Submitted to: Food and Agricultural Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2011
Publication Date: 8/30/2011
Citation: Shelver, W.L., Smith, D.J. 2011. Immunochemical-based zilpaterol measurement and validation in urine and tissues. Food and Agricultural Immunology. 22(3):247-258.
Interpretive Summary: Zilpaterol is a growth promoter approved for use in cattle in Mexico, South Africa, and the United States but not in any other countries. It is important to have analytical methods capable of demonstrating the animal products are below the allowed tissue residue level or free from Zilpaterol to ensure food is safe for consumption. Unless allowed residues are met, the country may not allow imports to enter the country, thereby producing a huge negative effect on trade. In this book chapter, different analytical methods that were used to determine zilpaterol in urine or tissues have been reviewed. A critical comparison of the different methods is made with the strengths and weaknesses of the methods described. It is important to compare the methods to expose any biases that might be present causing one laboratory to obtain different results. In addition, zilpaterol elimination patterns among the animals are compared. This comparison is important as it provides a scientific basis for withdrawal time needed to reduce zilpaterol levels to the required levels.
Technical Abstract: Because of abuse potential of the ß-agonist feed-additive zilpaterol, a need exists for rapid, sensitive and specific qualitative and quantitative zilpaterol analyses. Ideally, such analytical assays would be adaptable to high throughput format across multiple applications. In addition, the assay would be amenable for use by academic, industrial, and (or) regulatory interests. To this end, a polyclonal antibody based enzyme linked immunosorbent assay (ELISA) was developed and tested. Due to limitations in the polyclonal antibody assay, monoclonal antibodies were generated and the most promising antibodies were thoroughly explored for their usefulness for agricultural applications. In addition, a zilpaterol assay utilizing an immunobiosensor format was developed and optimized considering both monoclonal and polyclonal antibodies. Assays were developed and their utility tested by measuring tissue and urinary concentrations of zilpaterol from sheep that had been treated with dietary zilpaterol for 10 days. Residue data were determined by zilpaterol ELISA and a quadrupole time-of-flight liquid chromatography-tandem mass spectrometric (qTOF-LC-MS/MS) method. The study demonstrated that sheep eliminated zilpaterol rapidly via the urine with tissue residues also falling rapidly after zilpaterol withdrawal. A zilpaterol study in horses used ELISA and ultra-high pressure LC-triple quadrupole-MS/MS (UHPLC-TQ-MS/MS) to measure zilpaterol depuration in urine. The study 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 both the ELISA and UHPLC-TQ-MS/MS method 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 a biosensor method provided greater precision than the ELISA procedure.