Analytical Sciences

Determination of Rare-Earth Elements in a Limestone Geological Standard Reference Material by ICP-MS Following Solvent Extraction

Kengo IGARASHI,* Tasuku AKAGI,* Feng-Fu FU,** and Sadayo YABUKI**

*Faculty of Agriculture, Tokyo University of Agriculture and Technology, Saiwai-cho, Fuchu, Tokyo 183-8509, Japan
**Division of Surface Characterization, The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan

Rare-earth elements in a limestone geological standard (JLs-1) were determined by inductively coupled plasma mass spectroscopy (ICP-MS) using phosphoric acid 2-ethylhexyl ester solvent extraction, which had been established for seawater analysis. First, the limestone sample was divided into two fractions: acetic acid soluble (carbonate fraction) and insoluble (residue). A modification of the method was undertaken to achieve quantitative recovery. With this method most of the REEs in the carbonate fraction were quantitatively recovered, except for the heaviest three REEs (Tm, Tb and Lu). The reason for the poor recoveries of the three elements was investigated, but still remained unclear. The massspectroscopic interference of BaO with Eu made an accurate determination of both lighter REEs and Eu at the same time impossible. The precision of this method was better than 20%. The data adopted after analytical consideration were consistent with those previously reported.

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