Determination of rare-earth elements and yttrium in silicate rocks by sequential inductively-coupled plasma emission spectrometry

An ICP—AES method for determination of rare-earth elements (REE) and yttrium at trace levels in silicate rocks is described. The method involves decomposition of the rock sample by heating with a mixture of hydrofluoric and perchloric acid, followed by precipitation of the REE and Y as oxalates, with calcium as carrier. The oxalate precipitate is ignited to the oxide, which is then dissolved in dilute nitric acid and the solution is used for ICP—AES measurements, with use of pure REE solutions as calibration standards. The method has been applied to the determination of REE in a number of standard reference materials and the results have been compared with the reported values. Three other silicate rock samples have also been analysed for REE and Y by this method.