Residue and decline dynamics of spinetoram in paddy water, soil and rice straw

The residual dynamics of two main components (XDE-175-J and XDE-175-L) of spinetoram in paddy water, soil and rice straw were measured by ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The soil and rice straw samples were extracted with acetonitrile,cleaned up with PSA sorbent and analyzed by UPLC-MS/MS. The water samples were diluted with 0.1% formic acid solution-acetonitrile and analyzed by UPLC-MS/MS. The limits of detection (LODs) of XDE-175-L and XDE-175-J in paddy water, soil and rice straw were 2.5×10-4 mg/L, 5.0×10-4 mg/kg and 0.001 mg/kg, respectively. The limits of quantification (LOQs) in paddy water, soil and rice straw were 0.001 mg/L, 0.002 mg/kg and 0.005 mg/kg, respectively. When the fortification level of XDE-175-L and XDE-175-J ranged from 0.001 to 0.5 mg/kg(L), the average recoveries of two compounds varied from 83% to 102% with the relative standard deviation of 1.9% to 6.2%. The rice was sprayed with 6% spinetoram suspension concentrate(SC) at dosage a.i. 40.5 g/hm2 (one time) at shooting stage of rice, the half-lives of spinetoram residue were 0.35 d, 6.8 d and 1.1 d in paddy water, soil and rice straw, respectively. The dissipation rate was over 95.0% in paddy water and rice straw and over 86.1% in soil at 21 d after application. In conlusion, spinetoram belongs to the easily degradable pesticide type.