Immunosensor for 2,4-dichlorophenoxyacetic acid in aqueous organic solvent soil extracts

The development of a simple electrochemical immunoassay procedure for the field-based quantification of the herbicide 2,4-D in methanolic soil extracts is presented. The sensor utilizes a competitive immunoassay format incorporating an immobilized antigen complex at the surface of a disposable screen-printed working electrode element, The extent of glucose oxidase-labeled antibody binding td the antigen-electrode is determined amperometrically and is related to sample analyte concentration. The performance of the sensor is assessed in buffer, 30% methanol, and methanolic soil extracts. The device is capable of quantifying 2,4-D in all three matrixes at the low ppm level with coefficient of variation values of 6.2-33.6%. The causes of the variation observed in the sensor response indifferent soil matrixes are examined and improvements proposed. The sensor, tested in parallel with a commercial 2,4-D immunoassay test kit, yields comparable quantitative data and detection limits while exhibiting greater assay simplicity.