Isotopic Analysis E-Book
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- Herausgeber: Wiley-VCH
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Edited by two very well-known and respected scientists in the field, this excellent practical guide is the first to cover the fundamentals and a wide range of applications, as well as showing readers how to efficiently use this increasingly important technique.
From the contents:
* The Isotopic Composition of the Elements
* Single-Collector ICP-MS
* Multi-Collector ICP-MS
* Advances in Laser Ablation - Multi-Collector ICP-MS
* Correction for Instrumental Mass Discrimination in Isotope Ratio Determination with Multi-Collector ICP-MS
* Reference Materials in Isotopic Analysis
* Quality Control in Isotope Ratio Applications
* Determination of Trace Elements and Elemental Species Using Isotope Dilution ICP-MS
* Geochronological Dating
* Application of Multi-Collector ICP-MS to Isotopic Analysis in Cosmochemistry
* Establishing the Basis for Using Stable Isotope Ratios of Metals as Paleoredox Proxies
* Isotopes as Tracers of Elements Across the Geosphere-Biosphere Interface
* Archaeometric Applications
* Forensics Applications
* Nuclear Applications
* The Use of Stable Isotope Techniques for Studying Mineral and Trace Element Metabolism in Humans
* Isotopic Analysis via Multi-Collector ICP-MS in Elemental Speciation
A must-have for newcomers as well as established scientists seeking an overview of isotopic analysis via ICP-MS.
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Veröffentlichungsjahr: 2012
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Contents
Preface
List of Contributors
Chapter 1: The Isotopic Composition of the Elements
1.1 Atomic Structure
1.2 Isotopes
1.3 Relation Between Atomic Structure and Natural Abundance of Elements and Isotopes
1.4 Natural Isotopic Composition of the Elements
References
Chapter 2: Single-Collector Inductively Coupled Plasma Mass Spectrometry
2.1 Mass Spectrometry
2.2 The Inductively Coupled Plasma Ion Source
2.3 Basic Operating Principles of Mass Spectrometers
2.4 Quadrupole-Based ICP-MS
2.5 Sample Introduction Strategies in ICP-MS
2.6 Spectral Interferences
2.7 Measuring Isotope Ratios with Single-Collector ICP-MS
References
Chapter 3: Multi-Collector Inductively Coupled Plasma Mass Spectrometry
3.1 Introduction
3.2 Early Multi-Collector Mass Spectrometers
3.3 Variable Multi-Collector Mass Spectrometers
3.4 Mass Resolution and Resolving Power
3.5 Three-Isotope Plots for Measurement Validation
3.6 Detector Technologies for Multi-Collection
3.7 Conclusion
References
Chapter 4: Advances in Laser Ablation–Multi-Collector Inductively Coupled Plasma Mass Spectrometry
4.1 Precision of Isotope Ratio Measurements
4.2 Stable Signal Intensity Profiles: Why So Important?
4.3 Signal Smoothing Device
4.4 Multiple Ion Counting
4.5 Isotope Fractionation During Laser Ablation and Ionization
4.6 Standardization of the Isotope Ratio Data
Acknowledgments
References
Chapter 5: Correction of Instrumental Mass Discrimination for Isotope Ratio Determination with Multi-Collector Inductively Coupled Plasma Mass Spectrometry
5.1 Historical Introduction
5.2 Mass Bias in MC-ICP-MS
5.3 Systematics of Mass Bias Correction Models
5.4 Logic of Conventional Correction Models
5.5 Pitfalls with Some Correction Models
5.6 Integrity of the Correction Models
5.7 The Regression Model
5.8 Calibration with Double Spikes
5.9 Calibration with Internal Correction
5.10 Uncertainty Evaluation
5.11 Conclusion
References
Chapter 6: Reference Materials in Isotopic Analysis
6.1 Introduction
6.2 Terminology
6.1 Determination of Isotope Amount Ratios
6.4 Isotopic Reference Materials
