Amperometric proton selective strip-sensors with a microelliptic liquid/gel interface for organophosphate neurotoxins

A novel strip-based disposable amperometric proton sensor that can selectively detect organophosphate neurotoxins (i.e., paraoxon) is described. The detection methodology is based on measuring the current change involved in the assisted proton transfer by a proton selective ligand (e.g., ETH 1778) across a microelliptic hole interface between the aqueous and polyvinylchloride-2-nitrophenyloctylether gel phase. The selective detection of paraoxon is achieved by measuring protons released by the specific hydrolysis of paraoxon with the organophosphorus hydrolase enzyme. A two-step process involving the hydrolysis and proton transfer reaction was characterized using cyclic voltammetry and differential pulse stripping voltammetry. A strip-based sensor fabricated using a simple polydimethylsiloxane (PDMS) mold with the resulting device was found to exhibit a linear response over a wide range of paraoxon concentrations (0.5 μM-100 μM) present in aqueous samples. In addition to the excellent detection limit and a wide dynamic range, a superb selectivity in the presence of common interfering agents in agricultural samples is achieved.