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

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%.