National Reference Laboratory for Veterinary Drug Residue Beijing Center, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Anal Bioanal Chem. 2013 Mar;405(8):2653-9. doi: 10.1007/s00216-012-6696-x. Epub 2013 Jan 27.
Methyl-3-quinoxaline-2-carboxylic acid (MQCA) is a possible residue marker for three quinoxaline veterinary medicines (olaquindox, mequindox, and quinocetone). The wide application of mequindox/quinocetone or the illegal use of olaquindox leads to MQCA residue in animal's original food, thereby threatening the safety of human food. The indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) with a specific coating antigen and monoclonal antibody (MAB) was established and optimized for detecting MQCA in swine liver. Samples were acidified with 2 mol l(-1) hydrochloric acid, extracted with ethyl acetate-hexane-isopropanol (8 + 1 + 1, v/v/v) and then detected by IC-ELISA. The logarithm correlation of standards to OD values ranged from 0.2 to 200 μg l(-1), with IC(50) of 6.46 μg l(-1). Negligible cross-reactivity happened to five quinoxaline antibiotics (olaquindox, mequindox, quinocetone, carbadox, and cyadox) and the metabolite of carbadox and cyadox (quinoxaline-2-carboxylic acid). When spiked with 1 to 100 μg kg(-1) of MQCA, the recoveries ranged from 85.44 to 100.02 %, with the intra-assay coefficient of variation (CV) of 6.64-10.57 % and inter-assay CV of 7.29-10.88 %. The limit of detection for MQCA was 1.0 μg kg(-1) in swine liver. Furthermore, incurred samples were detected by the IC-ELISA and then conformed by a reported LC/MS/MS method, it shown that there was good correlation between the two methods. All these results indicated that the IC-ELISA method is appropriate for surveillance MQCA residue in animal tissues.
3-甲基喹喔啉-2-羧酸（MQCA）是三种喹喔啉类兽药（喹乙醇、喹烯酮和喹肟酮）的可能残留标志物。由于喹烯酮/喹肟酮的广泛应用或喹乙醇的非法使用，MQCA 残留在动物的原始食物中，从而威胁到人类食物的安全。建立并优化了一种基于特异性包被抗原和单克隆抗体（MAB）的间接竞争酶联免疫吸附试验（IC-ELISA），用于检测猪肝脏中的 MQCA。样品用 2 mol/L 盐酸酸化，用乙酸乙酯-正己烷-异丙醇（8+1+1，v/v/v）提取，然后用 IC-ELISA 检测。标准品的对数与 OD 值的相关性范围为 0.2 至 200 μg/L，IC50 为 6.46 μg/L。五种喹喔啉类抗生素（喹乙醇、喹烯酮、喹肟酮、卡巴氧和喹恶啉羧酸）及其代谢物（喹喔啉-2-羧酸）与该方法几乎没有交叉反应。当以 1 至 100 μg/kg 的 MQCA 进行添加时，回收率范围为 85.44 至 100.02%，批内变异系数（CV）为 6.64-10.57%，批间 CV 为 7.29-10.88%。猪肝脏中 MQCA 的检测限为 1.0 μg/kg。此外，用 IC-ELISA 检测到的实际样品，然后用报道的 LC/MS/MS 方法进行确认，两种方法之间存在良好的相关性。所有这些结果表明，IC-ELISA 方法适用于监测动物组织中的 MQCA 残留。
