Analytical Sciences

1-Butyl-3-methylimidazolium Hexafluorophosphate Ionic Liquid as a New Solvent for the Determination of Lead(II) and Cadmium(II) by Anodic Stripping Voltammetry after Extraction of the Iodide Complexes

Akihiro KAMIO and Yukio NAGAOSA

Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Bunkyo, Fukui 910-8507, Japan

The use of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM·PF₆) as a solvent for the anodic stripping analysis of Pb(II) and Cd(II) after extraction of the iodide complexes has been investigated. This method is based on the extraction of the metal iodide complexes into BMIM·PF₆, followed by differential-pulse anodic stripping voltammetry with an in-situ plated bismuth film electrode onto an edge-plane type of pyrolytic graphite substrate. When tetra-n-propylammonium iodide at a concentration of 0.20 mol L^-1 was used as an extractant and a supporting electrolyte, the reduced lead and cadmium produced well-defined anodic peaks at -414 and -736 mV vs. Ag/AgCl, respectively. The peak currents for Pb(II) and Cd(II) were directly proportional to the initial metal concentration in the ranges of 0.01 - 0.50 µg mL^-1 and 0.05 - 1.0 µg mL^-1 under the optimized conditions. A detection limit (S/N = 3) of 0.001 µg mL^-1 Pb(II) was obtained with a volume ratio (V_aq/V_BMIM·PF6) of 2.0 at 300 s deposition time. The relative standard deviation was 3.2% on replicate runs (n = 10) for the determinations of 0.20 µg mL^-1 Pb(II).

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