Immunochemical-based zilpaterol measurement and validation in urine and tissues

Because of abuse potential of the feed-additive zilpaterol, a need exists for rapid, sensitive and specific analyses. Polyclonal and monoclonal antibody-based enzyme-linked immunosorbent assays (ELISAs) were developed and their usefulness for agricultural applications explored. Immunobiosensor formats were developed for both monoclonal and polyclonal zilpaterol antibodies. Zilpaterol ELISA and immunobiosensor were tested by measuring tissue and urinary concentrations from sheep treated with zilpaterol for 10 days. The study demonstrated that sheep eliminated zilpaterol rapidly. A zilpaterol study in horses demonstrated that urinary zilpaterol in horses was initially much higher than in other species and that urinary zilpaterol depleted in a biphasic manner. Zilpaterol was detectable using either ELISA or ultra-high performance liquid chromatography-triple quadrupole-tandem mass spectrometry (UHPLC-TQ-MS/MS) after 21 days of withdrawal in horses. These studies demonstrated that the ELISA procedure was rapid and was in good agreement with instrumental methods while the biosensor method provided greater precision than the ELISA procedure.