Dynamics of Ethametsulfuron-Methyl Residue in Paddy Soils Revealed by HPLC-MS/MS

Ethametsulfuron-methyl (ESM) was extensively applied for weed control in rape seed, which taking turns with rice. Such farming model was predominant in southern of China and Southeast Asia. However, ESM damages subsequent rotation with rice, and potentially pollutes the environment. Residue of ESM dynamics in paddy soil is still ambiguous. In this study, a modified high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for the detection of traces of ESM residues in paddy soil was developed and validated. Dynamics of ESM residue was performed by laboratory mock and field trial. The limit of detection (LOD) and limit of quantitation (LOQ) of ESM in paddy soil were 1.10 × 10-6 ng and 1.27 × 10-3 ug·kg-1, respectively. At fortification levels of 0.2 and 2 mg·kg-1 in paddy soil samples, the recoveries ranged from 85.56% to 100.16% with relative standard deviations of 7.42-9.69% (n = 5). The dynamics of ESM in laboratory mock trial showed that the half-lives (t1/2) of ESM in paddy soil were over 100, 16.35 and 10.35 days at 6 oC, 25 oC and 35 oC, respectively. The t1/2 of ESM in the field trial was 34.66 days at recommended dose of 18 g active ingredient·ha-1. This work would contribute to safe utilization of ESM.