Abstract: This paper reports the development of a novel detection method, based on the coupling of a biosensor measuring device and a flow injection system, using the enzyme formaldehyde dehydrogenase and a Os(bpy)(2)-poly(vinylpyridine) (POs-EA) chemically modified screen-printed electrode. The sensor can detect 30 ng mL-1 of formaldehyde in aqueous solution (corresponding to sub-ppb atmospheric concentrations of formaldehyde). The sensor is selective, inexpensive, stable over several days, and disposable, as well as simple to manufacture and operate. The system described here can easily be adapted to other substrates using their corresponding dehydrogenases.

Abstract: 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 spot and in a short time. The system traces very small quantities of OP by monitoring the enzymatic reaction of acetylcholine esterase (AChE) and its inhibition. 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 and placed in a home-made flow cell. The electrodes are connected to a computer-controlled potentiostat. We quantitatively detected the OP compound, dimethyl 2,2-dichlorovinyl phosphate (DDVP), by monitoring the OP induced decrease in enzymatic degradation of the substrate, acetylthiocholine chloride (ATCh), to thiocholine and acetic acid. Thiocholine reacts with hexacyanoferrate 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 environmental pollutants.