Review of recently-developed techniques for analysis of rare-earth elements in geological samples

Rare-earth elements (REE) are increasingly used in other fields besides geology viz. superconductivity and magnets, molecular sieves, etc. The semblance in their geochemical properties besides their occurrence in low-to trace amounts makes it difficult to analyse them by conventional chemical methods and a wide spectrum of analytical techniques have been developed for REE analysis. It has become necessary to review the state-of-art techniques for geological samples. The micro-analytical techniques are not suitable for whole rock or general purpose in view of the small area of sample analysed. Amongst the methods, instrumental neutron activation analysis can detect ultra-trace amounts but of a selective few REE only besides requiring a nuclear reactor. The mass spectrometry type of inductively coupled plasma (ICP) is ideal for REE purpose but equipment cost is much higher than the emission spectrometry which is currently better suited for bulk REE analysis. (author). 33 refs., 1 tab