Immunoassays for trifloxystrobin analysis. Part II. Assay development and application to residue determination in food

• Two new monoclonal antibody-based immunoassays to trifloxystrobin were characterised.
• An indirect assay for trifloxystrobin and its metabolite was developed.
• Competitive ELISAs were validated with blind-spiked and in-field treated samples.

Immunochemical assays constitute complementary analytical methods for small organic molecule determination. We herein describe the characterisation and optimisation of two competitive enzyme-linked immunosorbent assays in different formats using monoclonal antibodies to the Quinone outside inhibitor (QoI) fungicide trifloxystrobin. Antibody selectivity was evaluated using a variety of agrochemicals and the main trifloxystrobin metabolite. Acceptable tolerance of the immunoassay to methanol, ethanol, and acetonitrile was observed in all cases, whereas a dissimilar influence of buffer pH and ionic strength was found. Moreover, the influence of Tween 20 over the analytical parameters was studied. The limits of detection of the optimised assays were below 0.1 μg L−1. Excellent recoveries, even at 10 μg kg−1, were obtained when strawberry, tomato, and cucumber samples spiked with trifloxystrobin were analysed. Finally, statistical agreement was found between immunoassay and reference chromatographic results using blind-spiked and in-field treated samples.