Improvement in the ion exchange chromatographic separation of rare earth elements in geological materials for their determination by inductively coupled plasma atomic emission spectrometry

Abstract

Ion exchange chromatographic separation of the rare earth elements (REEs) in geological materials for their determination by inductively coupled plasma atomic emission spectrometry has been improved. The time taken for the procedure, the consumption of reagents and the external contamination of the samples have been reduced. The emission of corrosive vapours has been totally eliminated. The efficiency of the chromatographic separation by elution with two concentrations of hydrochloric acid has been confirmed at higher flow rates in a high pressure chromatographic column. A prototype has been designed to combine the use of a pressure operated chromatographic column with the simultaneous evaporation of the eluates and the recovery of the acid. The column was charged with the solution resulting from the decomposition of the sample and the matrix elements were eluted with 2 mol l^–1 HCl and the REEs with 6 mol l^–1 HCl. The REE fraction from the column was concentrated by distillation. The whole process (separation and concentration) was performed in 1 h 15 min. The saving in time reached a factor of 30. The recoveries of the REEs during the ion exchange procedure ranged from 96 to 105%. The accuracy and precision have been evaluated by analysing seven geological reference materials: NIM-G (Granite), NIM-L (Lujavrite), NIM-N (Norite), SY-2 (Syenite), SY-3 (Syenite), MRG-1 (Gabbro), and JB-1a (Basalt). Differences between obtained and certified values were not statistically significant for α= 0.05 (t-test). The precision varied from 1.8 to 18.2%.