Fluorescence polarisation immunoassays for strobilurin fungicides kresoxim-methyl, trifloxystrobin and picoxystrobin

Fluorescence polarisation immunoassays (FPIAs) based on monoclonal antibodies for detection of three strobilurin fungicides - kresoxim-methyl (KM), trifloxystrobin (TF) and picoxystrobin (PC), were developed and optimised. Fluorescein-labelled derivatives of target antigens (tracers) were synthesised and purified by thin layer chromatography. Influence of tracer structures on the assay parameters was investigated. For KM and TF, the best assay performance was achieved with the homologous pairs of reagents. For the PC assay, the heterologous tracer, i.e. fluorescein-labelled derivative of TF, was used. The developed FPIAs were applied to the determination of KM, TF and PC in red wine. Most optimal sample preparation was achieved with cross-linked poly(vinylpyrrolidone) as a sorbent. This clean-up is simple, rapid and allows determination of all three strobilurin fungicides in one sample. Detection limits of the developed FPIAs in red wine were 28, 6 and 5 ng/mL for KM, TF and PC, respectively. Recovery in spiked samples averaged between 80% and 104%. Intra- and inter-assay coefficients of variance were less than 12%. The developed FPIA methods can be applied to screening of wine samples for KM, TF and PC residues without complicated cleanup.