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.