Geostandards and Geoanalytical Research最新文献

This chapter (Principles and Practice of X-Ray Fluorescence Spectrometry – 1: Fundamentals of XRF and Matrix Corrections) is a contribution to the Geostandards and Geoanalytical Research Handbook of Rock and Mineral Analysis – an online textbook that is a fully revised and updated edition of the Handbook of Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

Chapter 6, Part 1 (from Section 2 of the handbook dealing with techniques for the determination of major and trace elements) considers the fundamentals of XRF spectrometry and matrix corrections in detail. Part 2 deals with wavelength dispersive and energy dispersive instrumentation. Following an introduction dealing with the analytical characteristics of XRF spectrometry, Part 1 continues with a detailed consideration of the origin and excitation of X-ray spectra. Sub-chapters that tackle the interaction of X-rays with matter and the matrix effect in geological materials follow this. Part 1 is concluded with a mathematical treatment of the correction of absorption-enhancement effects.

This chapter (Geoanalytical Metrology) is a contribution to the Geostandards and Geoanalytical Research Handbook of Rock and Mineral Analysis – an online textbook that is a fully revised and updated edition of Handbook of Silicate Rock Analysis, which was written by Philip J. Potts and published in 1987 by Blackie and Son (Glasgow). This second edition comprises chapters, written by prominent research scientists, designed to provide comprehensive overviews of the relevant techniques for the elemental characterisation of rocks and minerals. Chapters are designed to allow new practitioners to the field (including research students) to attain a comprehensive understanding of the theory, practice and capabilities of each technique, as well as being of benefit to established research geoanalysts. In addition to the content, chapter titles have been revised where appropriate to reflect progress in this field.

Chapter 1, Part 1 (from Section 1 of the handbook dealing with fundamentals of measurement and instrument design) first sets out the overarching conventions that operate in analytical chemistry, including a description of the international organisations and systems that regulate the standards governing the discipline. This is followed by coverage of the statistical basis on which geoanalytical data sets are treated, analysed and interpreted, which summarises most of the relevant tests and terminology employed in this field. The methods by which the calibration of measured signals from instrumental techniques is tackled, followed by method validation, which covers aspects including measurement uncertainty, bias, precision and trueness. Sections detailing metrological traceability and quality management conclude this chapter.

This chapter (Quadrupole Inductively Coupled Plasma-Mass Spectrometry) is a contribution to the Geostandards and Geoanalytical Research Handbook of Rock and Mineral Analysis – an online textbook that is a fully revised and updated edition of Handbook of the Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

Chapter 7 (from Section 2 of the handbook dealing with techniques for the determination of major and trace elements) describes both the history of ICP-MS, including development of the plasma sampling interface and the operation of modern ICP-MS instrumentation. Given their central importance to ICP-MS operation, ion extraction through the sampling interface, ion transmission, ion separation (with a particular focus on the quadrupole mass filter) and counting are given particular attention. Discussion of the analytical characteristics of ICP-MS particularly focusses on spectroscopic interferences (and their mitigation). Finally, an overview of geochemical analysis by ICP-MS considers drift correction, calibration strategies, and laser ablation microsampling.

In situ ⁸⁷Sr/⁸⁶Sr microanalysis in bioapatite using laser ablation (LA-)MC-ICP-MS is an essential tool for provenance studies, as enamel tissue build-up records the regional Sr isotopic composition of ingested food and water sources. Several factors hamper the acquisition of reliable and precise ⁸⁷Sr/⁸⁶Sr data: isobaric interferences, elemental and isotopic fractionation of Rb and Sr, and the lack of certified reference materials. Here we thoroughly characterise several teeth from Carcharinus leucas (Bull shark) for the spatial distribution of Sr and Rb mass fraction by LA-ICP-Q-MS, and their ⁸⁷Sr/⁸⁶Sr ratio by solution MC-ICP-MS, MC-TIMS and LA-MC-ICP-MS, and which were used subsequently as a reference material during laser ablation measurement of Sr isotope ratios in bioapatite. We establish a protocol to estimate the ⁸⁵Rb/⁸⁷Rb mass bias from the analysis of shark teeth that demonstrates that the common assumption of equal Sr and Rb instrument induced fractionation can lead to a systematic bias in ⁸⁷Sr/⁸⁶Sr isotope ratios. Using the shark teeth as an "external" reference material to measure β_Rb yielded ⁸⁷Sr/⁸⁶Sr compositions in unknown samples that are within approximately -42 ppm to +66 ppm of expected values, instead of approximately -50 ppm to +190 ppm if assuming β_Rb = β_Sr. Finally, this methodology was tested on fossil gomphotherid (Rhynchotherium sp.) enamel, allowing us to make preliminary inferences about its palaeobiogeography.

