Simultaneous determination of Zilpaterol and other beta agonists in calf eye by gas chromatography/tandem mass spectrometry

Adrenergic drugs for growth promotion have been outlawed in European meat production; however, molecules such as Ractopamine and Zilpaterol are licensed for feeding swine and cattle in the United States, Mexico, and South Africa. Analysis of bovine retinal extracts has recently shown considerable extension in the detection period following withdrawal. Previous studies demonstrated that residual concentrations of Clenbuterol and related substances in retinal tissue were > 100 ng/g at day 50 of withdrawal. A method was developed to identify and simultaneously quantify Clenbuterol-like substances with anilinic moieties and drugs with phenolic and catecholic moieties, such as Ractopamine and Zilpaterol, in retinal tissue. The method was validated according to SANCO/1805/2000. After extraction in 0.1 N HCl, samples were cleaned up on C18 non-endcapped solid-phase extraction columns and analyzed as trimethylchlorosilane derivatives by gas chromatography/tandem mass spectrometry, electron impact mode. At concentrations of agonists between 62.5 and 250.0 ng/g in bovine retina, mean recoveries ranged from 85.3 to 94.8%, repeatability was < 9.6%, and within-laboratory reproducibility was < 10.5%. The decision limits (CCalpha) were within the range of 66.3-70.4 ng/g, and the detection capability (CCbeta) varied from 73.9 to 79.8 ng/g. Results are discussed in terms of a multiresidue approach to improve reliability of the monitoring strategy.