ELECTROCHEMICAL SAMPLE PREPARATION FOR THE ENZYMATIC DETERMINATION OFCHOLINESTERASE-INHIBITORS

An electrochemical sample preparation procedure for the enzymatic dete rmination of thione organophosphorus pesticides has been examined. Thi s procedure is based on the galvanostatic electrolysis of thione pesti cides in the presence of chlorides or bromides, in which the pesticide s are oxidized to oxygen analogs. The efficiency of sample preparation depends on the halogen nature. The kinetic studies have shown that, i n the case of bromides, the subsequent determination with a native enz yme (colorimetric detection) is complicated by the mixed character of inhibition. The presence of a reversible component is caused by the pr esence of the residual unoxidized pesticide. With the use of cholinest erase immobilized on paper (a potentiometric biosensor), only the effe ct of an irreversible inhibitor (the major product of electrochemical pesticide oxidation) is observed, regardless of the nature of the oxid ants generated.