A convenient method for oxidation of organophosphorus pesticides in organic solvents

Since organophosphorus pesticides can be oxidized to oxons in vivo and in t he environment and their determination based on inhibition of cholinesteras es can be more sensitive after their oxidation to oxons, development of an efficient method for their in vitro oxidation is important for their toxico logical and analytical studies. This study demonstrated that treatment of o rganophosphorus pesticides with 10 molar excess bromine in acetonitrile is a rapid and efficient method for their oxidation. For the nine organophosph orus pesticides tested, the reaction was complete within a few seconds. All reactions gave the respective oxons as single major product, except that o f fenthion, which gave two major products, the respective oxon and another product from further oxidation of the oxon, The yields of the oxons were 82 -100%. The inhibitory power of the pesticides on acetylcholinesterase befor e and after oxidation was measured and, for all pesticides tested, the powe r after oxidation was much higher than that before oxidation. Inhibition ca libration curves for both unoxidized and oxidized forms of fenitrothion and parathion were obtained. The sensitivity of the detection of these pestici des was much higher after oxidation. (C) 2000 Academic Press.