Alkali fusion co-precipitation/cation exchange/extraction enrichment for determination of trace rare earth elements in rocks by inductively coupled plasma mass spectrometry

Abstract

In this paper, three separation and pre-enrichment methods of Mg(OH)2 and Fe(OH)3 co-precipitation, cation exchange and 1-phenyl-3-methyl-4-benzoyl-pyrazolone (PMBP) extraction were established by sodium peroxide alkali fusion digestion. Ca, Na and K, etc. were virtually eliminated from the analysis solutions using three sample processing procedures, thereby avoiding potential matrix interference and mass spectrometry interference due to high salt content. The detection limits of three methods were 0.0009-0.0076 mg/kg，0.0011-0.0062 mg/kg，0.0023-0.0114 mg/kg, respectively；the relative deviations of the determined rare earth elements (REEs) were -6.9-7.6%, -9.1-6.6% and -8.4-12.3%，respectively. The %RSD values of the three methods were lower than 10%, demonstrating good precision. The fit for purpose of the results was also evaluated by the quality criteria test proposed by the International Geological Correlation Programme (IGCP), from which it can be deduced that the three methods were adequate considering geochemical mapping application. The three sample processing procedures can be applied for the determination of rare earth elements in rocks.