Abundances of twenty four trace elements, including Y and fourteen rare earth elements (REE), are reported for eighty six geological reference materials and four proficiency testing samples Analytical data were obtained by ICP-MS using solution nebulisation after mixed acid digestion (HF-HClO4) under pressure Analysed samples cover a wide range of element concentrations and mineralogical compositions, including samples for which there are few previously published data Precision for elemental determinations in nearly 90% of the samples analysed is better than 5% Accuracy, estimated by comparison with data from compilations is better than 6% for well characterized reference materials Results obtained for samples that are low in trace elements are often significantly lower than compiled reference values A critical discussion of the compiled data sets, especially for Y and the REEs, indicates that some reference values seem to be erroneous

Reference Materials for Geochemical Studies: New Analytical Data by ICP‐MS and Critical Discussion of Reference Values

Evaluation of the coprecipitation of incompatible trace elements with fluoride during silicate rock dissolution by acid digestion

Complete dissolution is essential to obtain accurate analytical results using ICP-MS. In this study, decomposition techniques (i.e. acid digestions using Savillex Teflon vials, a high pressure digestion system and microwave oven, a combined lithium tetraborate fusion - HF/HNO3 acid decomposition and sodium peroxide sinter) for the total dissolution of different types of geological reference materials have been investigated. Savillex Teflon vial HF/HNO3 digestion is effective for basaltic samples. The high pressure HF/HClO4 digestion (PicoTrace TC-805 digestion system, Bovenden, Germany) allows dissolution of basalts and ironstones. Granites and magnetite-rich samples can be dissolved using a high pressure HF/H2SO4 method. Geological samples cannot be effectively attacked by microwave acid digestion. A combined lithium tetraborate fusion - HF/HNO3 acid digestion method allows complete dissolution of many different types of geological materials; however, this method precludes the determination of volatile elements due to the high fusion temperature (1000 °C). A sodium peroxide sinter method at 480 °C has the potential for the rapid determination of Y, Sc and REE in different types of geological materials. However, the lack of ultra-pure reagents precludes the use of lithium tetraborate fusion and sodium peroxide sinter methods for the measurement of geological samples with low trace element abundances.



La dissolution complete est essentielle pour obtenir des resultats analytiques justes par ICP-MS. Dans cette etude, les techniques de decomposition (i.e., attaques acides utilisant des fioles Savillex en teflon, un systeme d'attaque a haute pression et un four a micro-ondes, une fusion au tetraborate de lithium combinee avec une decomposition acide HF/HNO3 et un frittage avec peroxyde de sodium) pour la dissolution totale de differents types de materiaux geologiques de reference ont eteetudiees. L'attaque HF/HNO3 en flacon teflon Savillex est efficace pour les echantillons de basalte. L'attaque HF/HClO4a haute pression (systeme d'attaque PicoTrace TC-805, Bovenden, Allemagne) permet la dissolution des basaltes et des roches riches en fer. Les granites et les echantillons riches en magnetite peuvent etre dissous par la methode HF/H2SO4a haute pression. Les echantillons geologiques ne peuvent pas etre efficacement attaques par une attaque acide en four a micro ondes. Une methode combinee fusion avec tetraborate de lithium et attaque acide HF/HNO3 permet la dissolution complete de nombreux differents types de materiaux geologiques sauf la determination des elements volatils due a une haute temperature de fusion (1000 °C). Le frittage avec peroxyde de sodium a 480 °C permet la determination rapide de Y, Sc et des Terres Rares dans differents types de materiaux geologiques. Toutefois, L'absence de reactifs ultra-purs exclut L'utilisation de la fusion avec tetraborate de lithium et du frittage avec peroxyde de sodium pour L'analyse de faibles teneurs d'elements en traces dans des echantillons geologiques.

An Evaluation of Methods for the Chemical Decomposition of Geological Materials for Trace Element Determination using ICP-MS

Data are reported for rare earth elements (REE) in three geological glass reference materials (BIR-1G, BHVO-2G and BCR-2G) using a UV (266 nm) laser ablation ICP-MS system and the classical (HF-HClO4) acid decomposition method, followed by conventional nebulisation ICP-MS. External calibration of laser ablation analyses was performed using NIST SRM reference materials with internal standardisation using 29Si and 44Ca. Replicate analyses of reference basaltic glasses yielded an analytical precision of 1-5% (RSD) for all the elements by solution ICP-MS and 1-8% (RSD) by laser ablation ICP-MS. The relative differences between the REE concentrations measured by solution and laser ablation ICP-MS compared with the reference values were generally less than 11 % for most elements. The largest deviations occurred for La determined by solution ICP-MS in BIR-1G. The results of both solution and laser ablation ICP-MS agreed well, generally better than 7%, with the exception of La, Pr and Sm in BIR-1G. The measured REE laser ablation data for BIR-1G, BHVO-2G and BCR-2G agreed with the previously published data on these basaltic reference glasses, within a range of 0-10% for most elements. No significant influences were observed for the predicted spectral interferences on some REE isotopes in the analysis of basaltic glasses.

G.J. Beukes

Papers

Fluoride precipitates in silicate wet-chemistry: implications on REE fractionation