Development of a bi-enzyme tracer competitive enzyme-linked immunosorbent assay for detection of thiacloprid and imidaclothiz in agricultural samples.

A bi-enzyme tracer direct competitive enzyme-linked immunosorbent assay (dc-ELISA) was developed based on anti-imidaclothiz and anti-thiacloprid antibodies. Several affected physicochemical factors were optimised, including methanol concentration, ionic strength and pH value. Under the optimised conditions, 50% inhibiting concentration (IC50) values for thiacloprid and imidaclothiz were 182.62 and 58.17 μg/L, with a limit of detection (LOD) of 4.25 and 2.12 μg/L, respectively. There was no obvious cross reactivity (CR) between the two pesticides with most neonicotinoids pesticides except imidacloprid. The method analyzing the spiked samples of tomato, pear and cabbage showed satisfying recoveries (85.27-113.07%). Comparable dissipation of thiacloprid and imidaclothiz in authentic tomato samples determined with the dc-ELISA and high performance liquid chromatography (HPLC) indicated that dc-ELISA is suitable for monitoring thiacloprid and imidaclothiz residues simultaneously in agricultural samples.