The Research On Determination Methods Of Pesticide Multi-Residues And The Degradation Dynamics In Bitter Gourd And Cucumber

Bitter gourd and cucumber is an important vegetable species in southern China.Pesticide control is the important measure to control the diseases and pests in those two vegetables,and the resulting problems of pesticide residues have been focusing on.An analytical method was established to determine the pesticides that frequently-used in bitter gourd and cucumber with GC-ECD and GC-MS which can provide technical support to pesticides residue and monitoring in bitter gourd and cucumber.With good agricultural practice(GAP),the field trials of pyraclostrobin,dimethomorph,difenoconazole,azoxystrobin were conducted in bitter gourd and cucumber to investigate the dynamic dissipation regular that hoping to provide a scientific basis and reference to using pesticides reasonably and formulating the safety interval for country.The main results are as follows:1.The study estabished the mothods for determination of pesticides residue in bitter gourd and cucumber.The samples were extracted with acetonitrile,and cleaned up with primary-secondary amine(PSA).Pyraclostrobin,difenoconazole,dimethomorph and azoxystrobin were determined with GC-ECD,and chlorpyrifos,chlorothalonil,propiconazole,tebuconazole,acetamiprid and bifenthrin were determined with GC-MS.The separation effect of each target peak was good and it had no interferential peak in managed samples.Using the matrix-matched standard solution to correct,the average recoveries of pyraclostrobin ect ten pesticides in bitter gourd were at the range of 74.1%to 106.5%,and the relative standard deviations(RSD)were at the range of 2.9%to 7.8%.Using the same pretreatment and determination method to cucumber,the average recoveries of pyraclostrobin ect four pesticides were at the range of 76.3%to 106.8%,and the relative standard deviations(RSD)were at the range of 2.5%to 6.2%.The average recoveries and the RSD could meet the requirements for pesticide residue analysis.2.The field residual test of pyraclostrobin ect four pesticides in bitter gourd and cucumber were conducted.The test results showed that,pyraclostrobin ect four pesticides in bitter gourd and cucumber conformed to the first-order kinetics equation in two kind crops.The half-lives of four pesticides were 2.4～2.6 d and 2.3 d,1.6～2.1 d and 2.1～2.5 d,1.1～2.0 d and 1.9～2.4 d,1.5～2.6 d and 1.8～2.2 d respectively.In the final residue test,the four pesticides’concentrations were all less than the maximum residue limit(MRL)in cucumber(the MRLs of pyraclostrobin,difenoconazole,dimethomorph and azoxystrobin were 0.5 mg/kg,1 mg/kg,5 mg/kg and 0.5 mg/kg respectively).In addition,the study compared the residue in bitter gourd to cucumber.In case of consulting cucumber,the dissipation and the final residue of four pesticides in bitter gourd were similar to cucumber,that were not out of limit.So when planting bitter gourd,using pesticides could consult the cucumber’s.It was reasonable.3.On the basis of the method of pesticide residue determination,market monitoring of pyraclostrobin,difenoconazole,dimethomorph,azoxystrobin chlorpyrifos,chlorothalonil,propiconazole,tebuconazole,acetamiprid and bifenthrin was carried out.Sampling inspection was conducted for three consecutive months in the markets of Sitang,Wutang(the producing area of bitter gourd in Nanning)and Nanning downtown.The monitoring results showed that the detection rates were between 2.8%-30.6%and the concentration were between<0.01-0.21 mg/kg.