The Preparation And Application Of Molecularly Imprinted Polymers For Quinoxalin-2-Carboxylic Acid

Carbadox(CBX) and olaquindox(OLA) are well-known members of quinoxaline-1.4-dioxides, which are widely used as feed additives for promoting growth and preventing swine dysentery and bacterial enteritis in young swine. However, if used non-standard, these drugs will have a certain cumulative toxicity. resulting in poisoning or death of poultry and aquatic animal, or even enter the body through the food chain and cause harm to human health. Quinoxaline-2-carboxylic acid (QCA) and methyl-3-quinoxaline-2-carboxylic acid (MQCA) are the marker residues of CBX and OLA in tissues, and it has been reported that QCA and MQCA were found at trace levels in various samples including chicken, fish, and pork. As the complexity of food matrix, it is necessary to establish a high selective and stable analytical technique with efficient sample pretreatment.In this study, a novel molecularly imprinted polymer (MIP) with good selectivity and sensitivity to QCA and MQCA was prepared using QCA as template, diethylaminoethylmethacrylate(DEEMA) as functional monomer and ethylene glycol dimethacrylate(EDMA) as cross-linker in tetrahydrofuran. The synthesized MIP was characterized by Fourier transform infrared and evaluated through adsorption experiments. The results indicated that MIP exhibited fast kinetics and good selectivity for QCA and MQCA. MIP obtained was used as a selective sorbent of molecularly imprinted solid phase extraction (MISPE) coupled with high performance liquid chromatography for separation and determination of trace QCA and MQCA. Under the optimal conditions, the enrichment factors were74and75for QCA and MQCA respectively, linear plots with r2>0.99were achieved over a range of0.1-10.0μg L-1and relative standard deviation (RSD) for nine parallel determinations were below4.5%.To evaluate the applicability of the developed method, free samples of porcine, chicken and fish were spiked with three levels of QCA and MQCA (2.0μg kg-1.4.0μg kg-1.8.0μg kg-1) and analyzed. The limits of detection (LODs:at S/N=3) of porcine, chicken and fish muscles were0.1,0.3,0.1μg kg-1for QCA and0.2.0.3.0.1μg kg-1for MQCA, respectively. The recoveries ranged from50.0to109.4%and RSDs (n=3) were below5%. A comparison between MIP cartridge and commercially available C18cartridge was made and MIP showed better selectivity for QCA and MQCA than traditional C18material.