Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2005
Publication Date: 12/15/2005
Citation: Kim, H., Shelver, W.L., Xu, T., Li, Q.X. 2005. Automated flow fluorescent immunoassay for the insecticide thiamethoxam. Meeting Abstract. Pacifichem 2005, Honolulu, Hawaii, Dec. 15-20, 2005. Interpretive Summary:
Technical Abstract: A sensitive automated flow fluorescent immunoassay was developed with KinExATM 3000 system for quantitative analysis of the neonicotinoid insecticide thiamethoxam, 3-(2-chlorothiaxol-5-ylmethyl)-5-methyl-4-nitroimino-1,3,5-oxadiazinane. A capillary flow cell contains antigen (thiamethoxam hapten-BSA conjugate)-coated polymethylmethacrylate beads packed at a defined height (3 mm) on a built-in microporous screen. When pre-equilibrated analyte/antibody solution is run through the cell, unbound antibodies are captured on the beads while analyte/antibody complexes are allowed to pass through the screen. Bound antibodies are detected with a secondary antibody labeled with Cy5 fluorescent dye. Cross-reactivity was estimated by measuring the equilibrium constants (Kd) for four other neonicotinoid insecticides (clothianidin, imidacloprid, dinotefuran, and acetamiprid). The concentration of half-maximal inhibition (I50) was obtained by plotting KinExA’s signals to the four parameter sigmoidal curve in the function of analyte concentrations. Monoclonal antibody was very specific to thiamethoxam with < 1% cross activity for tested neonicotinoids. The I50 and the limit of detection were approximately 0.5 micrograms/L and 0.1 micrograms/L, respectively. Thiamethoxam was spiked into stream water samples at concentrations (0, 0.5, 1, 5, and 10 micrograms/L). An excellent correlation (r2=0.99) was obtained between spiked and measured concentrations of thiamethoxam. This assay accurately measured thiamethoxam concentrations in spiked water samples, which suggests that it could be adaptable for high-throughput monitoring of other chemicals of interest.