This study was carried out to identify residual distribution and dissipation pattern of insecticide cyenopyrafen and dinotefuran in eggplant(Solanum melongena L.), and to establish pre-harvest residue limits (PHRLs) based on the dissipation rates and biological half-lives of pesticides residue. Moreover, risk assessment by dislodgeable foliar residues(DFRs) were measured. The studies were conducted in two different greenhouse, located in field 1 (Hwasun, Jeonranam-do) and field 2 (Gwangju, Jeonranam-do), the pesticides were spayed onto the crop at recommended dosage.
Eggplant samples and leaf disk were collected at 0, 1, 2, 3, 5, 7 and 10 days after spraying pesticides. Residuals of cyenopyrafen and dinotefuran were extracted with acetonitrile and partitioned with dichloromethane and hydromatrix, respectively. And then, the residues were analyzed using HPLC-UVD and PDA at 270 and 297 nm after purified with Florisil(5 g, 10 g, 60∼100 messh). For DFRs, leaf disk samples were extracted with surfactant(0.02% sulfosuccinate sodium salt), partitioned with dichloromethane and hydromatrix and analyzed using LC-MS/MS.
For eggplants method validation, MLOQ(Method Limit of Quantification) were 0.02 and 0.02 mg/kg for cyenopyrafen and dinotefuran, respectively. Recoveries for cyenopyrafen and dinotefuran at two fortification levels were ranged 84.0∼103.0% and 80.1∼92.4%, respectively, with <10% coefficient of variation. For DFRs method validation, MLOQ(Method Limit of Quantification) were 0.005 and 0.001 μg/cm2 for cyenopyrafen and dinotefuran, respectively. Recoveries for cyenopyrafen and dinotefuran at two fortification levels were ranged 85.6∼105.0% and 77.8∼97.1%, respectively, with <10% coefficient of variation.
The initial residue in eggplant of cyenopyrafen and dinotefuran was 0.77 and 0.98 mg/kg in field 1 and 0.80 and 0.60 mg/kg in field 2, respectively. The biological half-lives of cyenopyrafen and dinotefuran were 5.7 and 2.8 day in field 1 and 1.9 and 4.1 days field 2, respectively.
For DFRs residue concentration of cyenopyrafen and dinotefuran was 0.075 and 0.94 μg/cm2 in field 1 and 0.028 and 0.70 μg/cm2 in field 2, respectively. The biological half-lives of cyenopyrafen and dinotefuran were 5.1 and 6.6 day in field 1 and 5.4 and 4.7 days field 2, respectively.
Risk assessment of cyenopyrafen and dinotefuran indicates that ADE values are was 0.38 and 3.95 μg/day in field 1 and 0.12 and 2.71 μg/day in field 2 and then MOS values was 7879 and 3341 in field 1 and 25347 and 4867 in field2, respectively. Therefore, the risk of harvester from exposure to pesticides is very low. and eggplant is usually harvested everyday during production period due to its fast growing characteristics. -2.1 ∼ -4.4 days of REI was determined, indicating they could reenter greenhouse on the day of application.