Immobilized parathion hydrolase: an amperometric sensor for parathion.

An amperometric enzyme biosensor for the direct measurement of parathion was developed. The biosensor is based on parathion hydrolase from Pseudomonas sp. isolated from contaminated soil. The enzyme, which was immobilized on a carbon electrode, catalyzes the hydrolysis of parathion to form p-nitrophenol, which was detected by its anodic oxidation. The enzymatic and electrochemical reactions were examined and optimized. Screen-printed electrodes and a microflow injection system provide the means to significantly reduce the volume of the detected samples. Pulsed techniques further increased the sensitivity of the measurement. The current signal was linearly related to the parathion concentration, and the detection limit was less than 1 ng/mL. The biosensor is rapid as well and can be used outdoors and indoors by a nonqualified person.