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The isotope dilution (ID) method, owing to its high precision, is extensively used for the determination of element mass fractions in a wide range of natural samples. One of the prerequisites of the ID method is knowledge of the isotopic composition of an enriched spike, which is often challenging to accurately determine. In this study, we employ a regression mass bias correction model to accurately and precisely measure the isotopic composition of an enriched Hf spike (Lot No. 159293, Oak Ridge National Laboratory). A NIST SRM 3134 Re solution, whose isotopic composition was calibrated by an NRC IRIS‐1 Ir isotope standard, was used to calibrate the isotopic composition of the Hf spike. The obtained ratios of 176Hf/177Hf, 179Hf/177Hf and 180Hf/177Hf were 0.2406 ± 0.0005 (u, k = 1), 2.8620 ± 0.0005 (u, k = 1) and 384.65 ± 0.05 (u, k = 1), respectively, which meet the required precision levels for Hf isotopes in the application of the ID method. The combined uncertainties of the calibrated Re and Hf isotope ratios were evaluated using a Monte Carlo method, in which the uncertainty of the primary calibrator (IRIS‐1, 193Ir/191Ir = 1.6866 ± 0.0005, u, k = 1) was also taken into consideration. The precision of Hf spike was improved significantly compared with the SSB and C‐SSBIN methods. To the best of our knowledge, this is the first report of isotope ratio calibration in an enriched spike using the regression model. The precisely calibrated spike can lower the uncertainty of the Hf mass fraction significantly, thereby increasing the accuracy of the Lu‐Hf chronometer. [ABSTRACT FROM AUTHOR]

Determination of gold abundances in natural rock is critical for applications, but very challenging. Here, we report a method for determining gold with a very low mass fraction (> 0.01 ng g−1) in rocks. The method involves Carius tube digestion with reverse aqua regia, chromatographic separation to remove most of the sample matrix and measurement by high‐sensitivity ICP‐MS. The mono‐isotopic element gold was quantified by external calibration using an internal standardisation of gold to platinum that was precisely determined by isotope dilution. The method is robust and the obtained results are indistinguishable (< 5–10%, 2s) from those independently obtained by a standard addition technique on the same solution. The results from reference materials TDB‐1 and GPt‐2 are consistent with the certified values and those determined by HF‐aqua regia digestion, confirming the validity of the method. TDB‐1 (n = 20), GPt‐2 (n = 6), BHVO‐2 (n = 9) and other mafic RMs are homogenous for gold (10–20%, 2s) at the 2 g test portion level; however, sample heterogeneity affects some RMs. Gold and platinum‐group elements also display different extents of sample heterogeneity for different RMs. Given the homogeneity observed for TDB‐1, GPt‐2 and BHOV‐2, they are recommended as well‐suited RMs for inter‐laboratory comparison studies of gold. [ABSTRACT FROM AUTHOR]

Bromine and iodine are important tracers for geochemical and environmental studies. In this study, a rapid acid digestion (HNO3 + HF) with ammonia dilution for the simultaneous determination of bromine and iodine in soils and sediments using ICP‐MS was developed. The recoveries of Br and I were controlled by the synergic effect of temperature and time. It took only 15 min at 140 °C for the complete recovery of Br and I in sediment (GSD‐2) and soil (GSS‐24) reference materials, which is a process that needs 2–6 h at 90 °C. A serious loss of Br and I was found at a higher digestion temperature of 190 °C. A 5% v/v NH4OH dilution effectively eliminated the memory effects and stabilised the signals of Br and I. Moreover, ammonia dilution also avoided the corrosiveness of HF on the sample introduction system and torch of ICP‐MS. Tellurium is a more suitable internal standard element than In in the ammonia medium. To avoid the adsorption of residues of dissolution on Te, addition of Te should be carried out after centrifuging the solution. The developed method was successfully applied to determine Br and I in fifty‐three Chinese soil and sediment reference materials. This simple method shows great potential for the rapid determination of Br and I in large batches of geological and environmental samples commonly analysed for mineral exploration and environmental geochemistry studies. [ABSTRACT FROM AUTHOR]

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Copyright of Geostandards & Geoanalytical Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geostandards & Geoanalytical Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)