Analytical Sciences

Organic Ion-associate Phase Extraction/Back-microextraction for the Preconcentration and Determination of Lithium Using 2,2,6,6-Tetramethyl-3,5-heptanedione by Liquid Electrode Plasma Atomic Emission Spectrometry and GF-AAS in Environmental Water

Kenta MIZUNA,* Ryo MURASHIMA,* Takuya OKAZAKI,* Kazuto SAZAWA,* Hideki KURAMITZ,* Shigeru TAGUCHI,* Keiko NAKAYAMA,** Tamotsu YAMAMOTO,** Yuzuru TAKAMURA,*** and Noriko HATA*

*Department of Environmental Biology and Chemistry, Graduate School of Science and Engineering (Science Div.), Toyama University, 3190 Gofuku, Toyama, Toyama 930-8555, Japan
**Micro Emission Ltd., Ishikawa Create Lab, 2-13 Asahidai, Nomi, Ishikawa 923-1211, Japan
***School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan

We developed an ion-associate phase (IAP)-extraction/acid back-extraction system for the preconcentration and atomic spectrometric determination of lithium trace amounts in water. The chelating reagent for lithium also works as a constituent of the extraction phase. The lithium in a 10 mL sample solution was converted through a chelate complex reaction with 2,2,6,6-tetramethyl-3,5-heptanedione (HDPM). The addition of a benzyldimethyltetradecylammonium ion caused the formation of IAP suspension in the solution. Centrifugation of the solution led to the isolation of a liquid organic phase and the lithium complex was extracted as the upper phase from the centrifuge tube. After the aqueous phase was removed, lithium was back-extracted with a 400 μL nitric acid solution from the IAP. The acid phase was measured using liquid-electrode-plasma atomic-emission-spectrometry (LEP-AES) or graphite-furnace atomic-absorption spectroscopy (GF-AAS). The detection limits were 0.02 mg/L for LEP-AES and 0.02 μg/L for GF-AAS. This system was applied to the determination of environmental water. The HDPM in the organic phase was reusable.

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