The Study On Degradation Of Carbosulfan To Carbofuran In Pakehoi

Carbosulfan as one of the main varieties of carbamate pesticides, its metabolites carbosulfan and carbofuran are very toxic which will threaten the health of both humans and the environmental. Therefore, the regularity of residue degradation of carbosulfan and carbofuran were investigated which were propitious to apply it and introduce to farmers.In this paper, we chose the widely planted and highly consumed Pakchoi as the main objects of this study. The multi-residue of carbosulfan, carbofuran and3-hydroxycarbofuran in Pakchoi and water were also determined. The storage conditions such as light and temperature were used to investigate the stability of carbosulfan in acetone and water; the greenhouse simulation was used to investigation the change trends and degradation ratio of carbosulfan, carbofuran and their metabolites in Pakchoi. The main results of this study are in the following:(1) The compounds were extracted by acetonitrile, and clean-up by Acidic Alumina or Florisil cartridge, detected by GC-NPD, the linear correlation of standard curve was on an satisfactory level, the minimum detection limit of carbosulfan and carbofuran was0.01mg/kg, which was0.02mg/kg for3-hydroxycarbofuran. The average recoveries of carbosulfan, carbofuran and3-hydroxy carbofuran in Pakchoi and water were81.88%～98.44%and75.86%～91.55%with the relative standard deviations of2.17%～5.51%and2.97%～8.87%, respectively. All this showed that the method can meet the detection requirements of pesticide residues.(2) The effect of storage conditions (light and temperature) on the stability of carbosulfan in acetone and water were studied. The results showed that carbosulfan had high stability under the conditions of dark or indoor natural light, while the temperature keep in15℃～25℃, and the degradation effect was also poor in2h. Additionally, in order to ensure the accuracy of the analytical results, both the indoor and outdoor experiments are in accordance with the conditions described above.(3)The dynamic digestion in field trials showed that the average half-life of carbosulfan was0.75d in Pakchoi with sprayed carbosulfan, the average half-life of carbofuran was2.59d in Pakchoi with sprayed carbofuran, and the average half-life of carbosulfan was0.99d d in Pakchoi with sprayed both carbosulfan and carbofuran. The degradation rate of carbosulfari was found to be fast. The concentration of carbofuran and3-hydroxycarbofuran were increased with the time at first and then decreased.(4)According to the data obtained from the above experiments, we can draw a preliminary conclusion:when the ratio between carbofuran and3-hydroxycarbofuran residue in Pakchoi was greater than1, we can initially identify the use of carbosulfan while this value was less than1, and we can identify this Pakchoi had been applied with carbofuran at least.