Automated flow fluorescent immunoassay for part per trillion detection of the neonicotinoid insecticide thiamethoxam.

An ultra sensitive automated flow fluorescent immunoassay was developed using the KinExAtrade mark 3000 system for quantitative analysis of the neonicotinoid insecticide thiamethoxam. Five new monoclonal antibodies were obtained and screened with a competitive ELISA. One monoclonal antibody designated as E6VI was evaluated for sensitivity, selectivity and solvent tolerance with the KinExA. Sensitivity determined from the concentration of half-maximal inhibition (IC50) was obtained by plotting KinExA signals to a four-parameter sigmoidal curve as a function of analyte concentrations. For the most sensitive clone, the IC50 and the limit of detection were approximately 30 pg ml(-1) and 16 pg ml(-1), respectively. Cross-reactivity was estimated by measuring the equilibrium constants (K(d)) for four other neonicotinoid insecticides (clothianidin, imidacloprid, dinotefuran, and acetamiprid). E6VI was very specific to thiamethoxam with <0.11% cross-reactivity for tested neonicotinoids. An excellent correlation (r2=0.99) was obtained between spiked and measured concentrations of thiamethoxam in stream and tap water, potato, cucumber, and apple samples.