Residual characteristic analysis of imidacloprid and chlorothalonil in calabash and cucumber in field and greenhouse

The decline of imidacloprid and chlorothalonil in calabash leaf and cucumber and residue in calabash and cucumber in field and greenhouse were studied by high performance liquid chromatography(HPLC) and gas chromatography(GC) respectively.The reason of residual diversity was analyzed considering meteorological factors.Imidacloprid was extracted with acetonitrile and hydrochloric acid,cleaned up with neutral alumina and florisil,and detected by HPLC-UV.Chlorothalonil was extracted with acetonitrile,cleaned up with neutral alumina,and detected by GC-ECD.The results showed that imidacloprid decline rapidly in both calabash leaf and cucumber.At 7 days after application,the decline rate of imidacloprid in calabash leaf in greenhouse and field were 90.4% and 98.7%,and that in cucumber were 67.8% and 85.9%.However the decline of chlorothalonil in calabash leaf was lower than cucumber.At 7 days after application,its residue on the calabash leaf were 38.1% and 15.4%,while with 87.8% and 91.5% decline rate in greenhouse and in field on cucumbers.It turned out that the decline of two pesticides in these two vegetable in field were both faster than that in greenhouse and the zero residues from the crops in field were lower than that of in greenhouse.It's proposed that the rainfall may be the main factor which caused the diversity of residual decline rate of two kinds of pesticide in field and greenhouse.