Thiol-functionalized silica microspheres for online preconcentration and determination of mercury species in seawater by high performance liquid chromatography and inductively coupled plasma mass spectrometry

Abstract

Thiol-functionalized silica microspheres (SH–SiO₂) were prepared from aminosilica by usage of 3-mercaptopropionic acid for online mercury preconcentration. The adsorbent offered adsorption capacities of 27.4 mg g⁻¹ for Hg²⁺, 62.1 mg g⁻¹ for MeHg and 59.6 mg g⁻¹ for EtHg. The enrichment could be directly performed without any column preconditioning, where commonly coexisting ions in seawater and sample pH (1.0–9.0) as well as the sampling flow rate caused no significant adverse effects. The adsorbed Hg-analytes (Hg²⁺, MeHg and EtHg) could be readily eluted (less than 20 s) from the surface of SH–SiO₂ with 60 μL of 100 mM L-cysteine (Cys) + 0.1 M HCl. Hence the enrichment factors of 830 for Hg²⁺, 916 for MeHg and 883 for EtHg were obtained using 5 mL sample in a 35 s enrichment procedure. The detection limits for Hg²⁺, MeHg and EtHg were 0.019, 0.013 and 0.014 ng L⁻¹, respectively, and the relative standard deviations of peak height and peak area were all below 4% for 5 ng L⁻¹. Mercury speciation in ten seawater samples was then analyzed by the proposed method, giving rise to satisfactory spiking recoveries (90–102%).