Study On Environmental Behavior Of Insecticide Pyraclofos

While the majority of pesticides are achiral,about 25%of pesticides currently used are chiral and therefore consist of mixture of enantiomers. Enantiomers of chiral compounds usually differ in biological activities because of their different interactions with enzymes and other naturally occurring chiral molecules.However,most of the chiral pesticides are still marketed and applied in racemates.The enantiomeric separation and environmental behaviors of chiral pesticides have so far received limited research.In the present work,the enantiomeric separation,biotoxicity and transfer in environment of Pyraclofos was investigated.The detailed information is as follows:(1)The hydrolysis of pesticide pyraclofos were investigated.The kinetics of hydrolysis of pyraclofos were investigated at different pH values and under various temperatures.The results are found:①:Pesticide pyraclofos is stable in acidic and neutral water,but readily hydrolyzed in alkaline water.Furthermore,the higher the pH value,the faster the hydrolysis rate.②:The rate of hydrolysis is increased as the hydrolysis temperatur increase. (2)The adsorptions of pesticides pyraclofos in different soils were studied.The isotherm data were fitted to the Freundlish equation,and adsorption of pyraclofos varied with the different properties of the soils tested.The K_f valves increased with increasing organic matter and clay%.(3)A novel method was developed to simultaneously separate the enantiomers of Rae-pyraclofos using high performance liquid chromatography(HPLC).The enantiomers were simultaneously resolved on a Chiralcel OD-H column,with a mobile phase of n-hexane/2-propanol (90/10/,v/v)at a flow rate of 1mL/min and 25℃.(4)The enantiomeric biotoxicity of the two enantiomers of pyraclofos were investigated.The pure enantiomers of pyraclofos were studied in their in vitro inhibition toward butyrylcholinesterase and in vivo acute aquatic toxicity to D.magna.The in vitro assays showed that (-)-pyraclofos were about 15 times more potent to the enzymes than its (+)-form.In contrast,the(+)-enantiomer was 6.0 times more toxic to D. mgnan 24h tests.The toxicity of racemic pyraclofos was intermediate in both in vitro and in vivo bioassays.These results suggest that the biotoxicity of pyraclofos to non-targeted organisms are enantioselective and therefore post the inconsistent of enantiomers in vitro and in vivo.