Courtheyn D, Vercammen J, De Brabander H, Vandenreyt I, Batjoens P, Vanoosthuyze K, Van Peteghem C
State Laboratory (ROLG), Ghent, Belgium.
Analyst. 1994 Dec;119(12):2557-64. doi: 10.1039/an9941902557.
For several years, the misuse of dexamethasone and its esters in livestock production has been clearly demonstrated. The first part of the present study deals with the elaboration of a sensitive and specific method for the determination of residues of dexamethasone in excreta at the ppb level. Sample preparation for urine and faeces, including high-performance liquid chromatography (HPLC) fractionation, was carried out. The detection was based on established methodology employing negative chemical ionization-mass spectrometry (NCI-MS) after oxidation of the dexamethasone. In comparison with previous literature, the yield of oxidized dexamethasone was substantially improved and the oxidation procedure was made more simple and robust. In the second part of the study, the relationship between the dose of dexamethasone administered and the levels of the drug in excreta was investigated using this method, as was the ratio between drug levels in urine and faeces. Treatment was carried out for 7 d with an oral dose of 50 mg d-1, the maximum levels found in urine and faeces were 980 and 744 ppb, respectively. While the elimination via faeces responded much slower at the start and the end of treatment, the final part of both excretion profiles were very similar and a level of 1 ppb was reached in both matrices 9 d after the end of treatment. Gas chromatography-mass spectrometry (GC-MS) results obtained for the urine samples were compared with those obtained with direct enzyme immunoassay.
多年来，已明确证实地塞米松及其酯类在畜牧生产中的滥用情况。本研究的第一部分致力于制定一种灵敏且特异的方法，用于测定排泄物中纳克级水平的地塞米松残留量。对尿液和粪便进行了样品制备，包括高效液相色谱（HPLC）分级分离。检测基于既定方法，在氧化地塞米松后采用负化学电离质谱（NCI-MS）。与先前文献相比，氧化地塞米松的产率大幅提高，氧化过程更简便且稳定。在研究的第二部分，使用该方法研究了地塞米松给药剂量与排泄物中药物水平之间的关系，以及尿液和粪便中药物水平的比例。以每日口服剂量50 mg进行7天治疗，尿液和粪便中发现的最高水平分别为980和744 ppb。虽然在治疗开始和结束时，粪便排泄反应较慢，但两种排泄曲线的最终部分非常相似，治疗结束9天后两种基质中的水平均达到1 ppb。将尿液样品的气相色谱-质谱（GC-MS）结果与直接酶免疫测定法的结果进行了比较。
