Directly-thiolated graphene based organic solvent-free cloud point extraction-like method for enrichment and speciation of mercury by HPLC-ICP-MS

Directly-thiolated graphene (G-SH) was prepared by substitution of the epoxy and hydroxyl groups with mercapto on the bulk and edge of the graphene oxide. Cloud point extraction-like method (CPEL) was established for enrichment of divalent mercury (IHg) and monomethylmercury (MMHg) in the water samples, based on the prepared G-SH, with good hydrophilicity, strong affinity towards mercury species and huge surface area. The large amount of active adsorption sites, thiol groups, on the bulk and edge of the surface of the G-SH play a key role in extraction of mercury species. Under the optimal conditions, the enrichment factors were 78 and 77 based on only 40 mL samples, the detection limits (3δ) by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) were 3.8 and 1.3 ng L− 1 for IHg and MMHg with good recoveries, respectively. The proposed CPEL-HPLC-ICP-MS method was successfully applied for speciation of mercury in surface water, underground water, domestic sewage and even sea water; moreover, the results suggested that it is a simple, sensitive and environment-friendly technique for speciation of mercury at trace levels.