Complete Trace Elemental Characterisation of Granitoid (USGS G‐2, GSP‐2) Reference Materials by High Resolution Inductively Coupled Plasma‐Mass Spectrometry

Abstract

The United States Geological Survey granitic and granodioritic reference materials G‐2 and GSP‐2 were decomposed in high‐pressure bombs using both HF‐HNO3 and HF‐HNO3‐HClO4 in order to evaluate the feasibility of characterising the entire suite of geologically relevant trace elements through direct analysis with a high‐resolution inductively coupled plasma‐mass spectrometer (HR‐ICP‐MS). The digested samples were diluted to the appropriate levels and analysed at low, medium and high resolution depending on the required sensitivity and potential interferences for each element. Memory effects during analysis of the high field strength elements (HFSE) were negligible when analysed using an all‐Teflon, uncooled sample introduction system and combined with adequate wash times with 4% v/v aqua regia + 0.5% v/v HF between samples. The concentration of the remaining lithophile elements was determined with a conventional, cooled, Scott‐type spray chamber using a wash solution of 1% v/v HNO3. Total procedural blanks contributed between 0.01 to 0.5% to final sample concentrations and blank subtractions were typically unnecessary. Abundances for Li, Hf, Ba, Zr, Ga, Rb, Sr, La, Ce, Th and U were systematically higher, while those for the heavy rare earth elements (HREEs), Cu and Y were systematically lower in this study compared to USGS values for G‐2 and GSP‐2. This is likely to be related to, respectively, higher recoveries from more efficient digestion of refractory phases (i.e., zircon, tourmaline), and better resolution of interferences when using a HR‐ICP‐MS. Sample digestion experiments also showed that perchloric acid digestion in high pressure bombs resulted in superior recoveries and better precision for the bulk of the trace elements analysed. The concentration of the remaining elements overlapped within uncertainty with recommended reference values and with values determined in other studies using isotope‐dilution TIMS, ICP‐MS and XRF. Concentrations for the elements Cd, Sn, Sb, Ta, Bi, Tb, Ni and Mo are also reported for G‐2 and GSP‐2 reference materials. Our study shows therefore that it is feasible to determine thirty‐nine geologically relevant trace elements accurately and directly in granitoid sample digests when using a HR‐ICP‐MS, thereby negating the need for ion exchange or isotopic spiking.

Simple and cost-effective methods for precise analysis of trace element abundances in geological materials with ICP-MS

“…Alkali fusion technique is effective to decompose resistant accessory minerals, but it causes high blank levels (i.e., flux impurities) and total dissolved solids (TDS). 5 Besides, its high Si content can also cause complex isobaric interferences [3], plus causing significant instrumental drift during analysis due to silicate salt deposits in the interiors of the sample/skimmer cones [9]. In this case, the high-pressure digestion (bomb) method remains the method of choice, especially when applied to coarse grained granitic and metamorphic rocks [10][11][12].…”

“…Also, the analytical precision and accuracy also depend on instrument conditions and methods employed [5]. While the ICP-MS technique has been significantly matured over the past ~ 30 years, various isobaric interferences as the result of sample introduction and transport to the ICP remain one of the problems to be monitored and overcome [6].…”

Assimilation of preexisting Pleistocene intrusions at Long Valley by periodic magma recharge accelerates rhyolite generation: rethinking the remelting model

“…Any fluorides formed upon drying were redissolved with a mixture of HClO 4 (*150 ll) and 4 N HNO 3 (*500 ll) at 120°C on a hot plate over night. Whole rock dissolutions at the PCIGR were performed as in Pretorius et al (2006). Chromatographic purification of Hf from zircon and whole rocks was performed using procedures employed at the PCIGR originally developed by Goolaerts et al (2004).…”

Occurrence of red clay horizon in soil profiles of the Yellow River Delta: Implications for accumulation of heavy metals

“…Briefly, 4.0 g of each soil sample was weighed and backing with 2.0 g boric acid in the mold, then pressed it into a 32-mm diameter pellet at 30 t pressure for 10 s. The prepared powder pellets were directly measured on XRF. Cd was determined by ICP-MS (ELAN DRC II, Perkin Elmer) after highpressure Teflon bomb digestion with strong acids such as HF (5 mL), HNO 3 (2 mL) and HClO 4 (1 mL) at 180°C for 12 h (Pretorius et al, 2006). Quality assurance and quality control were assessed using duplicates and standard reference materials (GSS-1, GSS-4, GSS-6, GSS-8) from National Research Center for Certified Reference Materials of China with 10% of the samples.…”