6.5 Present Status, Related Problems, and Solutions
6.6 Conclusion and Outlook
References
Chapter 7: Quality Control in Isotope Ratio Applications
7.1 Introduction
7.2 Terminology and Definitions
7.3 Measurement Uncertainty
7.4 Conclusion
References
Chapter 8: Determination of Trace Elements and Elemental Species Using Isotope Dilution Inductively Coupled Plasma Mass Spectrometry
8.1 Introduction
8.2 Fundamentals
8.3 Selected Examples of Trace Element Determination via ICP-IDMS
References
Chapter 9: Geochronological Dating
9.1 Geochronology: Principles
9.2 Practicalities
9.3 Various Isotopic Systems
9.4 Systems for Which ICP-MS Analysis Brings Fewer Advantages
Acknowledgments
References
Chapter 10: Application of Multiple-Collector Inductively Coupled Plasma Mass Spectrometry to Isotopic Analysis in Cosmochemistry
10.1 Introduction
10.2 Extraterrestrial Samples
10.3 Origin of Cosmochemical Isotopic Variations
10.5 Use of MC-ICP-MS in Cosmochemistry
10.5 Applications of MC-ICP-MS in Cosmochemistry
10.6 Conclusion
Acknowledgments
References
Chapter 11: Establishing the Basis for Using Stable Isotope Ratios of Metals as Paleoredox Proxies
11.1 Introduction
11.2 Isotope Ratios of Metals as Paleoredox Proxies
11.3 Diagenesis: a Critical Area for Further Work
References
Chapter 12: Isotopes as Tracers of Elements Across the Geosphere–Biosphere Interface
12.1 Description of the Geosphere–Biosphere Interface
12.2 Elements That Typify the Geosphere–Biosphere Interface
12.3 Microbes at the Interface
12.4 Element Tracing in Environmental Science and Exploration of Metal Deposits
12.5 Isotopes as Indicators of Paleoenvironments
12.6 Tracing the Geosphere Effect on Vegetation and Animals
12.7 Tracing in the Marine Environment
12.8 Future Directions
References
Chapter 13: Archeometric Applications
13.1 Introduction
13.2 Current Applications
13.3 New Applications
13.4 Conclusion
References
Chapter 14: Forensic Applications
14.1 Introduction
14.2 Forensic Applications Based on ICP-MS Isotopic Analysis
14.3 Future Outlook
Acknowledgments
References
Chapter 15: Nuclear Applications
15.1 Introduction
15.2 Rationale
15.3 Process Control and Monitoring in the Nuclear Industry
15.4 Isotopic Studies of the Distribution of U and Pu in the Environment
15.5 Nuclear Forensics
15.6 Prospects for Future Developments
Acknowledgment
References
Chapter 16: The Use of Stable Isotope Techniques for Studying Mineral and Trace Element Metabolism in Humans
16.1 Essential Elements
16.2 Stable Isotopic Labels Versus Radiotracers
16.3 Quantification of Stable Isotopic Tracers
16.4 Isotope Labeling Techniques
16.5 Concepts of Using Tracers in Studies of Element Metabolism in Humans
16.6 ICP-MS in Stable Isotope-Based Metabolic Studies
16.7 Element-by-Element Review
Acknowledgments
References
Chapter 17: Isotopic Analysis via Multi-Collector Inductively Coupled Plasma Mass Spectrometry in Elemental Speciation
17.1 Introduction
17.2 Advantage of On-Line versus Off-Line Separation of Elemental Species
17.3 Coupling Chromatography with MC-ICP-MS
17.4 Environmental and Other Applications
17.5 Conclusion and Future Trends
References
Index
Related Titles
The Editors
Prof. Dr. Frank Vanhaecke
Ghent University
Dept. of Analytical Chemistry
Krijgslaan 281 - S12
9000 Ghent
Belgium
Prof. Dr. Patrick Degryse
Katholieke Universiteit Leuven
Center for Archaeol. Sciences
Celestijnenlaan 200 E
3001 Leuven
Belgium
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Preface
Although several instrumental techniques allow information on the isotopic composition of target elements to be obtained, mass spectrometry is without doubt the most versatile and most powerful.
