Graphene oxide functionalized with a long chain ionic liquid for preconcentration and determination of Hg in water samples

SOTOLONGO, ANNALY; MARTINIS, ESTEFANIA; LLAVER, MAURICIO; WUILLOUD, RODOLFO G.

Santos

Congreso; 5th IBEROAMERICAN MEETING ON IONIC LIQUIDS (IMIL 2017); 2017

Universidade Estadual Paulista (UNESP)

Graphene is a nanomaterial that is formed by layers of a few atoms thick and has become particularly important because of the wide range of applications found: sensors, electronics and analytical chemistry.1 Functionalization of graphene with ionic liquids (ILs) offers a unique opportunity of altering the physical and chemical characteristics of the nanomaterial. Thus, the presence of functional groups can alter the retention/affinity of the graphene surface and other important properties such as polarity and hydrophilicity.2 Therefore, in this work, the capabilities of oxidized graphene (OG) functionalized with a long chain IL (1-butyl-3-dodecylimidazolium bromide, [C4C12im]Br) were studied to assess if this substrate is an efficient material for Hg(II) preconcentration. A microcolumn filled with the IL-OG nanomaterial was used as part of an on-line preconcentration system coupled to flow injection-cold vapour-atomic fluorescence spectrometry (FI-CV-AFS). Graphene have a marked tendency to aggregate, which negatively affect the hydrodynamic characteristics of the packed column. For this reason, the preparation of the microcolumn was studied in detail. A careful evaluation of the optimum dimensions of the microcolumn and especial characteristics of the filling material were performed. Different materials like feldspar, quartz and glass, were tested to avoid IL-OG compaction. Finally, the microcolumn was filled with a mixture of IL-OG and milled glass, since this material avoid sorbent aggregation and show chemical compatibility with mineral acids used for analyte elution. Concerning column design, the best performance was achieved when packing the substrate in a microcolumn of 2 mm (i.d.) and 1.5 mm length. The effect of chemical and physical parameters including the pH of the solutions, the eluent type and the concentration was systematically examined. Mercury was retained at pH 5.0 and 20% (v/v) HNO3 was the best alternative for Hg(II) elution. The preconcentration system was evaluated for quantitative determination of Hg at trace levels in tap and mineral water samples. The proposed IL-functionalized nanomaterial showed a high Hg retention (87%) without the need of additional organic reagents to form complexes or other derivates, which is an important advantage compared with traditional preconcentration methods.1 Huafeng Yang, Fenghua Li, Changsheng Shan, Dongxue Han, Qixian Zhang, Li Niu and Ari Ivaska, Journal of Materials Chemistry (2009) 19, 4632-46382 Weibo Yan, Yi Huang, Yanfei Xu, Lu Huang and Yongsheng Chen, Nanoscience and Nanotechnology (2012) 12, 2270-2277