Development Of A Method For The Rapid Determination Of Pyrethroids

Pyrethroids are widely used in the pest control of fruits and vegetables due to their low toxicity,high efficiency and low residue.At present,the detection method of pyrethroids is mainly chromatographic analysis,the large instruments used in these methods are not only expensive but also complicated to operate.Therefore,it is urgent to explore a simple,effective,rapid and sensitive method for the detection of pyrethroid.In this study,an indirect competitive enzyme-linked immunosorbent assay(ELISA)was established to detect the pyrethroids.Furthermore,the preliminary study was made to explore the possibility of combining ELISA with QuEChERS pretreatment for the detection of pyrethroids in fruits and vegetables.The main results were as follows:(1)Coating antigens were prepared by coupling hapten PBA to carrier protein OVA by EDC method and mixed anhydride method,respectively,with the molar reaction ratio of 30:1,45:1 and 60:1.The conjugations were identified by UV spectrum scanning and SDS-PAGE.Working concentrations of antigens,affinity constants between antigens and antibodies,cross reaction and sensitivities of ELISA were evaluated to screen the optimal coating antigen.Finally,coating antigen named MA2 was selected for further study.(2)Organic solvent,ionic strength and p H value of indirect competitive ELISA were optimized,which were as follows:ionic strength was 10 mmol/L,p H value was 7.4,and 10%(v/v)methanol was used for the dissolution of pyrethroids in the aqueous phase.The standard inhibition curves of pyrethroids were established and the multi-residue detection was evaluated by cross reaction.The results showed that the established ELISA method could effectively identify eight pyrethroids with the IC₅₀ range of8.69 ng/m L to 344.97 ng/m L.The IC₅₀ value of fenpropathrin,cyphenothrin and cyfluthrin were 8.69 ng/m L,79.53 ng/m L and 84.08 ng/m L,and the detection limits of these three were 1.32 ng/m L,38.85 ng/m L and 43.22ng/m L,respectively.(3)The recovery experiments on vegetables,fruits and tea were conducted via pre-treated according to QuEChERS method in Chinese national standards,GB 23200.113-2018,and detected by the established ELISA method.The results showed that the extraction of vegetable and fruit samples had strong matrix effects,so that the detection value was invalid.On the other hand,green and black tea had a weaker matrix effect,but a lower recovery rate.The ELISA method established in this study was used to detect tea samples treated by the modified QuEChERS method.The results showed that the matrix effects of black tea and green tea were significantly reduced.This indicated that the established ELISA method had the potential to detect pyrethroids in a variety of food samples with appropriate pretreatment.