Hexafluorophosphate ionic liquid-modified silica sorbent for selective separation and preconcentration of Pb2+, Cd2+, and Cr3+ in water samples

Abstract

A sorbent based on ionic liquid-modified silica has been developed for the determination of Cd²⁺, Pb²⁺, and Cr³⁺ in water. Five materials, namely DL1@SiO₂ to DL5@SiO₂, were prepared from five ionic liquids, including N,N,N-trimethyl-N-hexadecylammonium and N-alkylpyridinium hexafluorophosphate, which were grafted onto silica gel. These materials were used to enrich the trace concentration of three metallic cations (Cd²⁺, Pb²⁺, and Cr³⁺) in water samples, followed by the ICP-MS analysis. Among these sorbents, DL1@SiO₂ showed highly efficient sorption. The detection limit of this method for Cd²⁺, Pb²⁺, and Cr³⁺ was 0.173 μg L⁻¹, 0.046 μg L⁻¹, and 0.185 μg L⁻¹, and the relative standard deviation (RSD) was 4.9%, 3.4%, and 1.2%, respectively. The procedure was applied to determine Cd²⁺, Pb²⁺, and Cr³⁺ contents in a spiked tap water sample (Ho Chi Minh City) with satisfactory recovery from 74 to 100.8%.