Graphite electrodes chemically modified with Prussian Blue (G/PB) were obtained by spreading, on the electrode surface, appropriate volumes of 100 mM K3[Fe(CN)6] and 100 mM FeCl3 solutions, both containing 10 mM HCl. In order to improve the electrochemical response stability, the potential of G/PB electrodes was cycled (in the domain where PB exhibits its electrochemical activity) in 0.1 M KCl solution (G/PB-K), as well as in 2 mM RhCl3 solution,

The toxicity of organophosphorous pesticides is attributed to their ability to inhibit acetylcholinesterase (AChE), which catalyses the hydrolysis of the neurotransmitting agent acetylcholine (ACh). A simple, reproductible and stable AChE-based amperometric bioelectrode was used, for measuring the enzyme activity before and after the incubation with paraoxon dissolved in organic solvents. The inhibition percentage induced by a paraoxon in organic