Development of a disposable electrochemical immunosensor for detection of the herbicide acetochlor

The electrochemical immunosensor for the detection of the herbicide acetochlor was developed. Initially, the feasibility of the immunosensor was verified using the standard ELISA technique employing the competitive assay format with immobilized acetochlor. The assay principle of the disposable immunochemical biosensor was similar. The screen-printed electrode system served as the transducer, acetochlor was covalently immobilized on the surface of the gold working electrode activated with a self-assembled monolayer of cystamine. Acetochlor was linked to this layer through S-acetylmercaptosuccinic anhydride (AMSA). A limited amount of anti-acetochlor polyclonal rabbit antibody in solution competed with the analyzed acetochlor and the secondary goat anti-rabbit antibody labeled with peroxidase was chosen for detection. The amperometric measurement of peroxidase activity was carried out using 5?aminosalicylic acid (ASA) and hydrogen peroxide as substrates. Successful regeneration of the sensing surface was achieved using pepsin at pH 2 when analyzing samples of water. However, deterioration of the sensing surface in the presence of food samples (corn, carrot, potato and milk) required adopting the disposable assay format. The detection limits of the immunosensor were 25 mg/l (drinking water), 60 mg/l (surface water) and 5 mg/l (milk), thus the sensitivity of the immunosensor assay was not sufficient for drinking water analysis. At present, the developed immunosensor allows only qualitative detection of acetochlor above the maximum residual levels in food. The potential repeated use of the immunosensor remains an important issue for future optimization.