Aryl diazonium-mediated functionalization of mesoporous silica nanoparticles with acid blue 193 for efficient dispersed solid-phase extraction of trace Chromium (III) from environmental samples

Aryl diazonium chemistry provides a robust and versatile route for covalent surface functionalization. It allows a controlled introduction of functional groups for advanced analytical and separation applications. In this work, the strategy was applied to graft Acid blue 193 (AB193) onto mesoporous silica nanoparticles (MSNs). The MSNs were synthesized from a sodium silicate precursor using a simple room-temperature sol–gel method, providing an ecofriendly route to porous silica nanoparticles. The resulted stable hybrid nanochelator (MSNs-AB193) was applied as a dispersed solid-phase extraction (dSPE) nanosorbent for the preconcentration of chromium(III) from aqueous samples. Structural and spectroscopic characterizations using Fourier transform infrared spectroscopy (FTIR), elemental analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and brunauer–emmett–teller (BET), confirmed the successfulness of surface modification. Adsorption experiments demonstrated a pronounced pH-dependent uptake of Cr(III), achieving a maximum adsorption capacity of approximately 68 mg g⁻ 1 at pH 5. Equilibrium was rapidly reached within 30 min, and the adsorption kinetics were best described by a pseudo-second-order model. The Langmuir isotherm indicated that the sorption process was dominated by chemisorption. Nearly quantitative recovery (>99%) was achieved using 1.0 M HNO₃ as an eluent. The MSNs-AB193 dSPE method, when coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection, provided an effective and reliable sample-preparation strategy for the determination of Cr(III) in water matrices. The method exhibited excellent analytical characteristics, including wide linearity (R 2 = 0.998), high sensitivity (LOD = 0.007 µg·L⁻ 1 ), and good precision (RSD = 1.73% at 5 µg·L⁻ 1 ). Its accuracy was confirmed through the analysis of ions in EnviroMAT™ groundwater certified reference materials, which produced recoveries of 93–95%. The method was applied to determine chromium concentrations in real groundwater samples from Al-Madinah Al-Munawarah, Saudi Arabia. The measured concentrations ranged from 15 to 17 µg·L⁻ 1 , which are within the World Health Organization (WHO) guideline limits. The sorbent further demonstrated notable chemical stability under acidic to mildly alkaline conditions and retained its extraction performance after more than 10 months of storage.