Trace Hg speciation and preconcentration by a flow analysis system using an ionic liquid-graphene-Ni foam hybrid material

CRUZ SOTOLONGO, ANNALY; MARTINIS, ESTEFANIA MABEL; MESSINA, MARÍA M.; IBAÑEZ, FRANCISCO J.; WUILLOUD, RODOLFO G.

Águas de Lindóia

Encuentro; 5º ENCONTRO BRASILEIRO SOBRE ESPECIAÇÃO QUÍMICA; 2017

Universidade Estadual Paulista

Mercury is a toxic, persistent pollutant that bioaccumulates and biomagnifies through food chains. Potential health risks from low levels of Hg are a subject of intense debates and the accurate determination and speciation analysis at trace levels is a current analytical challenge. Solid phase microextraction (μSPE) is a widely used technique for the pretreatment of environmental samples due to its high recovery, short extraction time, high enrichment factor, low solvent consumption and ease of automation (1). Moreover, the formation of hybrid nanomaterials based on the functionalization of graphene with ionic liquids (ILs) offers a unique opportunity to modify the physical and chemical characteristics of the nanomaterial (2), turning it into an efficient sorbent for μSPE.In this work, a new hybrid nanomaterial consisting in graphene supported on Ni foam (FG) followed by its functionalization with an IL for the determination of Hg species is proposed. The capabilities of different phosphonium-ionic liquids (PILs) to functionalize graphene were evaluated (3). PILs containing the tetradecyl(trihexyl)phosphonium cation but different anions (dicyanamide and decanoate) and trihexyl(tetradecyl)phosphonium chloride were studied. The hybrid nanomaterial was used as a sorbent in an on-line µSPE system. The inorganic Hg species (InHg) was selectively retained into a column filled with FG-IL material through the formation of a chlorocomplex (HgCl42-) and ion pair formation with the IL cation. The Hg retained into the column was then reduced with SnCl2 to allow its elution and subsequent detection by cold vapor generation coupled to atomic fluorescence spectrometry (CV-AFS). Total concentration of OrgHg was evaluated by difference between the total concentration of Hg and InHg because OrgHg species (MeHg+, EtHg+ and PhHg+) were not retained on the sorption nanomaterial. The effects of various parameters defining the efficiency of the microextraction and detection system (sample and elution flow, sample volume, instrumental conditions, etc.) were investigated. A 100% extraction efficiency was achieved for InHg. The detection limit obtained for the preconcentration of 100 mL of sample was 8.6 ng Hg L-1. The relative standard deviation (RSD) was 3.1% (at 1 µg L-1 InHg and n=10) calculated from the peak height of the absorbance signals (Gaussian form and reproducible peaks). This work reports the first application of a hybrid nanomaterial made of IL-supported graphene-coated Ni foam in an on-line µSPE system for the determination of Hg species in mineral, tap and river water samples.References[1]Płotka-Wasylkaa, J.; Szczepańskaa, N.; De la Guardia, M.; Namieśnika, J.; TrAC Trends in Analytical Chemistry 2016, 77, 23?43[2]Yan, W; Huang, Y.; Xu, Y.; Huang, L.; Chen, Y.; Nanosci Nanotechnol. 2012, 12, 2270.[3]Escudero, L.B.; Olsina, R.A.; Wuilloud, R.G.; Talanta 2013, 116, 133.