Geostandards and Geoanalytical Research最新文献

This chapter (The Inductively Coupled Plasma) 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 A Handbook of Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

Chapter 5 (from Section 1 of the handbook dealing with fundamentals of measurement and instrument design) is a comprehensive treatment of the inductively coupled plasma – a significant cornerstone of modern geoanalytical spectrometry. The Chapter includes discussion of plasma formation and key components of the ICP source. This is followed by an examination of the challenges of sample introduction into the plasma, particularly focussed on the introduction of liquid samples. The physical structure of the plasma, its robustness and interference effects are fully examined prior to a section dealing with how the operation of plasma is optimised in practise.

This chapter (Laser-Induced Breakdown Spectroscopy (LIBS)) 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 A Handbook of Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

Chapter 13 (from Section 3 of the handbook dealing with microbeam techniques) provides first a history of the development of laser-induced breakdown spectroscopy, and of the LIBS process, followed by an examination of the fundamental principles of LIBS and its instrumentation. Discussion is then provided on the preparation of sample material, LIBS matrix effects and signal processing. Different modes of compositional analysis that can be tackled by LIBS are described, including quantitative measurement (covering isotope measurements), compositional mapping, depth profiling and the determination of physical properties of geological materials. The recent tandem coupling of LIBS with laser ablation ICP-MS instrumentation is explored. Finally, a suite of examples of LIBS analyses of silicate rocks and minerals is provided, demonstrating the utility of this measurement principle in rapid compositional assessment, detailed petrological studies and microgeochemical mapping.

This chapter (Sampling as Part of the Measurement Process) 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 A Handbook of Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow).

Chapter 1 (Part 2) forms part of Section 1 of the handbook dealing with fundamentals of measurement and instrument design. The geochemical measurement process is considered to begin when the primary sample is taken from the sampling target, rather than when that sample arrives at the laboratory. This integration of sampling within the measurement procedure enables both sampling and chemical analysis to be optimised in order to achieve a measurement procedure that is fit for its intended geochemical purpose. The key metric in judging this fitness for purpose, and hence validating a measurement procedure, is the uncertainty of each measurement value. This measurement uncertainty is explained, together with methods to estimate and express it in a way that includes the contribution from sampling, with a worked example. The resultant more realistic estimates of measurement uncertainty are shown to improve the reliability of the geochemical interpretation of measurement values.

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.

Secondary ion mass spectrometry (SIMS) is often used to determine the sulfur contents and isotope ratios of metallic alloys in meteorites or high-pressure experimental samples. However, SIMS analyses involve calibration and the determination of instrumental mass fractionation in reference materials with a matrix composition similar to that of the unknown samples. To provide metallic reference materials adapted to S measurements via SIMS, we synthesised a series of twenty-eight alloys comprising four FeNi(±Si) compositions (Fe₉₅Ni₅, Fe₉₀Ni₁₀, Fe₈₀Ni₂₀, and Fe₈₀Ni₁₅Si₅) with S contents varying from 100 μg g⁻¹ to 4 g/100g using the “melt spinning” method, which guarantees that the metal alloys are rapidly quenched at ~ 10⁶ K s⁻¹. Sulfur contents were determined at the Service d'Analyse des Roches et Minéraux at the CRPG and absolute δ³⁴S values were determined by multi-collector ICP-MS (MC-ICP-MS, ThermoScientific Neptune) and isotope ratio mass spectrometry (Thermoscientific Delta V). A δ³⁴S value of 16.01 ± 0.31‰ was consistently obtained using the MC-ICP-MS, which was indistinguishable of the δ³⁴S value of the FeS starting material (15.95 ± 0.08‰). It suggests that S did not undergo isotopic fractionation during the melting process. Of fifteen samples containing ≤ 5000 μg g⁻¹ S, SIMS measurements with 15-μm-diameter spots were repeatable to within 10% relative (1 standard deviation, 1s) for S contents and 2‰ for δ³⁴S values. However, samples containing > 5000 μg g⁻¹ S showed FeNi–FeS immiscibility, leading to minor dispersion of the S mass fractions and δ³⁴S values. No matrix effect was observed for Fe-Ni, Si, or S contents in terms of the calibration curves and instrumental mass fractionation. We ultimately recommend eight samples as reliable reference materials for S isotopic measurements by SIMS, which we can share worldwide with other laboratories.