Application of an argon-nitrogen inductively-coupled radiofrequency plasma (ICP) to the analysis of geological and related materials for their rare earth contents

• Published in: Spectrochimica acta. Part B: Atomic spectroscopy 1981, Vol.36 (8), p.785-797
• Main Authors: Brenner, I.B., Watson, A.E., Steele, T.W., Jones, E.A., Goncalves, M.
• Format: Article
• Language: English
• ISSN: 0584-8547; 1873-3565
• DOI: 10.1016/0584-8547(81)80061-4

An account is given of the development of a procedure for the determination of the rare earth (RE) elements in a large variety of geological materials employing a medium power argon-nitrogen ICP coupled with a 3.4m Ebert spectrograph. The effects of the carrier and intermediate gas flow rates, height of observation and power on RE spectral line intensities have been studied. The line-to-background ratio of the RE analyte was found to increase with observation height and passed through a maximum at 12–14 mm above the top of the work coil. The method eventually developed allows the direct determination of the lanthanides and yttrium at the 50–200 μg g −1 levels using a single solution prepared by fusing 0.2–1 g samples with Na 2O 2 or LiBO 2 and dissolving the melt in 4–10% (v/v) HNO 3, or by treating the samples with HF-HClO 4-HNO 3 mixtures. For lower contents of the RE elements, they can be separated from matrix concomitants by ion exchange employing AG50W-X8 resin. A large variety of silicate and phosphate reference materials was analysed using scandium as the internal standard. The relative standard deviations vary from about 1.5–15%. No matrix effects were observed despite the large compositional variation of the samples analysed.