Degradation properties and identification of metabolites of 6-Cl-PMNI in soil and water

• 6-Cl-PMNI is stable in room temperature and neutral media.
• Temperature is the main fact which influences the hydrolysis of 6-Cl-PMNI.
• The CC olefinic bond reacted with H2O may be the main hydrolytic mechanism.
• 6-Cl-PMNI can be readily degraded in soil mainly by microbial action.
• The split of C–Cl is proposed as the degradation pathway of 6-Cl-PMNI in soil.

In order to provide the scientific basis for the environmental risk assessment of cycloxaprid and 6-Cl-PMNI (intermediate of cycloxaprid), the degradation properties of 6-Cl-PMNI in aerobic, anaerobic and/or sterile soil, as well as in water with different pH values at different temperature were explored under laboratory conditions using HPLC for its kinetics study and UPLC-MS/MS for the identification of its metabolites/degradation products. Fortification study showed that the recoveries of 71.4–100.5% with the maximum coefficient variation (CV) of 7.47% were obtained. The linear range was 0.1–10 mg/L with the good linearity of R2 = 0.9990. For standard, the method LOD (limit of detection) and LOQ (limit of quantification) was 0.03 mg/L and 0.1 mg/L, respectively. Results demonstrated the good performance of the developed method. Kinetics study indicated that the degradation half-lives (t0.5) in pH 3-pH 10 buffers varied from 111.8 d to 288.8 d at 25 °C but rapidly shortened to 1.6–25.7 d at 70 °C. Good negative linear ships (R2 ≥ 0.8423) between half life and temperature were found. 6-Cl-PMNI could be readily degraded in non-sterile soil (t0.5 0.8–7.5 d) while slowly degraded in sterile soil (t0.5 64.8–91.2 d). Three hydrolytic products and one metabolite of 6-Cl-PMNI in aerobic soil were identified. The CC olefinic bond reacted with H2O by Markovnikov Additive Reaction and the split of C–Cl were mainly proposed as the possible reaction pathway for 6-Cl-PMNI degradation in water and in soil, respectively.

Figure optionsDownload as PowerPoint slide