For isotopic analysis of metals and metalloids, thermal ionization mass spectrometry (TIMS) has been the “gold standard” for a long time. Although also serving other purposes, such as accurate and precise determination of element concentrations in the context of the production of reference materials and characterization of materials from the nuclear industry, TIMS was predominantly deployed in the domain of geo- and cosmochemistry. The introduction of single-collector inductively coupled plasma mass spectrometry (ICP-MS) in 1983 and, especially, of multi-collector (MC) ICP-MS about a decade later, however, had a tremendous impact on the field of “isotopic analysis.” The much higher ionization efficiency of the inductively coupled plasma (ICP) ion source, the enhanced sample throughput, and the flexibility in terms of sample introduction are the reasons most quoted to explain the current success of MC-ICP-MS. In effect, MC-ICP-MS is gradually replacing/has gradually replaced TIMS as the “gold standard” for isotopic analysis by now.
ICP-MS was not immediately introduced as a tool for isotopic analysis, but as a very powerful technique for (ultra-)trace element determination, combining the multi-element capabilities of inductively coupled plasma optical emission spectrometry (ICP-OES) with an even higher detection power than atomic absorption spectrometry (AAS). As a result, the user community of ICP-MS was different from that of TIMS, although also here the geochemical community has often been working at the forefront of development, especially in the domains of isotopic analysis and of direct bulk and spatially resolved analysis by using laser ablation (LA) as a means of sample introduction. However, by using ICP-MS instead of spectrometric techniques such as AAS or ICP-OES that have only marginal capabilities for isotopic analysis, also scientists from other fields learned to appreciate the additional capabilities offered by the isotope-specific information that a mass spectrometric technique provides. In fact, all ICP-MS users rely on isotopic information, for example, for identifying element patterns in the mass spectrum and for revealing and correcting for spectral interferences via mathematical equations. A new community of users discovered the merits of isotope dilution as a calibration approach, not only as a means for obtaining the highest accuracy and precision, but also for compensating for analyte losses during sample pretreatment and element speciation procedures, and more “adventurous” uses of isotope dilution were explored. Given the diversity of the ICP-MS community, it came as no surprise that the technique was also increasingly used for tracer experiments with stable isotopes aiming at obtaining a more profound insight into various physical processes and (bio)chemical reactions in the context of both fundamental physicochemical studies, for example, concerning reaction rates, and applied research, for example, in environmental and biomedical studies. The user community also started to use ICP-MS for determining isotope ratios that show variation in Nature as a result of the presence of one (e.g., Sr) or more (e.g., Pb) radiogenic isotopes although, as a result of the rather modest precision of single-collector ICP-MS, only the less demanding cases could be tackled in this way.
The gap in isotope ratio precision existing between TIMS and single-collector ICP-MS was bridged by the introduction of MC-ICP-MS, in which the noisy character of the ICP ion source is counteracted by simultaneous monitoring of the ion beams involved, a practice that was already established earlier in TIMS. The user community of MC-ICP-MS nowadays seems to consist of two groups: researchers from the geo- and cosmochemical domain have added MC-ICP-MS to their instrumentation and/or replaced (part of their) TIMS instruments by MC-ICP-MS devices, while single-collector ICP-MS users looking for an improved isotope ratio precision are also keen MC-ICP-MS users.
The introduction of MC-ICP-MS has not only facilitated the work otherwise done using TIMS, it also allows the study of elements that were previously not or barely accessible using TIMS. The most prominent example is Hg, the volatility of which precludes the use of TIMS. Furthermore, the introduction of MC-ICP-MS has revolutionized the field as its use contributed strongly to the current awareness that the isotopic composition not only shows variations as a result of isotope fractionation for the lighter elements, but actually varies for all of them, even for U, the heaviest naturally occurring element.
As the community of MC-ICP-MS users is more diverse than that of TIMS was/is for the reasons outlined above, there seemed to be a demand for a book on isotopic analysis via single- and multi-collector ICP-MS with a wider scope, one that addresses not only applications from the domains of geo- and cosmochemistry (but certainly also without denying the pioneering role that researchers in this research field have played and are still playing), but also from other areas, such as archeometry, forensics, and biomedical studies. The Editors were invited to realize such a book, a task that could only be completed with contributions from prominent scientists from diverse fields. It was the intention to provide a book that is accessible to the interested newcomer to the field, while also supplying the more experienced user with some new insights. To achieve this goal, both the very basics and also advanced topics are addressed, as detailed below.
Chapter 1 especially aims at providing newcomers to the field with general information on the origin of natural variations in the isotopic composition of metals and metalloids.
