obtained confirm that by employing immunoassay and solid-phase extraction as sample clean-up, it is not possible to apply the action level (2 ppb) suggested by the European Union (EU).
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, Padova, Italy.
authors.forename: M P
authors.initials: MP
authors.lastname: Oriundi
authors.forename: R
authors.initials: R
authors.lastname: Angeletti
authors.forename: E
authors.initials: E
authors.lastname: Bastiani
authors.forename: C
authors.initials: C
authors.lastname: Nachtmann
authors.forename: K E
authors.initials: KE
authors.lastname: Vanoosthuyze
authors.forename: C
authors.initials: C
authors.lastname: Van Peteghem
mesh_terms: D000818:Animals; D002417:Cattle; D004797:Enzyme-Linked Immunosorbent Assay; D009277:Nandrolone / Q000652:urine*; D011863:Radioimmunoassay
chemical_list: D009277:Nandrolone