Residue Analysis and Dissipation Study of Dinotefuran in Paddy Field Using a UHPLC-MS/MS Method and Risk Assessment

Dinotefuran is widely utilized to control sucking insect pests in rice crops due to its high efficiency and relatively low hazard potential. However, repeated applications within a single crop season raise concerns about residue deposition in plants and surrounding environment. Therefore, the current study was executed to understand the degradation of foliar sprayed dinotefuran in paddy field after one, two and three application frequencies in a modified QuEChERS method and analysis using UHPLC-MS/MS. The method was linear with corresponding correlation coefficient (R2) > 0.99. The method achieved recovery rates of 78.11-109.30 % in plant matrices and 70.93-75.50% in soil matrices at spiking concentrations of 0.01, 0.05 and 0.10 µg g⁻¹. Precision, expressed as repeatability (RSDr), ranged from 1.99-6.99 % in plant matrices and 1.09-4.06 % in soil matrices and intra-laboratory precision expressed as Horwitz ratio (HorRat) was within 0.3. In the field trial, 500 g of soil samples, 200 g of paddy leaf, grain and straw samples were collected from each replicate for analysis. Soil samples were collected from 0-15 cm layer, while, healthy leaf, grain and straw samples were collected from at least 10 sites per plot. Dinotefuran showed rapid dissipation rates in rice, with half-lives ranging from 1.62 to 2.21 days in leaves and 7.05 days in grains after different application frequencies. No residues were detected in the soil samples regardless of the application frequencies from the 0th day itself. Significant differences in residue levels were not observed among different application frequencies attributed to similar environmental conditions during the growing period. As residues in leaves were below the maximum residue limit on the initial day of application, no waiting period is recommended. All harvested samples were free of residues. Dietary risk assessment indicated that the risk quotient values were below 1, suggesting low risks for consumers.