Resonant mirror-based optical immunosensor:: application for the measurement of atrazine in soil

The affinity biosensor system IAsys based on the resonant mirror optical structure was tested as a direct immunosensor for determination of atrazine in soil. Atrazine as a ligand was immobilized to the aminosilane surface of the measuring cuvette through albumin as a bridge molecule. The interaction of the monoclonal antibody (MAb) D6F3 with the immobilized atrazine was studied, the kinetic affinity equilibrium constant K-A was 1.18 x 10(9) mol(-1) l. The immunosensor was applied to the competitive assay of atrazine in real soil samples. The methanolic extracts of soil were preincubated with MAb (5 min) and the mixture was allowed to interact with the immunosensitive surface of the measuring cuvette (5 min). Thus obtained binding curve was processed with the kinetic program FastFit and the calculated extent of binding served as the parameter for further evaluation. The sensing surface was successfully regenerated using 100 mM NaOH (2 min), the same sensor was used repeatedly for 120 assays. Detection of atrazine concentrations from 0.1 mu g l(-1) to 10 mg l(-1) was evaluated, a practical limit of determination for soil samples was 1 mu g l(-1). The contents of atrazine in 14 real soil samples were determined with the immunosensor and compared to the results of ELISA and gas chromatography. Though correlation between these methods was achieved, the reproducibility of immunosensor data was rather low and further optimization of the measuring procedure is needed. (C) 1999 Elsevier Science B.V. All rights reserved.