Submitted to: Talanta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2012
Publication Date: 9/4/2012
Publication URL: http://handle.nal.usda.gov/10113/56460
Citation: Xu, T., Xu, Q.G., Li, H., Wang, J., Li, Q.X., Shelver, W.L., Li, J. 2012. Strip-based immunoassay for the simultaneous detection of the neonicotinoid insecticides imidacloprid and thiamethoxam in agricultural products. Talanta. 101:85-90. Interpretive Summary: Nanotechnology was utilized to develop a one-step strip immunoassay. This assay was then applied to the rapid, simultaneous detection of the insecticide residues, imidacloprid and thiamethoxam, in agricultural products such as cucumbers, tomatoes, lettuce, apples, or oranges. The insecticides could be directly determined without troublesome sample pre-treatment procedures and only required diluting sample extracts. The visual results of the assay for all samples were in good agreement with the results measured from a really sophisticated procedure using an expensive instrument called a LC-MS. The new method is clearly easy, rapid and convenient to perform and requires no expensive or complex equipment. With respect to its overall speed and simplicity, this method can be used for screening large numbers of samples and if necessary confirmed with the more expensive LC-MS method.
Technical Abstract: A semiquantitative strip immunoassay was developed for the rapid detection of imidacloprid and thiamethoxam in agricultural products using specific nanocolloidal gold-labeled monoclonal antibodies. The conjugates of imidacloprid-BSA and thiamethoxam-BSA and goat anti-mouse IgG were coated on the nitrocellulose membrane of the strip, serving as test lines and control line, respectively. The flow of the complexes of gold-labeled antibodies and insecticides along the strip resulted in intensive colour formed on the test lines inversely proportional to the concentrations of imidacloprid and thiamethoxam. The visual detection limits of imidacloprid and thiamethoxam in assay buffer were 0.5 and 2 ng mL-1, respectively. Matrix interference of cucumber, tomato, lettuce, apple, and orange on the strip assay could be eliminated by diluting sample extracts with assay buffer. The strip analysis of imidacloprid and thiamethoxam in these samples was compared to liquid chromatography-mass spectrometry and the results were in good agreement. The strip was stable for storage more than 5 months at 4 C. The strip assay is a rapid and simple method for the simultaneous screening of imidacloprid and thiamethoxam in agricultural products.