溶媒抽出/ICP-AESによるコバルト-クロム-モリブデン合金中微量ニッケルの定量

摘要

In order to determine trace amounts of Ni in Co-Cr-Mo(CCM) alloys, the authors investigated a separation and pre-concentration procedure using liquid-liquid extraction. After acid decomposition of CCM samples, Cr was removed by volatilization as chromyl chloride, and then the residue was dissolved in a 9M HCl solution. Next, the solution was transferred into an extraction funnel with a mixture of 4-methyl-2-pentanone and tri-n-octyl amine, where Co and Mo were removed by the extraction method. Finally, trace amounts of Ni staying in the aqueous phase were determined by ICP-AES. In using the proposed method, all of matrix elements were removed more than 99 % ， and Ni could be quantitatively collected. The limit of quantitation(LOQ) of Ni was 0.01% when quantification by ICP-AES was conducted without the separation and pre-concentration procedure, whereas the LOQ was obtained to be less than 0.0006 % by using the proposed method. Furthermore, the authors applied the proposed method to the analysis of CCM alloys containing 0.01 or 0.2 % of Ni, indicating that the analytical results agreed with each other using several analytical lines of Ni, mainly because little spectral interference occurred.%Co-Cr-Mo(CCM)合金を酸で分解した後，コバルト,クロム及びモリブデンを除去し，微量に含有しているニッケルのみを分離•濃縮する手法を開発した.クロムは過塩素酸を用いて6価に酸化した後，濃塩酸を滴下して塩化クロミルとして揮散除去した.続いて9M塩酸に溶解したコバルトとモリブデンは4-メチル-2-ペンタノン-トリ-n-オクチルアミン溶液で抽出除去し，水相に抽出分離•濃縮した分析対象元素であるニッケルを誘導結合プラズマII光分光分析法(ICP-AES)で測定した.本法によりマトリックス元素であるコバルト，クロム及びモリブデンは99%以上除去され，ニッケルは定量的に回収された.また本法の定量下限は0.0006%以下と，酸分解後直接ICP-AESで測定する場合の定量下限0.01%より向上した.本法をニッケル含有率0.01%及び，0.2%程度のCCM合金試料について適用したところ，ニッケル発光線への分光干渉が除かれ良好な定量結果を得られた.