Abstract
Establishment of an analytical method on zilpaterol (ZPT), the beta-agonists, and a growth promoting agent for livestock was undertaken. Analytical method for ZPT in the beef by LC-ESI-MS/MS was adopted. Before sample extraction, a beef sample was hydrolyzed by beta-glucuronidase/arylsulfatase and 0.2 M ammonium acetate buffer solution. Afterwards, the mixture was extracted with ethylacetate and then defatted by n-hexane/methanol partitioning. Subsequently, the separated organic layer was evaporated and the dissolved solution was purified by using a Molecular Imprinted Polymer solid phase extraction. The quantitation was carried out using LC-ESI-MS/MS with C18, a non-polarity column under the gradient condition with 10 mM ammonium acetate (pH 4.3) : acetonitrile (95 : 5 (v/v), a mobile phase A) and acetonitrile (a mobile phase B). The standard calibration curve presented linearity of correlation coefficient (r2) > 0.999, analyzed from 0.2 to 10 ng/mL. The limit of quantitation in a beef showed 0.2 µg/kg. The average recoveries of intra- and inter-day experiment ranged from 100.9 to 108.5% and 103.3 to 104.5%, respectively. The repeatability and reproducibility for intra- and inter-day measurement expressed as a relative standard deviation was less than 10.0%, respectively. Therefore, the established analytical method for ZPT residue in beef was applicable to the official analytical method with the acceptable level of sensitivity, repeatability and reproducibility.
