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

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 mu L 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%).