Acid hydrolysis of military standard formulations of diazinon

Acid hydrolysis is a means of disposal of diazinon, O,O-diethyl-O-(2-isopropyl-4-methyl-6-pyrimidinyl)-phosphorothioate. Procedures were developed for the hydrolysis of three military standard diazinon formulations (47.5% emulsifiable concentrate, 2% dust and 0.5% oil solution). The kinetics of hydrolysis at four temperatures were obtained for each formulation in order to predict the half-life of diazinon between 5 degrees and 50 degrees C. The toxicities of the reaction mixtures were evaluated by aquatic bioassay with bluegill sunfish (Lepomis macrochirus). When the hydrolysis of a formulation had reduced the diazinon concentration by greater than 99.9%, there was less than 50% reduction in the toxicity of the reaction mixture to bluegill sunfish. Analysis of reaction mixtures showed that the toxic component was O,O,O,O-tetraethyldithiopyrophosphate (Sulfotepp), which was present in all diazinon formulations.