Abstract
Lutetium, ytterbium and terbium have been determined in some standard rocks from U.S. Geological Survey by neutron-activation analysis. A chromatographic procedure involving anion exchange in a mixed solvent system has been developed to obtain selective separation of the required radioisotopes from other activities induced during the irradiation. Lutetium and ytterbium are eluted in the same fraction, while terbium is obtained in a separate fraction. Chemical yield determination is performed by re-activation. The precision of the method is found to be about ±5 to 15 per cent. for the samples analysed.