Graphene oxide as an efficient adsorbent of solid-phase extraction for online preconcentration of inorganic and organic mercurials in freshwater followed by HPLC-ICP-MS determination.

For the past several decades, lots of adsorbent nanomaterials have been adopted for the enrichment of mercuric compounds. In this paper, graphene oxide bounded silica particles were employed as the absorbent for online preconcentration of Hg(II), methylmercury (MeHg) and ethylmercury (EtHg) by solid phase extraction. The adsorbent offered satisfactory adsorption capacities of 40.7 for Hg(II), 91.4 for MeHg and 103.8 mg g for EtHg. Enrichment conditions such as type, concentration and volume of conditioning and eluting reagents were optimized. The pH, volume and flow rate of sample were also optimized. High enrichment factors (1963, 1881 and 1794 for Hg(II), MeHg and EtHg, respectively) were obtained with 10 mL sample (adjusted to pH 4-7) at 10 mL min flow rate, 5 μL of 10 mM benzoic acid for elution and 4 mL of 1 mM 4-phenyl-3-aminothiourea for preconditioning. The detection limits obtained were downscaled to be 0.005 for Hg(II), 0.006 for MeHg and 0.009 ng L for EtHg with relative standard deviations of all the analytes below 5%. Standard reference material and spiked water samples were analyzed for validating the method with satisfactory recoveries of 89-106%. The present method was successfully applied to determine mercury compounds in drinking water, and river and tap water, in which Hg(II), MeHg and EtHg were presented below the China's drinking standard limit of 1 μg L.