DETERMINATION OF RARE-EARTH IMPURITIES IN TERBIUM AND TERBIUM OXIDE BY HPLC ICP-AES

A method for the determination of rare earth impurities in terbium and terbium oxide by inductively coupled plasma atomic emission spectrometry interfaced with high performance liquid chromatography (HPLC/ICP-AES) has been studied. The rare earth impurities were separated from terbium for 10 min using a silica-octadecyl column with a eluent of 2-hydroxyisobutyric acid aqueous solution by a concentration gradient method. Not only the mutual separation of the impurities were satisfactory, but the rapid elution gave sharp peaks and sensitive detection. Up to 30-mu-l of a l g/100 ml solution of terbium was able to be injected into the column. By decreasing the radio frequency power in ICP-AES to 0.8 kW, the signal-to-background ratio was increased more than 5 times that with the usual power, 1.3 kW. In the proposed method, the recoveries of rare earth impurities in terbium oxide were 85 approximately 100%. An expensive terbium oxide was not required as a matrix matching standard in this procedure.