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

The affinity biosensor system IAsys based on the resonant mirror optical st ructure was tested as a direct immunosensor for determination of atrazine i n 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 st udied, 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 M Ab (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 bin ding served as the parameter for further evaluation. The sensing surface wa s successfully regenerated using 100 mM NaOH (2 min), the same sensor was u sed 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 determinati on for soil samples was 1 mu g l(-1). The contents of atrazine in 14 real s oil samples were determined with the immunosensor and compared to the resul ts of ELISA and gas chromatography. Though correlation between these method s was achieved, the reproducibility of immunosensor data was rather low and further optimization of the measuring procedure is needed. (C) 1999 Elsevi er Science B.V. All rights reserved.