Monoclonal antibody-based enzyme-linked immunosorbent assay and lateral flow immunoassay for the rapid screening of paraquat in adulterated herbicides

Abstract

The use of the herbicide paraquat has been banned in many countries due to its high toxicity. However, there is an issue that illegal addition of paraquat in herbicide products. Therefore, a rapid, sensitive, and portable method will be useful to detect paraquat in adulterated herbicides for regulation purpose.In the present study, an indirect competition enzyme-linked immunosorbent assay (icELISA) was developed with a new paraquat-specific monoclonal antibody (mAb) for paraquat detection. The icELISA results showed a 50% inhibitory concentration (IC50) of 7.63 ng/mL with a working range (IC20-IC80) of 1.68–33.1 ng/mL. In addition, a lateral flow immunoassay (LFIA) with a cut-off value of 20.0 ng/mL was also developed. The LFIA showed no detection of the herbicides diquat, glyphosate and glufosinate up to 50 µg/mL. Nine herbicide samples were collected across Hainan province, China and analyzed by the LFIA dipsticks. One out of the nine samples was tested positive, which was confirmed with icELISA and HPLC. The accuracy of the LFIA was further verified through onsite tests in different places in China. Forty-seven commercial herbicide products were tested via the LFIA dipsticks, of which 9 samples were positive and confirmed with HPLC analysis.The paraquat LFIA exhibited the most promising potential as the point of care (POC) device for the rapid screening of paraquat in adulterated herbicide products.