Solid-Phase Extraction of Trace Cr(VI) in Water Using Polydopamine-Functionalized Silica Core-Shell Composites: Mechanisms and Applications

Trace-level hexavalent chromium in aquatic systems poses serious risks to human and ecological health. Polydopamine-functionalized silica (SiO2@PDA) composites were synthesized and applied in a micro-column format for the solid-phase extraction (SPE) of Cr(VI), followed by its determination by inductively coupled plasma mass spectrometry (ICP-MS). The method exhibited high selectivity for Cr(VI) within a pH range of 1.0–4.0, achieving a detection limit (LOD) of 0.0018 μg/L and a relative standard deviation (RSD) of 4.65% (n = 20). The adsorption mechanism was primarily governed by electrostatic interactions, mesopore entrapment, and hydrogen bonding. To evaluate practical applicability, real water samples were analyzed, yielding satisfactory recoveries ranging from 92.62% to 97.47% for the analyte. This work represents the first application of SiO2@PDA in SPE for the determination of Cr(VI), demonstrating excellent sensitivity, selectivity, and practical applicability for trace chromium speciation in complex aqueous matrices.