Imprinted polymer based sensor system for herbicides using differential-pulse voltammetry on screen printed electrodes

A sensor system for the herbicide 2,4-dichlorophenoxyacetic acid has been d eveloped based on specific recognition of the analyte by a molecularly impr inted polymer and electrochemical detection using disposable screen-printed electrodes. The method involves a competitive binding step with a nonrelat ed electrochemically active probe. For batch binding assays, imprinted poly mer particles are incubated in suspension with the analyte and the probe, f ollowed by centrifugation and quantification of the unbound probe in die su pernatant. Two different compounds, namely 2,4-dichlorophenol and homogenti sic acid, were tested as potential electroactive probes. Both compounds cou ld be conveniently detected by differential-pulse voltammetry on screen-pri nted, solvent-resistant three-electrode systems having carbon working elect rodes. Whereas 2,4-dichlorophenol showed very high nonspecific binding to t he polymer, homogentisic acid bound specifically to the imprinted sites and thus allowed calibration curves for the analyte in the micromolar range to be recorded. An integrated sensor was developed by coating the imprinted p olymer particles directly onto the working electrode. Following incubation of the modified electrode in a solution containing the analyte and the prob e, the bound fraction of the probe is quantified. This system provides a ch eap, disposable sensor for rapid determination of environmentally relevant and other analytes.