Matrix Interference Removal Using Fe3O4@SiO2-PSA-Based Magnetic Dispersive Solid-Phase Extraction for UPLC-MS/MS Analysis of Diazepam in Aquatic Products

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A sensitive method was developed for detecting diazepam residues in aquatic products using magnetic dispersive solid-phase extraction (MDSPE) coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples extracted with 1% ammonia-acetonitrile were purified using synthesized Fe₃O₄@SiO₂-PSA nanoparticles via MDSPE before UPLC-MS/MS analysis. Separation was performed on a C₁₈ column with gradient elution using 0.1% formic acid-2 mM ammonium acetate/methanol. Detection employed positive electrospray ionization (ESI⁺) in multiple reaction monitoring (MRM) mode. Characterization confirmed Fe₃O₄@SiO₂-PSA's mesoporous structure with excellent adsorption capacity and magnetic properties. The method showed good linearity (0.1-10 μg/L, r > 0.99) with an LOD and LOQ of 0.20 μg/kg and 0.50 μg/kg, respectively. Recoveries at 0.5-15.0 µg/kg spiking levels were 74.9-109% (RSDs 1.24-11.6%). This approach provides rapid, accurate, and high-precision analysis of diazepam in aquatic products, meeting regulatory requirements.