在分析化学中,分析物稳定性比许多分析师认识到的更常见的混杂因素。在这项研究中,我们评估了31种常见兽药在水中以及牛(牛奶和肾脏/肝脏)和鸡(肌肉和鸡蛋)基质的最终提取物中的稳定性。评估了两种不同的样品制备方法,将最终提取物在典型的房间中储存一个月,冰箱,和冰柜温度。通过三重四极杆和高分辨率技术的液相色谱-质谱(LC-MS)用于分析以不同相关浓度添加的提取物,以用于一般监管目的(10-1000ng/g样品当量)。两个实验室的结果比较表明,在所有测试条件下,稳定的药物(≤20%的损失)包括达诺氟沙星,恩诺沙星,氟苯尼考,氟苯达唑,羟基氟苯达唑,氟美喹,flunixin,5-羟基氟尼辛,林可霉素,还有美洛昔康.被发现是最不稳定的测试药物(在室温下几天内损失>20%)由β-内酰胺(氨苄青霉素,头孢氨苄,氯唑西林,和青霉素G)。奇怪的是,以下抗生素(主要是大环内酯类)在样品提取物中明显比水更稳定:emamectin,红霉素,伊维菌素,lasalocid,莫能菌素,替米考星,泰拉霉素,还有泰乐菌素.那些和其他药物分析物(环丙沙星,多西环素,氟苯尼考胺,2-氨基-氟苯达唑,土霉素,磺胺嘧啶,磺胺二甲氧嘧啶,磺胺二甲嘧啶,和甲氧苄啶)在冷藏提取物中大部分稳定一个月,特别是在较高的浓度下,但并非在所有情况下。在实践中,发现提取物溶液的冰箱储存至少一个月是可以接受的,除了少数例外。
Analyte stability is more commonly a confounding factor in analytical chemistry than many analysts recognize. In this
study, we assessed the stability of 31 common veterinary drugs in water and final extracts of bovine (milk and kidney/liver) and chicken (muscle and egg) matrices. Two different sample preparation methods were evaluated for one-month storage of the final extracts at typical room, refrigerator, and freezer temperatures. Liquid chromatography - mass spectrometry (LC-MS) by triple quadrupole and high-resolution techniques was used for analysis of the extracts spiked at different relevant concentrations for general regulatory purposes (10-1000 ng/g sample equivalent). Comparison of results between two labs demonstrated that stable drugs (≤20% loss) at all tested conditions consisted of danofloxacin, enrofloxacin, florfenicol, flubendazole, hydroxy-flubendazole, flumequine, flunixin, 5-hydroxy-flunixin, lincomycin, and meloxicam. The tested drugs found to be the most unstable (>20% loss at room temperature within a matter of days) consisted of the β-lactams (ampicillin, cefalexin, cloxacillin, and penicillin G). Curiously, the following antibiotics (mostly macrolides) were apparently more stable in sample extracts than water: emamectin, erythromycin, ivermectin, lasalocid, monensin, tilmicosin, tulathromycin, and tylosin. Those and the other drug analytes (ciprofloxacin, doxycycline, florfenicol amine, 2-amino-flubendazole, oxytetracycline, sulfadiazine, sulfadimethoxine, sulfamethazine, and trimethoprim) were mostly stable for a month in refrigerated extracts, especially at higher concentrations, but not in all cases. In practice, freezer storage of extract solutions was found to be acceptable for at least a month, with a few exceptions.