Use of biosensors for rapid drug residue analysis without sample deconjugation or clean-up: a possible way forward

The drug salbutamol (SBL) is a beta-agonist that may be used illegally as a n animal growth promoter. SBL is also a good example of a drug which is exc reted in the form of glucuronides and sulfates. Such metabolites cause comp lexities in analysing for the presence of drug residues. In the majority of cases a process of deconjugation and sample clean-up is required prior to analysis. This is both time consuming and causes some loss of accuracy. In this study, the urine of calves treated with SBL orally for 3 d was collect ed during and after medication. Samples were assayed before and after hydro lysis by two different methods, radioimmunoassay (RIA) and a newly develope d biosensor immunoassay (BIA). Some samples were also analysed by CC-MS. Th e results clearly showed that both screening assays (RIA and BIA) found hig h concentrations of SBL residues throughout the study, This was especially true in the BIA method. It was also demonstrated that urine sample analysis without the need for deconjugation or clean-up could be achieved. Results obtained by CC-MS tended to be an order of magnitude lower than the corresp onding screening test results. This work showed that biosensor based veteri nary drug residue testing procedures can be developed which can generate re sults in real time without the need for time consuming sample preparation.