Identification and Characterization of Impurities in Fipronil Insecticide by LC–MS/MS and NMR

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RATIONALE: Agrochemicals are vital for modern agriculture, ensuring high yields and effective pest control. For high-demand products, impurity profiling is crucial, as even trace contaminants can pose serious health and environmental risks. This study analyzes fipronil impurities using advanced techniques to enhance product safety and minimize environmental contamination. METHODS: Impurities in commercial fipronil were separated using high-performance liquid chromatography with a diode array detector (HPLC-DAD, Agilent 1260) at 220 nm on a Phenomenex Luna C18 column (250 × 4.6 mm, 5 μm). Structural elucidation of impurities was performed using liquid chromatography-high resolution mass spectrometry (LC-HRMS) and tandem mass spectrometry (MS/MS) on an Agilent 6545 Q-TOF system with electrospray ionization. Further, impurities were isolated by preparative HPLC (Gemini-NX-5 C18, 250 × 10 mm, 5 μm) and the structures were confirmed using nuclear magnetic resonance (NMR) spectroscopy. RESULTS: ions, allowing precise determination of their exact masses, elemental compositions, and isotopic patterns. Subsequent LC-MS/MS analysis provided detailed fragmentation data to elucidate the structural features of these impurities. Finally, the proposed structures for the studied compounds were confirmed by NMR spectroscopy. CONCLUSION: Comprehensive impurity profiling of the widely used insecticide fipronil is studied which is essential for ensuring safety, efficacy, and regulatory compliance. In this, three impurities were identified and structurally characterized using HPLC, LC-HRMS, LC-MS/MS, and NMR. This analytical strategy effectively confirms product purity and supports quality control and risk assessment in agrochemical formulations. TRIAL REGISTRATION: CSIR-IICT Communication Number: IICT/Pubs./2025/199.