Design and development of heterologous competitive immunoassays for the determination of boscalid residues†
Boscalid is a modern agrochemical belonging to the so-called chemical class of succinate dehydrogenase inhibitor fungicides. With the aim of developing rapid analytical screening methods for this relevant compound, we herein report the synthesis of new boscalid mimics and the study of their suitability for the production of polyclonal antibodies. Aliphatic spacer arms equivalent in length and composition were tethered at two different aromatic rings of the target molecular structure. These haptens, besides being used for immunization, were employed in the development of heterologous competitive enzyme-linked immunosorbent assays (cELISAs) in order to improve assay detectability. Direct and indirect immunoassays were tailored and applied to the determination of samples with incurred boscalid residues. The assays were characterized in terms of sensitivity, specificity, trueness, and precision. Limit of quantification was established at 5 μg kg−1, coefficients of variation were lower than 20%, and recoveries from spiked samples ranged from 90 to 137%. Finally, ELISA performance was evaluated by Deming regression analysis with tomato and cucumber samples, selecting ultra-performance liquid chromatography-mass spectrometry as the reference method. The results showed that the proposed cELISAs are useful for the routine determination of boscalid fungicides in foods with high-sample throughput and affordable cost.