Chelex-100キレート樹脂を用いる前処理と誘導結合プラズマ質量分析法による日本近海及び太平洋の海水中インジウムの定量

摘要

Inは，地核中の濃度が重量で0.24ppm という希元素のrn一つである．安定な同位体の質量数は，113と115で，rnこれらの存在比は，それぞれ4.29%,95.71%である．rnIn は，歯科医用の合金,はんだや半導体のための純結晶rnなどに使われてきたが，最近では液晶ディスプレー用にイrnンジウム一酸化スズ（ITO）として使われるようになり，rn急速に需要が増大している．%Recently, the demand for indium (In) is increasing mainly due to its use for electrodes of liquid crystal displays. In is toxic and causes the sickness and vomiting in the case of oral intake. Thus, the determination of In in sea water is important since In is accumulated in marine creatures and is finally taken into human beings. Therefore, the concentration of In in the seawater around Japan and the north eastern Pacific Ocean was measured by inductively coupled plasma mass spectrometry (ICP-MS). As a pretreatment, a Chelex-100 chelating resin method was used. ~(115)In was used for a measurement by MS, and a high background signal was observed when the eluent was heated with hydrochloric acid to vaporize the ammonium ion so as to remove the interference by magnesium and calcium in sea-water samples. This high background is presumably due to Ar_2Cl~+ polyatomic ion because a background intensity was very low when N_2-MIP-MS was used to determine In. However, the high background signal greatly decreased upon heating the solution with HNO_3 (1 + 1) before preparing the final solution for the measurement by MS. The results obtained by the proposed method were compared with those by solvent extraction with APDC-HMAHMDC/xylene, and the results using both methods were in a good agreement with each other. The concentrations of In around Japan were considerably different between the sampling points. However, the results in the Pacific Ocean were almost equal over a wide sea area. The concentration of In (including around Japan and the Pacific Ocean) was in the ranges of 0.08 ～0.72 ng/L and the relative standard deviations of the results were 8.3% ～ 37.5%.