On-line solid supported ionic liquid-based dispersive liquid-liquid microextraction coupled to cold vapor atomic absorption spectrometry for inorganic and organic mercury determination in water samples

ESCUDERO, LETICIA B.; OLSINA, ROBERTO A.; WUILLOUD, RODOLFO G.

Foz do Iguaçu

Simposio; TWELFTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY; 2012

TWELFTH RIO SYMPOSIUM ON ATOMIC SPECTROMETRY

Mercury (Hg) is a non-essential toxic element that affects the central nervous system [1]. Discrimination between inorganic (In-Hg) and organic mercury (Org-Hg) species is important as Org-Hg compounds shows higher toxicity than In-Hg species. Ionic liquids (ILs) have no effective vapor pressure, avoiding emission of volatile organic compounds to the atmosphere [2]. These solvents have been applied in several works as a novel alternative in separation science [3]. Among miniaturization techniques, ionic liquid-based liquid-liquid microextraction (IL-LLME) has been applied for metal preconcentration. IL-LLME shows advantages over conventional extraction techniques, since it is fast and easy to operate. However, a practical limitation of IL-LLME is that IL should have higher density than water to achieve straightforward phase separation, thus conditioning the selection of the IL. In the present work, a convenient strategy is presented which allows the use of ILs lighter than water for the development of LLME techniques. In addition, the proposed methodology offers an important advantage regarding minimal consumption of IL. Thus, a novel method based on the use of tetradecyl(trihexyl)phosphonium chloride (CYPHOS® IL 101) ionic liquid, as impregnation reagent supported onto Amberlite XAD-1180 polymeric resin, has been developed for Hg species determination in water samples. Initially, In-Hg [i.e. Hg(II)] was complexed with chloride ions, followed by its introduction into a flow injection on-line system to quantitatively retain the anionic chloro-complex in a column packed with CYPHOS® IL 101-impregnated resin. The trapped Hg was then reduced with stannous chloride (SnCl2) and eluted with the same flow of reducing agent and finally determined by cold vapor-atomic absorption spectrometry (CV-AAS). Organic mercury species (Org-Hg) did not interact with the impregnated resin and were not retained into the column. Consequently, Org-Hg concentration was calculated by subtracting In-Hg from total Hg concentration. A 95% extraction efficiency was achieved for Hg when the procedure was developed under optimal experimental conditions. The limit of detection for preconcentration of 40 mL of sample was 1.9 ng L-1 Hg, while the relative standard deviation (RSD) was 2.7% (at 1 ug L−1 Hg and n=10), calculated from the peak height of absorbance signals. To the best of our knowledge, this works reports the first solid-supported IL-based liquid-liquid microextraction approach implemented in a flow injection on-line system for determination of Hg species in tap and river water samples.1. E. Vereda Alonso, M. T. Siles Cordero, A. García de Torres, P. Cañada Rudner, J. M. Cano Pavón, Talanta, 77:53,20082. L. Ji, S.W. Thiel, N.G. Pinto, Ind. Eng. Chem. Res., 47:8396,20083. D. Han, K. H. Row, Molecules, 15:2405,2010