Determination of fenhexamid residues in grape must, kiwifruit, and strawberry samples by enzyme-linked immunosorbent assay

Fenhexamid is a new-generation agrochemical extensively used nowadays to protect high valuable crops and fruits from fungus attacks. In this paper, the development of an indirect competitive immunoassay for the determination of fenhexamid residues in fruit samples is described. After optimisation of immunoreagent concentrations, the assay, based on monoclonal antibody FHo4#27, showed high sensitivity, and selectivity, with a limit of detection for fenhexamid standards in buffer of 0.04 μg/L. The influence of several physico-chemical factors, including pH, ionic strength, solvent tolerance, and matrix interferences on the analytical parameters of the standard curve was studied. For spiked liquid food samples like grape must, just a direct 1:50 dilution in water was sufficient to attain recoveries between 100% and 110%. For kiwifruit and strawberry samples, a double extraction procedure with methanol is proposed in this study, which afforded recovery values that ranged between 103% and 116%. The limit of quantification of the developed assay was 5 μg/kg for grape must, 10 μg/kg for kiwifruits, and 25 μg/kg for strawberries. The optimised assay was compared with a reference procedure based on liquid chromatography using incurred samples from the market, and an excellent correlation between both methods was found.