Isoprocarb Suspension Dynamics And Safety Evaluation On Rice Residues

Now, human’s food supplies are mainly solved by increasing unit production anddecreasing crop loss from the usage of pesticides and fertilizer. Pesticides playimportant role in protecting crops, defending diseases and insects, improving theenvironment and controlling diseases. Rices are the main food crop in our country, aswell as our province. Total production of rice in2012is204290thousand tons. In ourprovince, it is26890thousand tons, which is Num. One in our country. However, ricedisease and insects are the important factor affecting rice’s production. The sufferingarea is high up to1million Mu every year, which results in the loss rate of up to15~30%. So it is an urgent problem how to effectively prevent diseases and insects anddecrease the loss. In the recent years, the3R (Residue, Resistance, Resurgence)problem has been growing because of the irrational use of pesticides. As the increasingawareness of environmental protection, people have gradually realized the importanceof protecting environment at the same time of killing insects. Therefore, the pesticideswith high potency, low toxicity and low residues are widely used by people.Chemical name of isoprocarb: o-cumenyl methylcarbamate, which belongs to akind of carbamate ester insecticides. This kind of insecticides act by gastric poison, tagkilling and fumigation, which are tag killing drugs with internal absorption. Theinsecticides are soluble in acetonitrile, acetone, and ethyl acetate. They, which can beprepared by the reaction of O-isopropylphenol and isocyanate, are of quick result andshort action time. Its toxicity is from inhibiting cholinesterase’s activity, blockingnormal nerve conduction, further causing the imbalance of the whole physiological andbiochemical process, and until death. isoprocarbinvides the human body throughrespiratory and gastrointestinal systems, as well as is absorbed by mucocutaneouspathway. The pesticide is mainly distributed in liver, kidney, fattiness and musculature, which can be rapidly metabolized after hydrolyzation, oxidation, and combinationreaction with other wastes, finally discharged along with stale.In this paper, we carefully carried out the experimental design ofisoprocarbsuspension in field and, by residue analysis of isoprocarbin rice, rice husk,paddy soil, and rice plant, investigated dynamic elimination of in paddy water, paddysoil and rice plant and harvest time, as well as final residue amount in these cases.Rice, rice husk, paddy water, paddy soil and rice plant were first extracted bywater and acetonitrile, followed by salting out and evaporation of acetonitrile phase,then refined by Florisil SPE and elution of5+95(volume) methanol dichloromethanemixture solution, finally measured by liquid chromatography mass spectrometry afterconcentration to constant volume. The solution was analyzed by WATERS TQD, C18100mm×1.7mm×2um chromatography column. The concentration in the method wasset to be0.005mg/kg,0.20mg/kg. The mean recovery rate in themethod was in76.8~100.1%. The variation coefficient was in1.7~14.3%, whichaccords with analysis need. The actual final test concentration in brown rice, rice husk,paddy soil, and rice plant was0.005mg/kg.By experiments in field and liquid chromatography mass spectrometry analysis,we investigated the dynamic elimination in rice plant, paddy water, and paddy soil andthe final residues amount of isoprocarbsuspension in rice, rice husk, rice plant, andpaddy soil from Harbin of Heilongjiang Province, Zhengzhou of Heinan Province, andNanjing of Jiangsu Province. The results show that the elimination of isoprocarb inpaddy water, paddy soil, and rice plant conforms to the dynamics equation of the firstorder of reaction. The half-time of isoprocarb degradation in rice plant is3.4~4.1d, thehalf-time in paddy water is1.9~5.0d, that in paddy soil is4.3~7.5d.By three and four times administration of isoprocarb in the dose of300a.i.g/ha and one and a half time450a.i.g/ha during the growth of rice, the residues amount ofisoprocarb in brown rice from Harbin, Nanjing, and Zhengzhou are0.005~0.143mg/kg, all of which are lower than0.2mg/kg. The measurement results show thatisoprocarb is easily degraded (T1/2<30d). The most three times administration with thedose of300a.i.g/ha is suggested in the usage of isoprocarbfor rice field, and the timegap between the last administration and harvest should not be shorter than40days.The largest residue amount of isoprocarb in rice (MRL) should be0.2mg/kg.