Abstract
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.