We present a new set of reference materials, the ND70-series, for in situ measurement of volatile elements (H₂O, CO₂, S, Cl, F) in silicate glass of basaltic composition. The materials were synthesised in piston cylinders at pressures of 1 to 1.5 GPa under volatile-undersaturated conditions. They span mass fractions from 0 to 6% m/m H₂O, from 0 to 1.6% m/m CO₂ and from 0 to 1% m/m S, Cl and F. The materials were characterised by elastic recoil detection analysis for H₂O, by nuclear reaction analysis for CO₂, by elemental analyser for CO₂, by Fourier transform infrared spectroscopy for H₂O and CO₂, by secondary ion mass spectrometry for H₂O, CO₂, S, Cl and F, and by electron probe microanalysis for CO₂, S, Cl and major elements. Comparison between expected and measured volatile amounts across techniques and institutions is excellent. It was found however that SIMS measurements of CO₂ mass fractions using either Cs⁺ or O⁻ primary beams are strongly affected by the glass H₂O content. Reference materials have been made available to users at ion probe facilities in the US, Europe and Japan. Remaining reference materials are preserved at the Smithsonian National Museum of Natural History where they are freely available on loan to any researcher.

In this study, we present a high precision and high spatial resolution in situ Fe isotope protocol using femtosecond (fs) laser ablation multi-collector inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS). The intermediate measurement precision obtained over a period of ca. 3 years for the USGS glass BIR-1G against the Puratronic reference material is 0.17‰ (2s) for δ⁵⁶Fe. Uncertainties achieved on individual analyses of glass and olivines were < 0.15‰ for δ⁵⁶Fe. This high precision is associated with high spatial resolution of about 170 × 25 μm. Our results display good consistency between LA-MC-ICP-MS and solution nebulisation MC-ICP-MS data from the literature. Obtained δ⁵⁶Fe values on different USGS glasses (BIR-1G, BHVO-2G and BCR-2G) show that these reference materials have homogenous Fe isotope ratio and therefore can be used as bracketing calibrators during laser ablation measurement sessions. On the other hand, the San Carlos Olivine displays high Fe isotope heterogeneity, and therefore cannot be considered as a good bracketing standard (calibrator). We also applied our fs-LA-MC-ICP-MS protocol to olivines and pyroxene from the Kerguelen Archipelago. This technique appears to be a relevant tool to resolve isotopic zoning in chemically zoned silicate phenocrysts, even of small size (< 1 mm). We demonstrate that within single lavas, olivine crystals display various zoning depending on their size, related to their residence time in the magma. Both equilibrium and diffusive processes were observed in olivine crystals from Kerguelen, uncovering complex histories. Hence, iron isotope ratio measurements by fs-LA-MC-ICP-MS open new possibilities for studying highly zoned silicate minerals in magmatic rocks to better understand their formation.

Isotope geochemistry requires isotope ratios measured using secondary ion mass spectrometry (SIMS) to be made with optimal precision and accuracy. Under some analytical conditions when using electron multiplier detectors, secondary ions may be under-counted because of quasi-simultaneous arrival (QSA) at the first dynode. The relative magnitude of the associated QSA correction to raw measured isotopic ratios can be up to seventy permil or more. Therefore, not applying the correction, or misapplication of it could lead to significant inaccuracies in published isotope ratio data. Examples and ramifications of the latter are described in addition to a straightforward procedure for QSA under-counting correction.

A simple method was developed for the determination of REEs, Zr, Hf, Th and U in ultramafic rocks by inductively coupled plasma-mass spectrometry with a combination of RE and UTEVA extraction resins for their separation and pre-concentration. Ultramafic rocks were digested with HNO₃-HF-HClO₄ and finally turned into 11 mol l⁻¹ HCl solutions together with H₃BO₃ to remove insoluble fluorides. The removal of matrix elements was achieved during the loading procedure. Following this, REEs on RE resin, and Zr, Hf, Th and U on UTEVA resin were eluted with 10 ml of 0.24 mol l⁻¹ HCl, with recoveries better than 94.4%. This method was validated using reference materials JP-1, DTS-2B, OKUM, UB-N, MUH-1 and DZΣ-2, and the measurement results for target analytes were comparable to literature values, indicating its applicability to the determination of REEs, Zr, Hf, Th and U at ultra-trace level in ultramafic rocks.

A series of three CGSP-P phosphate matrix reference materials, with variable element mass fractions, were synthesised by co-precipitation with CaCl₂ and (NH₄)₃PO₄ to form a hydroxylapatite matrix. Each powder sample was packaged into multiple bottles and pressed into tablets as replicates. The within-bottle homogeneity was evaluated by the repeatability of element mass fractions of six spots in per tablet of CGSP-Ps by LA-ICP-MS. For the between-bottle homogeneity evaluation, one approach adopted the % RSD of element mass fractions in twelve different tablets from twelve bottles in the same reference material in comparison with the repeatability field of LA-ICP-MS analyses obtained from homogeneous glasses, and the other used a one-way analysis of variance (ANOVA) approach. Most of the elements (e.g., Mg, Ca, P, Mn and REE) were homogenous within 10% RSD, and other elements (e.g., Si, Al, K, Rb, Cs and Ni) were considered heterogeneous (with > 20% RSD). All of the elements passed the t-test except Ni in CGSP-P3, and V, Cr, Ni, Zr, Gd, Dy and Th in CGSP-P4 after a 29-month period stability examination by LA-ICP-MS. The preliminary reference values and standard uncertainties for CGSP-Ps are given with a network of methods and eight laboratories by bulk analysis according to ISO Guide 35:2006 and JJF 1343-2012.