Determination of trace impurities in tantalum by inductively coupled plasma mass spectrometry after removal of the matrix by liquid-liquid extraction

Trace impurities in tantalum have been isolated by extracting the tantalum matrix from aqueous solutions containing hydrofluoric and hydrochloric acid into methyl isobutyl ketone. A study on the extractability of the fluoride complex by methyl isobutyl ketone and diisopropyl ketone indicated that the former was much more effective. The extractability of tantalum was higher in a HCl medium as compared to HNO3. Tantalum was easily extracted into the organic phase while most impurities usually accompanying tantalum, e.g. V, Nb, Zr, Hf and W, remained almost completely in the aqueous phase. Trace impurities were analyzed in the aqueous phase by inductively coupled plasma mass spectrometry (ICP-MS) after evaporating the excess acids. The detection limits for most impurities in tantalum were in the sub-μg/g range. The procedure could be applied to the determination of spallation products in a tantalum target irradiated with 800 MeV proton especially in combination with the sensitive ICP-MS.