Ionic liquid-immobilized silica gel as a new sorbent for solid-phase extraction of heavy metal ions in water samples

In the current study, we have developed a solid-phase extraction (SPE) method with novel C18-alkylimidazolium ionic liquid immobilized silica (SiO 2 -(CH 2 ) 3 -Im-C 18 ) for the preconcentration of trace heavy metals from aqueous samples as a prior step to their determination by inductively coupled plasma mass spectrometry (ICPMS). The material was characterized by Fourier-transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Energy-Dispersive X-ray Spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) analysis. A mini-column packed with SiO 2 -(CH 2 ) 3 -Im-C 18 sorbent was used for the extraction of the metal ions complexed with 1-(2-pyridylazo)-2-naphthol (PAN) from the water sample. The effects of pH, PAN concentration, length of the alkyl chain of the ionic liquid, eluent concentration, eluent volume, and breakthrough volume have been investigated. The SiO 2 -(CH 2 ) 3 -Im-C 18 allows the isolation and preconcentration of the heavy metal ions with enrichment factors of 150, 60, 80, 80, and 150 for Cr 3+ , Ni 2+ , Cu 2+ , Cd 2+ , and Pb 2+ , respectively. The limits of detection (LODs) for Cr 3+ , Ni 2+ , Cu 2+ , Cd 2+ , and Pb 2+ were 0.724, 11.329, 4.571, 0.112, and 0.819 μg L −1 , respectively with the relative standard deviation (RSD) in the range of 0.941-1.351%. Novel C18-alkylimidazolium ionic liquid immobilized silica (SiO 2 -(CH 2 ) 3 -Im-C 18 ) was synthesized through a four-step procedure. It showed high efficiency for the separation/preconcentration of trace heavy metal ions from aqueous samples.