Thiol-Modified Magnetic Silica Sorbent for the Determination of Trace Mercury in Environmental Water Samples Coupled with Cold Vapor Atomic Absorption Spectrometry

Core-shell magnetic silica has been prepared and then chemically modified with thiol groups. It was used for magnetic solid phase extraction (MSPE) of trace Hg2+ from environmental samples, followed by its determination by cold vapor atomic absorption spectrometry (CV-AAS). The parameters for MSPE procedure, such as pH, elution conditions, ultrasonic time, and effects of co-existing ions were investigated. The results showed that Hg2+ ions are adsorbed on the thiol-modified magnetic silica at pH 6.0 after a 10-min ultrasonic treatment and were quantitatively eluted with 5.0mL thiourea (2%, m/v) in nitric acid solution (0.1M) after a 2-min ultrasonic treatment. Under the optimized experimental conditions, the adsorption capacity of the new sorbent was 101.0mgg1 for Hg2+. The detection limit of the proposed method was 0.06ngmL1 for Hg2+ and the enrichment factor was 16.6. The analytical data obtained from a certified reference water sample (GBW00809) were in good agreement with the certified value. The method has also been successfully applied to the determination of trace Hg2+ in rain water, well water and treated water from a sewage treatment plant. The recovery of Hg2+ from spiked samples was between 96.0% and 110.0%.