Screen-printed amperometric immunosensor for repeated use in the flow-through mode

The screen-printed electrochemical system was used for construction of the regenerable flow-through immunosensor for determination of the herbicide 2, 4-dichlorophenoxyacetic acid (2,4-D). The gold-based composite electrode wa s modified with a self-assembled monolayer of cysteamine and the obtained a minogroup was linked to 2,4-D using the common N-hydroxysuccinimide/carbodi imide reaction. This immunosensor was employed in a flow-through system wit h the monoclonal antibody E2/G2 conjugated to peroxidase as a tracer. The p eroxidase activity retained in immunocomplexes at the electrode surface was quantified amperometrically at -50 mV vs. the screen-printed silver pseudo reference electrode, hydrogen peroxide and iodide were used as substrates. Repeated use of the immunosensor was successfully achieved using regenerati on with pepsin at pH 2 at the end of each assay cycle. The calibration plot for the competitive determination of 2,4-D was constructed from 0.01 to 10 0 mu g/L; limit of detection (based on the 20 % decrease of relative bindin g of the tracer) was 0.12 mu g/L. One analytical cycle lasted for 30 min; t he same immunosensor can be used for 20 assays. Performance of similar elec trochemical immunosensors based on the same antibody clone is compared.