Development of an analytical method for accurate and precise determination of rare earth element concentrations in geological materials using an MC-ICP-MS and group separation

Abstract

The concentration of rare earth elements (REEs) in geological materials including SLRS-6 (natural water certified reference material) and JB1b, JA1, and JG2 (Standard Rock Materials of Geological Survey of Japan) can be used as a tracer to characterize various geochemical processes in earth systems. Particularly, accurate and precise determination of rare earth element concentration in natural waters is difficult due to their extremely low concentration and the interference of polyatomic oxides. In this study, we developed a method for accurate and precise determination of the REE (particularly heavy rare earth elements) concentrations in geological materials including natural waters using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) and group separation by 2-hydroxyisobutyric acid (HIBA). The REEs were separated into light rare earth elements (LREEs, La–Ce–Pr–Nd), middle rare earth elements (MREEs, Sm–Eu–Gd–Tb), and heavy rare earth elements (HREEs, Dy–Ho–Er–Tm–Yb–Lu) by a cation-exchange column (AG50W-X8 200–400 mesh) using HIBA. The recovery rates of each REE in the natural water sample exceeded 98%, whereas the recovery rates of each REE in rock materials exceeded 95% except for HREEs. The method developed in this study can accurately measure the REE concentrations (particularly HREE) in geological materials without polyatomic oxide interference during the REE analysis by using the MC-ICP-MS and, thus, can correctly interpret the geochemical implications of REEs in geological systems. The determination of the Sr concentrations and Sr isotopic ratios of SLRS-6 CRM and JB1b, JA1, and JG2 SRMs is also reported, and they are shown to be in good agreement with the recommended values.

Advances in Analytical Techniques and Applications in Exploration, Mining, Extraction, and Metallurgical Studies of Rare Earth Elements

“…Stable isotopes have a lot of applications in exploration, water and soil management, and in tracer studies. On the other hand, radiogenic isotope pairs, like 147 Sm- 143 Nd, and 176 Lu- 176 Hf, are used for dating applications to determine the ages of rocks and minerals, and also to evaluate the nature and evolution of their source regions. REE isotopes in geological materials are applied very extensively in geological sciences to obtain new insights into several natural processes, ranging from crustal formation to chemical weathering and ocean circulation.…”

“…Lee and Ko [143] determined REE concentrations in a natural river water CRM, SLRS-6, very accurately and precisely after group separation by 2-hydroxyisobutyric acid (HIBA). As isotope dilution methods are highly accurate and robust, Kent et al [144] used isotope dilution-MC-ICP-MS (ID-MC-ICP-MS) to accurately determine eleven REE abundances in several international geological CRMs (USGS, NIST, GSJ) using rock powders and glass discs made of these rock powders.…”

“…The isotope dilution method is the most accurate method for the determination of metals using mass spectrometry methods. Shen et al [225] determined all REE in BCR-2 (USGS basalt CRM) to be within 2% of expected values (4% for Gd) by isotope dilution MC-ICP-MS without separation of individual elements demonstrating the ability to produce high-quality REE patterns of comparable quality to traditional methods which require labor-and time-intensive REE separation, although some, like Lee and Ko [143], preferred the separation of REEs as a group from the rock matrix for obtaining more accurate data. Adeti et al [27] compared the performances of ICP-MS, INAA, tube-based XRF, and 241 Am excitation-based XRF, for the detection of Sc, La, Ce, Nd, Sm, Eu, Tb, and Lu in volcanic rock specimens from Ghana.…”