Determination of Rare Earth Elements and Thorium at Nanogram Levels in Ultramafic Samples by Inductively Coupled Plasma‐Mass Spectrometry Combined with Chemical Separation and Pre‐concentration

Abstract

A method was developed for the determination of low-level rare earth elements (REEs) and thorium in ultramafic samples by inductively coupled plasmamass spectrometry. The conventional method for the digestion of ultramafic rocks using HNO 3 and HF results in considerable amounts of insoluble fluorides because of the high contents of Mg (generally up to 24% m ⁄ m) in these rocks. In this study, we used H 3 BO 3 as a complexing agent to break down the insoluble fluorides, and then separated the REEs from Fe and Mg major and Ba, Ca, Cr minor matrices by anion exchange and coprecipitation, respectively. The whole procedural blanks estimated from sample-free analyses ranged from 0.232 ng for Ce to 0.006 ng for Tm and Lu. Limits of detection for this method, defined as three times the standard deviation of these blank analyses, varied from 0.51 ng g -1 for Ce to 0.03 ng g -1 for Lu. The recovery of REEs using this technique, as determined using the standard addition method, ranged from 92.9% for Y to 102.0% for Er with 3% (RSD) variation. The method was validated using GAS (GeoPT-12), JP-1 and PCC-1, and the results were comparable to literature values, elucidating the applicability to the determination of ultra trace REEs in ultramafic rocks.Keywords: rare earth elements, thorium, ICP-MS, ultramafic rocks, chemical pre-concentration.

Comprehensive Pb‐Sr‐Nd‐Hf isotopic, trace element, and mineralogical characterization of mafic to ultramafic rock reference materials

“…Quality control is particularly important during the analysis of mafic to ultramafic plutonic rocks. Due to the combination of their low to very low levels of trace elements, coarse grain textures, potential presence of refractory accessory minerals (e.g., chromite, zircon), and high contents of MgO, FeO, CaO, or Al 2 O 3 , these materials are more susceptible to both matrix effects [ Barling and Weis , ] and to sample heterogeneity that may make them difficult to completely dissolve by conventional acid digestion techniques [e.g., Yokoyama et al ., ; Tanaka et al ., ; Nakamura and Chang , ; Ulrich et al ., , Sun et al ., ; Chu et al ., ].…”

Determination of Trace Element Mass Fractions in Ultramafic Rocks by HR‐ICP‐MS: A Combined Approach Using a Direct Digestion/Dilution Method and Preconcentration by Coprecipitation

“…In comparison, the direct method gave a slightly lower intermediate precision on HREE (10 < RSD < 15% for MGL-GAS (GeoPT12) and DTS-2B), and the precision is notably worse for MREE (Sm, Eu and Gd) Bayon et al (2009) Direct method (this study) Coprecipitation (this study) Godard et al (2008) Govindaraju ( the coprecipitation method (bold) ( Table 3). Results are compared with literature values from Govindaraju (1995) together with the SARM certificate for UB-N, Raczek et al (2001), Carignan et al (2001), Potts et al (2003), Qi et al (2005, Makishima and Nakamura (2006), Nakamura and Chang (2007), Godard et al (2008), Barrat et al (2008), Bayon et al (2009), Chauvel et al (2011, Gao and Casey (2012), Ulrich et al (2012), Zeng et al (2012), Sun et al (2013) and from the USGS certificate for DTS-2B. 35%.…”

Precise Determination of Sm and Nd Concentrations and Nd Isotopic Compositions in Highly Depleted Ultramafic Reference Materials

“…, Sun et al . ), and making highly precise measurement of Nd isotopes more challenging. Additionally, the fluoride gels that are formed often clog the cation‐exchange columns used for the separation of rare earth elements from the sample matrix; (3) some accessory minerals such as chromite found in some ultramafic rocks are difficult to completely digest using HF + HNO 3 + HClO 4 (Jain et al .…”