A micro flow injection electrochemical biosensor for organophosphorus pesticides

We describe a disposable, amperometric micro flow injection electrochemical biosensor that can be applied to the identification and quantification of highly toxic organophosphorus (OP) compounds in the environment, on the spo t and in a short time. The system traces very small quantities of OP by mon itoring the enzymatic reaction of acetylcholine esterase (AChE) and its inh ibition. The sensor is sensitive, rapid, small, inexpensive, disposable and can be operated by non-professional technicians. The electrochemical cell consists of screen-printed electrodes covered with an enzymatic membrane an d placed in a home-made flow cell. The electrodes are connected to a comput er-controlled potentiostat. We quantitatively detected the OP compound, dim ethyl 2,2-dichlorovinyl phosphate (DDVP), by monitoring the OP induced decr ease in enzymatic degradation of the substrate, acetylthiocholine chloride (ATCh), to thiocholine and acetic acid. Thiocholine reacts with hexacyanofe rrate ion in the working solution and the reduction of [Fe(CN)(6)](-3) to [ Fe(CN)(6)](-4) and its subsequent reoxidization by the electrode generates very sharp, rapid and reproducible electric signals. The ability to detect low quantities is extremely important when dealing with hazardous environme ntal pollutants. (C) 2000 Elsevier Science S.A. All rights reserved.