Study On Residure Dynamics Of Avermectin And Beta-Cypermethrin In Cabbage And Soil And Photolysis Of Avermectin In Aqueous Solution

Residues analytical methods of Avermectin and Beta-Cypermethrin in cabbage and soil were established. Dissipation and the terminal residues of Avermectin and Beta-Cypermethrin in cabbage and soil, as well as photochemical degradation of Avermectin in aqueous solution, were studied in this paper.Residues of Avermectin were extracted from cabbage with acetic ether, while residues of Avermectin were extracted from soil with acetonitrile and water, and determined by HPLC(FLD). The limit of detection of Avermectin (LOD) was 0.1ng and the method detection limit (MDL)of Avermectin in the samples of cabbage and soil was 0.002mg/kg.The average recoveries and coefficient of variations of the method were 77.74 ~ 90.32%,1.50-4.78% for soil samples ,and 75.68 ~ 84.52%, 1.98-3.18% for cabbage samples, respectively. These results showed that the method accords with demands of residue analysis of pesticides.Residues of Beta-Cypermethrin were extracted from cabbage with acetonitrile, while residues of Beta-Cypermethrin were extracted from soil with acetonitrile and water, cleaned up with florsil and determined by GC-ECD. The limit of detection of Beta-Cypermethrin (LOD) was 0.01ng and the method detection limit (MDL) of Beta-Cypermethrin in the samples of cabbage and soil was 0.01mg/kg.The average recoveries and coefficient of variations of the method were 86.37~104.66%,3.51~ 4.53% for soil samples ,and 96.55~114.86%, 2.96~6.61% for cabbage samples, respectively. These results showed that the method accords with demands of residue analysis of pesticide.With the mentioned method, dissipation dynamics and the terminal residues of Avermectin and Beta-Cypermethrin in cabbage and soil had been studied in Anhui and Beijing during 2007 and 2008.The results showed that the dissipation halflife of Avermectin in soil in Anhui in 2007 was 1.98 d ; the dissipation halflife in cabbage was 2d ; the dissipation halflives of Avermectin in soil in Anhui and Beijing in 2008 were 1.06d,1.55d, respectively ; the dissipation halflives in cabbage were 0.94d,1.14d, respectively ; the dissipation halflife of Beta-Cypermethrin in soil in Anhui in 2007 was 3.28d; the dissipation halflife in cabbage was 3.77d; the dissipation halflife of Beta-Cypermethrin in soil in Anhui and Beijing in 2008 were 7.52d, 10.98d, respectively.; the dissipation halflives in cabbage were 4.73d,3.07d, respectively. The terminal residues of avermectin in both cabbage and soil were less than LOQ ; The terminal residues of Beta-Cypermethrin in cabbage were lower than the MRL in china and Japan (2.0 and 1.0 mg / kg , respectively).Photochemical degradation of Avermectin in aqueous solution followed the first order reaction. The results showed that the photodegradation rate of Avermectin under UV lamp irradiation was quicker than under high pressure mercury lamp(HPML) irradiation. The photolytic degradation rate of Avermectin decreased with the initial concentrations increasing and with the pH value decreasing. SDS,nitrate and pigments exhibited photoquenching effects on the photolysis of Avermectin, the photoquenching effects increased with the concentrations increasing of SDS and nitrate.