A sensitive and specific ELISA for determining a residue marker of three quinoxaline antibiotics in swine liver.
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.
National Reference Laboratory for Veterinary Drug Residue Beijing Center, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Linli
L
Cheng
Jianzhong
J
Shen
Zhanhui
Z
Wang
Wenxiao
W
Jiang
Suxia
S
Zhang
D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis* / Q000378:metabolism; D003257:Consumer Product Safety; D004350:Drug Residues / Q000032:analysis* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005506:Food Contamination / Q000032:analysis / Q000517:prevention & control; D006801:Humans; D008099:Liver / Q000737:chemistry* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D011810:Quinoxalines / Q000032:analysis* / Q000378:metabolism; D013552:Swine
D000900:Anti-Bacterial Agents; D011810:Quinoxalines