Enzyme-Linked Immunosorbent Assay for Simultaneous Detection of Two Fungicides Kresoxim-methyl and Trifloxystrobin in Oranges

Abstract

To assemble an indirect competitive enzyme-linked immunosorbent assay (ELISA) for estimating two strobilurin fungicides at the same time, the hapten was synthesised which contained the common active group, (E)-2-(2-bromo-phenyl)-2-(methoxyimino) acetic acid methyl ester (OEBr) in kresoxim-methyl and trifloxystrobin. The immunogen and coating antigen were respectively prepared through conjugating the above-mentioned hapten with BSA and OVA by the mixed anhydride and activated ester methods, and polyclonal antibodies were produced by immunised rabbits. An enzyme-linked immunosorbent assay was developed for simultaneous detection of kresoxim-methyl and trifloxystrobin. In ELISA, the antiserum showed high affinity and sensitivity to kresoxim-methyl and trifloxystrobin, and their IC₅₀ value and detection limit (expressed as IC₁₀) were 14.7 and 0.0044 µg/ml, respectively, for kresoxim-methyl, and 22.9 and 0.014 µg/ml, respectively for trifloxystrobin. The cross-reaction rate was below 0.1% for other strobilurin fungicides. Recovery study of ELISA from spiked samples of homogenised peeled oranges (final concentrations of 100, 10, and 1 µg/ml) resulted in recovery levels in the range of 82–104%.