Rapid determination of fipronil and its metabolites in aquatic products by modified QuEChERS method coupled with UPLC-MS/MS

Fipronil residues pose public health concerns and have raised global attention. To ensure the quality and safety of aquatic products, this study developed a modified QuEChERS method coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for synchronous detection of fipronil and its metabolites in various types of aquatic products, including fish, echinoderms, crustaceans, and molluscs. Based on the chemical properties of the target compounds and the complex matrix of aquatic products, this study focused on optimising parameters such as extraction conditions and the composition and ratio of adsorbents to achieve the best adsorption effect. The samples were extracted with acidified acetonitrile and purified using a mixture of neutral aluminium oxide, N-propylphthalimide, and graphitised carbon black before instrumental analysis. Qualification was performed using the internal standard method. Excellent sensitivity (with a limit of detection ranged from 0.1 to 0.3 µg/kg), satisfactory linearity (r2 ≥ 0.997), good recovery (85.8% − 110.4%) and good precision (intra-day relative standard deviation < 14.1% and inter-day relative standard deviation < 13.0%) were obtained. The method validation results confirmed that this proposed method was convenient, efficient, cost-effective and reliable for the determination of fipronil and its metabolite in actual aquatic samples. Additionally, it has excellent application potential for quantitative analyses and risk assessment of fipronil residues in marine fish samples collected from South China, providing a new detection strategy and technical support for the routine screening of pesticides in aquatic products.