Value of alternative sample matrices in residue analysis for stanozolol

Detection of hormones and veterinary drugs in urine samples is limited to the short-term following illegal administration. Alternative sample matrices such as hair or retina are of interest for prolonged detectability of residues. In this preliminary study, we developed sensitive liquid chromatography¿tandem mass spectrometry methods for the confirmatory analysis of stanozolol in different matrices and applied them to urine, retina and hair samples obtained from 11 suspect bovines at the slaughterhouse. Most of the stanozolol metabolite (16-hydroxystanozolol) levels in urine samples were below 0.5 ng ml-1, but nevertheless in some urines traces of this metabolite could still be positively confirmed. Retina samples were all negative so the value of this matrix for stanozolol might be questioned. The hair samples, on the other hand, yielded many positive stanozolol results, and in some animals levels were up to 100-fold higher than the corresponding metabolite levels in urine thereby underlining the potential for prolonged detectability of stanozolol abuse.