Research and application of rapid detection techniques for 10 pesticide residues in cowpea

An immunoassay method for rapid detection of 10 pesticides, including carbofuran, triazophos, chlorpyrifos, acetamiprid, iprodione, pyraclostrobin, carbendazim, procymidone, cyromazine and fenpropathrin, was established in cowpea, and it was applied to the on-site rapid screening of pesticide residues in cowpea samples. According to the principle of immune-chromatography, the gold immune-strips were prepared using pesticide antigens and antibodies. The concentration of antigens, pH value and labeling amount of gold labeled antibodies for the test-strips of the 10 pesticides, and the sample preparation method for cowpea samples were optimized. The sensitivity, accuracy, and cross reaction of the fast detection method were investigated. The detection limits of the established rapid immunoassay method for pesticides in cowpea were 0.02 mg/kg for carbofuran, 0.05 mg/kg for triazophos, 0.25 mg/kg for chlorpyrifos, 0.025 mg/kg for acetamiprid, 0.5 mg/kg for iprodione, 1.0 mg/kg for pyraclostrobin, 0.5 mg/kg for carbendazim, 0.1 mg/kg for procymidone, 0.25 mg/kg for cyromazine, and 0.5 mg/kg for fenpropathrin. Its sensitivity meets the requirements of the National Food Safety Standard - Maximum Residue Limits for Pesticides in Food (GB 2763—2021) in China. The sample preparation takes 5 min and the immune-strip detection takes 10 min, which means it only takes 15 min to complete the pesticide residue detection in cowpea samples. The method also has the advantages of low cost and easy operation. The rapid detection results of 10 independently spiked samples of cowpea showed a false positive rate of 0, a false negative rate of ≤ 11.1%, and an accuracy rate of ≥ 94.4%. The method was applied to the detection of cowpea samples collected from multiple locations in Zhejiang Province, and it showed that the results of the immunoassay rapid detection method were consistent with those of the reference instrumental method, with an accuracy rate of over 97.2%. In the safety monitoring of agricultural products, this method provides technical support for the on-site rapid detection of pesticide residues. The method has good practicability and high sensitivity, and it is time-saving and labor-saving, and is suitable for the on-site rapid detection of 10 commonly used pesticides in cowpea.