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

Abstract

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 5.0 mL thiourea (2%, m/v) in nitric acid solution (0.1 M) after a 2-min ultrasonic treatment. Under the optimized experimental conditions, the adsorption capacity of the new sorbent was 101.0 mg g⁻¹ for Hg²⁺. The detection limit of the proposed method was 0.06 n g mL⁻¹ 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%.

Keywords:

• CV-AAS
• Environmental samples
• Magnetic silica
• Magnetic solid phase extraction
• Mercury

Acknowledgments

Financial supports from National Nature Science Foundation of China (No. 21205028), Natural Science Fundamental Research Fund of Science and Technology Department of Henan Province (112300410080), the program for young teachers of universities in Henan province (2012GGJS-300) and Plan for Scientific Innovation Talent of Henan University of Technology (No. 11CXRC11) are gratefully acknowledged.