High preconcentration of ultra-trace metal ions by liquid–liquid extraction using water/oil/water emulsions as liquid surfactant membranes |
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Authors: | Yasuaki Okamoto Yoshitaka Nomura Hiderou Nakamura Kazuyuki Iwamaru Terufumi Fujiwara Takahiro Kumamaru |
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Affiliation: | a Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, Higashihiroshima 739-8526, Japan;b Department of Life Science, Yasuda Women's Junior College, Yasuhigashi, Asaminamiku, Hiroshima 731-0153, Japan |
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Abstract: | A high preconcentration method by liquid–liquid extraction using liquid surfactant membranes was developed. The water-in-oil (w/o) emulsion containing dilute hydrochloric acid, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate (PC-88A), liquid paraffin, and kerosene was used for the extraction. In a resulting volume of 1000 cm3 of an aqueous sample solution (pH 5.0) containing less than 1 mg of each metal ion, 2 cm3 of w/o emulsion droplets coated with sorbitan monooleate were dispersed. The analyte metal ions in the outer bulk aqueous phase were extracted into the organic phase to form a complex with PC-88A and successively back-extracted into the inner aqueous phase. The analytes in the resulting inner aqueous phase were determined subsequently by graphite furnace atomic absorption spectrometry applied as a detector. By this procedure, concentration factors of 570, 820, 750, 970, 860, and 880 were achieved for chromium(III), manganese(II), cobalt(II), nickel(II), copper(II), and cadmium(II), respectively, and also the respective detection limits (3σ) of 0.4, 20, 1.2, 18, 18, and 0.7 pg cm−3 were obtained. |
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Keywords: | Liquid– liquid extraction PC-88A Liquid surfactant membranes High preconcentration |
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