In situ rapid magnetic solid-phase extraction coupled with HPLC-ICP-MS for mercury speciation in environmental water

SiO2 was coated on the surface of Fe3O4 nanoparticles through hydrolyzation of Na2SiO3, and then thiol groups were modified on SiO2 by silanization reaction to form Fe3O4@SiO2-SH sorbents. Due to high affinity between thiol group and mercury, the Fe3O4@SiO2-SH was applied as magnetic sorbent for in situ extraction and stabilization of trace mercury species from natural water. Trace Hg2+ and methylmercury in 500 mL of water sample could be almost recovered with only 60 mg sorbents. Magnetic separation and rapid adsorption equilibrium greatly simplified extraction procedure and shortened analysis time. Solution pH had no obvious effect on mercury recoveries in the range of 3-9. The loaded Hg2+ and methylmercury were readily desorbed with 2.5 mL of 0.5 mol L-1 HCl containing 1% thiourea. The mercury speciation in eluate was acquired by using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The detection limits of the present method for Hg2+ and methylmercury were 1.0 and 0.3 ng L-1, respectively. The recoveries of spiked water samples were in the range of 96%-104% with relative standard deviations varying from 0.2% to 4.2%, showing good accuracy of the method. (C) 2015 Elsevier B.V. All rights reserved.