Chapters 2 and 3 present an overview of single- and multi-collector ICP-MS instrumentation and their respective capabilities. Also appropriate ways to overcome spectral overlap are addressed. As the ICP is a robust ion source operated at atmospheric pressure, there are various means of sample introduction. Although pneumatic nebulization of sample solution is the standard approach, LA of solid material avoids the need for digestion in bulk analysis, and also allows spatially resolved information to be obtained. Recent advances in LA are discussed in Chapter 4, in which the fundamental technical challenges associated with the handling of transient signals are also considered.
Although MC-ICP-MS permits isotope ratios to be measured with very high precision (down to 0.002% RSD), it needs to be realized that the raw data show a substantially larger bias (1% per mass unit order of magnitude at mid-mass) with respect to the corresponding true value. This bias is caused by preferential transmission of the heavier isotope during the extraction process, and obviously this instrumental mass discrimination needs to be corrected for. The methods used for this purpose are discussed into detail in Chapter 5.
Chapters 6 and 7 focus on the “quality” of isotope ratio measurement data by concentrating on isotopic reference materials (and the current shortage thereof) and on the total uncertainty accompanying all measurement data.
Chapter 8 provides the reader with the basic principles of isotope dilution mass spectrometry used for elemental analysis and also discusses more advanced features of this calibration approach, such as its use in direct solid sample analysis and in elemental speciation work, wherein not the total amount but that of various chemical species of a target element need to be determined.
Chapter 9 presents an accessible overview of methods for geochronological dating and illustrates the capabilities and limitations of MC-ICP-MS in this context with real-life applications reported in the literature.
Chapters 10–12 put geo- and cosmochemical applications in the spotlight. Chapter 10 clarifies the origin of cosmochemical isotopic variations and explains how these variations can be exploited for advancing insight into the universe and our solar system with its planetary bodies. Chapters 11 and 12 bring the reader back to Earth. Chapter 11 addresses paleoproxies in more detail, but instead of providing an overview of all the contexts in which it is attempted to reconstruct paleoconditions (e.g., pH, temperature, redox potential, salinity) prevailing during a physicochemical process in the past by investigating an isotopic signature systematically affected by the above-mentioned conditions, this chapter focuses on paleoredox proxies only and discusses into detail all factors that jeopardize a correct interpretation in this context. Chapter 12 then provides a more general description of how isotopes can be used as tracers of elements across the geosphere–biosphere interface.
Chapters 13 and 14 illustrate how the isotopic composition of selected target elements may be interpreted as a fingerprint, providing information on the provenance of materials and objects of relevance in an archeometric or forensic context.
In Chapter 15, nuclear applications are described and it is clarified in which contexts ICP-MS is superior to radiometric techniques that have to rely on the actual decay of the radionuclides present in the sample for data collection.
Isotopic analysis using ICP-MS can also advance our insight into the human metabolism, as illustrated extensively in Chapter 16. Various concepts in tracer studies with stable isotopes are delineated and case studies are reviewed on an element-by-element basis. Also, emerging applications based on natural variations in the isotopic composition of mineral elements are considered.
Finally, in Chapter 17, the relatively recent use of MC-ICP-MS in elemental speciation work – realized by coupling a chromatographic separation technique to an MC-ICP-MS device as an isotope-specific detector – is discussed. Also, the consequences of the transient nature of the signals thus obtained on the data collection are considered.
Considerable work both from the Editors and from the other contributors went into the making of this volume. We hope that these efforts have resulted in a book that is considered “useful” by our colleagues working in or interested in working in the still rapidly evolving and fascinating field of isotopic analysis using single- and multi-collector ICP-MS.
