Capabilities of ionic liquids as ion pairing agents and extraction solvents for dispersive liquid-liquid microextraction and determination of thallium species in water samples

ESCUDERO, LETICIA B.; BERTON, PAULA; MARTINIS, ESTEFANIA M.; OLSINA, ROBERTO A.; WUILLOUD, RODOLFO G.

Campos Do Jordao

Congreso; 16th ANALYTICAL CHEMISTRY NATIONAL MEETING; 2011

University of Sao Paulo

Thallium (Tl) is a highly toxic element that is used in alloys, low temperature thermometers, dyes, pigments, optical lenses and jewelry. It is well-known that Tl is more toxic than Hg, Pb or Cd and is one of 13 priority metal pollutants listed by the United States Environmental Protection Agency (US EPA). Therefore, its determination is of great interest because of its clinical and environmental implications. Ionic liquids represent an attractive tool for replacing conventional organic solvents in liquid-liquid extraction procedures, reducing volatility, toxicity and flammability drawbacks.2 The aim of this work was the development of a highly sensitive analytical methodology for determination of Tl+ and Tl3+ species, based on the use of modern solvents such as ILs. Initially, Tl+ was complexed with iodide ion at pH 1 in diluted sulfuric acid solution. Then, tetradecyl(trihexyl)phosphonium chloride ionic liquid (CYPHOS® IL 101) was used as ion pairing agent and a dispersive liquid-liquid microextraction (DLLME) procedure was developed by dispersing 60 µL of 1-hexyl-3-methylimidazolium hexafluorophosphate [C6mim][PF6] with ethanol in the aqueous solution. Analyte determination was performed by direct injection of the final IL phase into the graphite furnace of an electrothermal atomic absorption spectrometer (ETAAS). An extraction efficiency of 75% and an analytical sensitivity enhancement factor of 100 were obtained with only 5.00 mL of sample. The limit of detection (LOD) was 3.3 ng L−1 Tl, while the relative standard deviation (RSD) was 4.9% (at 0.5 µg L−1 Tl and n = 10), calculated from the peak height of absorbance signals. The method was finally applied to determine Tl species in tap and river water samples after previous separation of the species with an ion exchange resin. To the best of our knowledge, this work reports the first application of ionic liquids for Tl extraction and separation in the analytical field. 1)Lison, D. In Handbook on the Toxicology of Metals (Third Edition); Nordberg, G. F., Fowler, B. A., Nordberg, M., Friberg, L. T., Eds.; Academic Press: Burlington, 2007, pp 511. 2)E.M. Martinis, E.M.; Berton, P.; Monasterio, R.P.; Wuilloud, R.G. TrAC - Trends in Analytical Chemistry, 29 (2010) 1184.