Preparation of stable thiol-functionalized magnetic nanoparticles for magnetic solid phase extraction of As(III) in environmental waters

Thiol-based materials exhibit good adsorption properties for sulfophilic elements, such as As(III). However, these materials are prone to oxidation in air, leading to poor storage stability, which limits their practical application. To address this problem, using cystamine dihydrochloride (CA) as the functional reagent and glycidyl methacrylate (GMA) modified magnetic nanoparticles (MNPs) as the core, MNPs of Fe₃O₄@SiO₂@GMA-CA was synthesized via an amino-epoxy click chemistry reaction, and the thiol-functionalized MNPs of Fe₃O₄@SiO₂@GMA-CA-SH was obtained after breaking the disulfide bond of CA. The material exhibits great storage stability when preserved in the form of Fe₃O₄@SiO₂@GMA-CA, and the Fe₃O₄@SiO₂@GMA-CA-SH possesses strong magnetism and high adsorption selectivity for As(III). With the use of Fe₃O₄@SiO₂@GMA-CA-SH as the adsorbent, a new method of magnetic solid phase extraction (MSPE) combined with inductively coupled plasma optical emission spectrometry (ICP-OES) was established for the speciation analysis of As(III) and As(V) in environmental water samples. Various experimental parameters affecting the MSPE have been optimized. Under the optimal conditions, the limit of detection (LOD) of the developed MSPE-ICP-OES method was 0.050 μg L⁻¹, the relative standard deviation was 2.8 %, and the enrichment factor was 150-fold. The accuracy of the method was validated through the analysis of the Certified Reference Materials of GBW08666 and GBW08667. The established method was successfully applied to the speciation analysis of inorganic arsenic in potential arsenic-contaminated environmental water samples, demonstrating a great application potential in real-world sample analysis.