Development and validation of a copolymerized thiol-silica based DGT technique for the assessment of bioavailable...

Arsenic (As), particularly in its bioavailable species of inorganic As(Ⅲ) known for its significant toxicity and mobility, is a carcinogenic risk to humans. Serving as an innovative analytical tool, the diffusive gradients in thin films (DGT) technique facilitates on-site detection of bioavailable metals. However, the options of DGT binding gels tailored for As(Ⅲ) detection remain elusive. This study undertook the modification of tetraethyl orthosilicate with a 3-mercaptopropyl-trimethoxysilane to synthesize cost-effective nanomaterials endowed with the capacity for selective adsorption of As(Ⅲ) through copolymerization and atmospheric pressure drying. The synthesized materials were systematically characterized using X-ray diffraction, scanning electron microscopy, and C/H/N/S elemental analysis, revealing a specific surface area of 472.39 m²/g, a particle size of 12.7 nm, and a loading capacity of 3.115 mmol/g. The DGT combined with gel prepared from this material has a specific affinity for As(III) without adsorbing As(V).Its adsorption efficiency for As(III) may reach 84.5% within the first hour. This DGT technique has a linear detection range of 0.5-15 mg/L (R² = 0.99995), an elution recovery of 85.1%-102.7% (RSD < 10%, n = 3), and a maximum adsorption capacity of 301.7 μg/cm², meeting requirements for long-term environmental monitoring. The experiment studied the effects of interfering factors, including pH values ranging from 3-9, ionic strength of 10-500 mmol/L NaNO₃, Fe²⁺ 0-5.0 mg/L, Mn²⁺ 0-1.0 mg/L, As(V) 0-5.0 mg/L, dissolved organic carbon 0-20.0 mg/L, SO₄²⁻ 0.55-1.10 g/L, and PO₄³⁻ 5.0-10.0 mg/L. The device maintained a stable treatment performance under all these conditions. When the DGT device was deployed in spiked river water, estuarine water, and seawater, a comparison of its adsorption performance with existing methods showed that the device had a comparable adsorption performance and demonstrated excellent long-term stability in practical water environment applications.