Mixtures of the protic ionic liquids trioctylammonium bis(trifluoromethanesulfonyl)amide ([TOAH][NTf 2 ]) and trioctylammonium nitrate ([TOAH][NO 3 ]) were investigated as extractants for platinum-group elements. The mixture of 10 wt % [TOAH][NO 3 ] in [TOAH][NTf 2 ] has low viscosity (274.2 mPa s) and low aqueous solubility (2.6 Â 10 À5 mol dm À3 as the cation). With the ionic liquid mixture, Pd(II) and Pt(IV) were extracted almost quantitatively from 0.10 mol dm À3 hydrochloric acid. Under the same conditions, Na(I), Mg(II), K(I), Ca(II), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ru(III), Rh(III), and Cd(II) were only slightly extracted. It was found that the extraction of Pd and Pt increases with increasing content of [TOAH][NO 3] in the mixture. The metals could be back-extracted from the ionic liquid mixture with nitric acid solution, and selective stripping of Pt was possible by controlling the concentration of nitric acid. The metal extractability of the ionic liquid mixture after the back-extraction was equivalent to that of the fresh mixture, indicating that the species composition of the mixture returned to the original state through the back-extraction process. This extraction system provides an efficient separation method for Pd and Pt in acidic chloride media using ionic liquid mixtures, which are recyclable, easy to handle, safe, and environmentally friendly.

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1The 36 Cl/Cl ratios of groundwater samples were measured by AMS in order to investigate 2 the potential use of 36 Cl as a dating tool for modern groundwater. Groundwater samples were 3 obtained from several piezometers in the Oderbruch in northeastern Germany. The shallow 4 confined aquifer of the area is mainly recharged by the infiltration from the River Oder. From 5 the results of measurements, the pre-bomb and the recent background 36 Cl/Cl ratios in the basin 6 of the Oder were estimated to be 7-9 × 10 −14 . The 36 Cl fallout values estimated from the 36 Cl/Cl 7 ratios of the Oderbruch samples, which were dated by the 3 H/ 3 He method, show good agreement 8 with Dye-3 ice core data. These results suggest that the distribution of 36 Cl in groundwaters 9 reflects the influence of the 36 Cl bomb pulse. This, in turn, suggests that the distribution of 10 36 Cl/Cl in modern groundwaters could reveal groundwater ages and flow systems in a region. 11 12 PACS: 92.40.Kf; 91.67.Qr; 93.30.Ge; 06.60.Ei 13

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