USDA-ARS, Biosciences Research Laboratory, Fargo, North Dakota 58105, USA.
J Agric Food Chem. 2010 Apr 14;58(7):4077-83. doi: 10.1021/jf904253t.
Three horses were dosed with dietary zilpaterol and the urine concentrations measured from withdrawal day 0 to withdrawal day 21. The analyses were carried out using both enzyme-linked immunosorbent assay (ELISA) and an ultraperformance liquid chromatography with triple-quadrupole-tandem mass spectrometric detection (UPLC-MS/MS). The UPLC-MS/MS method was developed to provide rapid analysis with positive analyte identification by following three product ions and computing the two independent ion ratios. When urinary zilpaterol concentrations were between 0.2 and 2 ng/mL, the ELISA had interday recoveries of 114-120% with coefficients of variation (CV) of <22%; intraday recoveries were 79-111% with CVs of <13%. For urinary zilpaterol concentrations of 0.4-40 ng/mL the UPLC-MS/MS method had interday recoveries of 94-104% with CVs of <8%; intraday recoveries were 97-102% with CVs of < or = 7.5%. Correlation analysis demonstrated that the ELISA and UPLC-MS/MS methods returned essentially the same results, especially at urinary zilpaterol concentrations below 2000 ng/mL. Urinary excretion peaked rapidly after dosing between 5300 and 10800 ng/mL (UPLC-MS/MS) or between 5900 and 17900 ng/mL (ELISA) for the different horses, much higher than observed in other species. Urinary zilpaterol concentrations declined rapidly to below 3000 ng/mL within 24 h of study day 1. After about 5 days, zilpaterol elimination slowed markedly, taking nearly 10 days for an order of magnitude decrease. The analytical methods were able to detect zilpaterol in the urine even at withdrawal day 21, demonstrating the sensitivity of each analytical method and the slow rate of zilpaterol depuration from horses.
三头马给予了饲用莱克多巴胺，从停药日 0 到停药日 21 对尿液浓度进行了测量。采用酶联免疫吸附测定法（ELISA）和超高效液相色谱三重四极杆串联质谱检测（UPLC-MS/MS）对样品进行了分析。UPLC-MS/MS 方法旨在通过对三个产物离子进行跟踪分析，并计算两个独立的离子比率，从而实现快速分析和阳性分析物的鉴定。当尿液中莱克多巴胺浓度在 0.2 到 2ng/mL 之间时，ELISA 的日内回收率为 114-120%，变异系数（CV）<22%；日间回收率为 79-111%，CV<13%。当尿液中莱克多巴胺浓度为 0.4-40ng/mL 时，UPLC-MS/MS 方法的日内回收率为 94-104%，CV<8%；日间回收率为 97-102%，CV<或=7.5%。相关性分析表明，ELISA 和 UPLC-MS/MS 方法得到的结果基本一致，特别是在尿液莱克多巴胺浓度低于 2000ng/mL 时。在不同的马中，给药后尿液排泄迅速达到峰值，在 5300 到 10800ng/mL（UPLC-MS/MS）或 5900 到 17900ng/mL（ELISA）之间，这比在其他物种中观察到的要高得多。在研究日 1 的 24 小时内，尿液中莱克多巴胺浓度迅速下降到 3000ng/mL 以下。大约 5 天后，莱克多巴胺的消除速度明显减缓，大约需要 10 天才能降低一个数量级。分析方法甚至在停药日 21 时仍能检测到莱克多巴胺，这表明了每种分析方法的灵敏度以及莱克多巴胺从马体中缓慢清除的速率。