Ghent and Leuven, March 2012
Frank Vanhaecke
Patrick Degryse
List of Contributors
David Amouroux
Rasmus Andreasen
Sylvain Berail
Patrick Degryse
Olivier F.X. Donard
Charles Douthitt
Marlina A. Elburg
Vladimir N. Epov
Klaus G. Heumann
Takafumi Hirata
Michael E. Ketterer
Kurt Kyser
Juris Meija
Thomas Meisel
Zoltán Mester
Christophe Pécheyran
Wolfgang Pritzkow
Mark Rehkämper
Martín Resano
Maria Schönbächler
Johannes Schwieters
Ralph E. Sturgeon
Scott C. Szechenyi
Frank Vanhaecke
Jochen Vogl
Thomas Walczyk
Laura E. Wasylenki
Michael Wieser
Lu Yang
Chapter 1
The Isotopic Composition of the Elements
Frank Vanhaecke Kurt Kyser
1.1 Atomic Structure
Early in the twentieth century, Rutherford realized that Thomson’s late nineteenth century plain cake model for the atom, describing the atom as consisting of electrons floating around in a positive sphere, had to be replaced by a “Saturnian” model, describing the atom as consisting of a small central nucleus surrounded by electrons, rotating on rings [1]. This view was supported by a study of the behavior of a beam of α particles (see below, particles resembling the nucleus of an He atom, thus consisting of two protons and two neutrons) directed on to a very thin Au metal foil, known as the Geiger–Marsden experiment [2]. Since only a minor fraction of the α-particles were recoiled or deflected, and for the majority the path was not affected, it had to be concluded that for the largest part, an atom consists of empty space. According to Bohr’s later model [3], the atom contains a nucleus composed of positively charged protons and neutral neutrons, having approximately the same mass. This nucleus is a factor of ∼104 smaller than the size of the atom (although the concept of size itself is not self-evident in this context) and holds practically all of its mass. As they both reside in the nucleus, protons and neutrons are also referred to by the common term nucleon. The negatively charged electrons are substantially lighter (almost 2000 times) and rotate around the central nucleus in different orbits (also termed shells), corresponding to different energy levels. Subsequently, insight into the atomic structure has evolved tremendously and a multitude of other particles have been discovered, but for many chemical considerations – including a discussion of isotopes – the Bohr model still largely suffices.
As all protons carry the positive unit charge (1.602 × 10ࢤ19 C), they mutually repel one another. This electrostatic repulsion is overcome by the so-called nuclear force [4]. This is a very strong force, but effective only within a very short range. In fact, the very short range over which this force is effective even causes the largest nuclei (e.g., those of U) to be unstable (see below). Further clarification of the nature of this nuclear force requires a more thorough discussion of the atomic structure, including a discussion on quarks, but this is beyond the scope of this chapter. Electrostatic attraction between the positive nucleus and the orbiting negative electrons provides the centripetal force required to keep the electrons from drifting away from the nucleus.
1.2 Isotopes
The chemical behavior of an atom is governed by its valence electrons (electron cloud) and, therefore, atoms that differ from one another only in their number of neutrons in the nucleus display the same chemical behavior (although this statement will be refined later). Such atoms are called isotopes and are denoted by the same chemical symbol. The term isotopes refers to the fact that different nuclides occupy the same position in the periodic table of the elements and was introduced by Todd and Soddy in the early twentieth century [5].
To distinguish between the isotopes of an element, the mass number A – corresponding to the sum of the number of protons and the number of neutrons (the number of nucleons) in the nucleus – is noted as a superscript preceding the element symbol: AX. The atomic number Z, corresponding to the number of protons in the nucleus, may be added as a subscript preceding the element symbol but is often omitted as this information is already inherent in the element symbol.
As a result of their difference in mass, isotopes of an element can be separated from one another using mass spectrometry (MS), provided that they are converted into ions. In fact, this is exactly how isotopes were discovered: Thomson separated the ion beams of two Ne isotopes using a magnetic field, while their detection was accomplished with a photographic plate [6]. With a similar setup, typically referred to as a mass spectrograph, Aston was subsequently able to demonstrate the existence of isotopes for a suite of elements [7].
Although several techniques provide a different response for the isotopes of an element, for example, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and neutron activation analysis (NAA), MS is the technique of choice for the majority of isotope ratio applications. The isotopic composition of the light elements H, C, N, O, and S is typically studied via gas source MS, and for C dating, accelerator mass spectrometry (AMS) is replacing radiometric techniques to an increasing extent. For isotopic analysis of metals and metalloids, thermal ionization mass spectrometry (TIMS) and inductively coupled plasma mass spectrometry (ICP-MS) are the methods of choice. This book is devoted to the use of (single-collector and multi-collector) ICP-MS in this context and its basic operating principles, capabilities, and limitations are discussed in Chapters 2 and 3.
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