Dissipation behaviour and risk assessment of fipronil and its metabolites in paddy ecosystem using GC-ECD and confirmation by GC-MS/MS

Abstract

Fipronil -a broad spectrum phenylpyrazole insecticide has high level of toxicity towards environment. Therefore, an easy and reliable analytical method was developed for residue estimation of fipronil to ensure food and environmental safety. A modified QuEChERS technique was followed for estimation of fipronil (5% SC) in paddy ecosystem using GC-ECD and confirmation by GC-MS/MS. The initial residues (0.168–0.794 μg g−1) of total fipronil i.e., sum of fipronil and its metabolites (viz., desulfinyl and sulfone) in leaf and soil were dissipated following first order kinetics. About 92–96% of fipronil residues were degraded after 15 days with half-life of 3.4–4.1 days and pre-harvest interval of 19.4–25.7 days in plant. Residues were below level of quantification (<0.005 μg g−1) in plant and soil at harvest. The fipronil residues in rice grain present low dietary risk (RQd < 1) to human health. However, high risk (RQd > 1) was predicted for cattle health due to fipronil residues in paddy leaf up to 10 days. The residual level in soil was also at highrisk (RQs > 1) for soil ecological health.