A fast immunoassay for the screening of beta-agonists in hair.

Hair has been shown to be an excellent site for the accumulation of clenbuterol residues. Compared with other matrices, hair sampling is very easy and this might result in large numbers of samples. In this study, a simple digestion-extraction procedure was combined with a sensitive clenbuterol ELISA, which resulted in an easy screening procedure suitable for the detection of at least four beta-agonists. Hair from untreated cows (n = 40) resulted in low blank levels (0.9 +/- 0.7 and 0.5 +/- 0.2 ng g-1 for black and white hair, respectively). The detection limits for clenbuterol, bromobuterol, mapenterol and mabuterol were determined as 1-1.5 ng g-1 for white and 3-4 ng g-1 for black hair. The accumulation of mabuterol and mapenterol in black and white hair from treated calves was demonstrated by GC-MS. The screening assay is not suitable for the detection of cimbuterol (owing to the low extraction efficiency) and for salbutamol and terbutaline (owing to the low cross-reactivity of the antibodies used for the ELISA and the low extraction efficiency). Black hair samples from cows treated with clenbuterol were still found to be positive (> 5 ng g-1) at 23 weeks after treatment. The fast screening procedure is a powerful means to detect and track the illegal use of clenbuterol, bromobuterol, mabuterol and mapenterol in animal production.