The use of pre-irradiation group separations with neutron activation analysis for the determination of the rare earths in silicate rocks

The radiochemical neutron activation technique used consists of five stages; viz. sample digestion, cation exchange chromatography, irradiation and counting. Silicate samples are decomposed using a conventional hydrofluoric/perchloric acid digestion followed by loading the solutions, as chlorides, onto cation exchange resin columns. The columns are eluted with 2M HCl to remove unwanted elements and the rare earth elements are subsequently desorbed with 6M HCI. A tracer,¹⁴⁴Ce, is used to monitor the chemical yields and studies show that no fractionation or loss of any REE occurs. The REE abundances of five reference samples (NIM-G, SY-2, MRG-1, JB-1 and BOB-1) show that the described procedure is capable of providing good accuracy and precision. The method has some advantages over conventional INAA and RNAA and these are described.