Stable Isotope Forensics

Methods and Forensic Applications of Stable Isotope Analysis

Wolfram Meier-Augenstein

• Publisher: Wiley
• Year: 2017
• ISBN:
  9781119080237
• Edition: 2
• Topic: Medicine
• Subtopic: Forensic Medicine

The number-one guide, internationally, to all aspects of forensic isotope analysis, thoroughly updated and revised and featuring many new case studies

This edition of the internationally acclaimed guide to forensic stable isotope analysis uses real-world examples to bridge discussions of the basic science, instrumentation and analytical techniques underlying forensic isotope profiling and its various technical applications. Case studies describe an array of applications, many of which were developed by the author himself. They include cases in which isotope profiling was used in murder, and drugs-related crime investigations, as well as for pharmaceutical and food authenticity control studies.

Updated with coverage of exciting advances occurring in the field since the publication of the 1 st edition, this 2 nd edition explores innovative new techniques and applications in forensic isotope profiling, as well as key findings from original research. More than a simple update, though, this edition has been significantly revised in order to address serious problems that can arise from non-comparable and unfit-for-purpose stable isotope data. To that end, Part II has been virtually rewritten with greater emphasis now being placed on important quality control issues in stable isotope analysis in general and forensic stable isotope analysis in particular.

• Written in a highly accessible style that will appeal to practitioners, researchers and students alike
• Illustrates the many strengths and potential pitfalls of forensic stable isotope analysis
• Uses recent case examples to bridge underlying principles with technical applications
• Presents hands-on applications that let experienced researchers and forensic practitioners match problems with success stories
• Includes new chapters devoted to aspects of quality control and quality assurance, including scale normalisation, the identical treatment principle, hydrogen exchange and accreditation

Stable Isotope Forensics, 2 nd Edition is an important professional resource for forensic scientists, law enforcement officials, public prosecutors, defence attorneys, forensic anthropologists and others for whom isotope profiling has become an indispensable tool of the trade. It is also an excellent introduction to the field for senior undergraduate and graduate forensic science students.

"All students of forensic criminology, and all law enforcement officers responsible for the investigation of serious crime, will want to study this book. Wolfram highlights the value, and future potential, of Stable Isotope Forensics as an emerging powerful tool in the investigation of crime."

—Roy McComb, Deputy Director, Specialist Investigations, National Crime Agency (NCA), UK

" A single author text in these days is rare and the value of this book lies in the dedication and experience of the author which is evident in the clarity of prose, the honest illustration of evidence and the realistic practical application of the subject - it makes this a text of genuine scientific value."

— Prof Dame Sue Black, PhD, DBE, OBE, FRSE, Leverhulme Research Centre for Forensic Science, University of Dundee, UK

The book provides an excellent, vivid and comprehensible introduction into the world of stable isotope science and analytics. Compared to the first edition, the aspects of quality control and assurance in the analysis of stable isotopes in general, and forensic application in particular, are now taking much more room. This allows the book to serve the target groups: students, academic professionals and practitioners, and serves as a solid resource of basic and applicable information about the strengths and potential pitfalls of the application of stable isotope signatures. The present high-quality book shows the great potential of stable isotopes and is a must for everyone interested in isotope forensics.
M.E. Böttcher & U. Flenker, Isotopes in Environmental and Health Studies, January 2018. A list of errata is available at http://booksupport.wiley.com

Part I

How it Works

Chapter I.1

What are Stable Isotopes?

Of the 92 natural chemical elements, almost all occur in more than one isotopic form, with the vast majority being stable isotopes, which do not decay, unlike radioisotopes, which are not stable and hence undergo radioactive decay. To put it another way, 61 of these 92 natural chemical elements appear in two or more stable isotopic forms. So, in this context “almost all” means with the exception of 20 stable chemical elements, including fluorine, sodium and phosphorus, which are mono-isotopic. Making up the difference between 81 and 92 are 11 naturally occurring radioactive chemical elements, including radon and technetium. The word isotope was coined by Professor Frederick Soddy at the University of Glasgow and borrows its origin from the two Greek words isos (ισοζ) meaning “equal in quantity or quality” and topos (τοποζ) meaning “place or position”, with isotope hence meaning “in an equal position” (of the Periodic Table of the Elements). Incidentally, Frederick Soddy was awarded the Nobel Prize in Chemistry in 1921 for his work on the origin and nature of isotopes. By coining this term he referred to the fact that isotopes of a given chemical element occupy the same position in the Periodic Table of the Elements since they share the same number of protons and electrons, but have a different number of neutrons. The word isotope therefore does not denote radioactivity, as is so often mistakenly thought. As mentioned above, radioactive isotopes have their own name, radioisotope. Non-radioactive or stable isotopes of a given chemical element share the same chemical character and only differ in atomic mass (or mass number A), which is the sum of protons and neutrons in the nucleus.

Moving from the smallest entity upwards, atoms are composed of positively charged protons and neutral neutrons, which make up an atom's nucleus, and negatively charged electrons, which make up an atom's shell or electron cloud. Due to charge balance constraints, the number of protons is matched by the number of electrons. A chemical element and its position in the Periodic Table of the Elements is determined by the number of protons in its nucleus. The number of protons determines the number of electrons in the electron cloud and the configuration of this electron cloud in turn determines chemical characteristics such as electronegativity and the number of covalent chemical bonds a given element can form. Owing to this link, the number of protons in the atomic nucleus of a given chemical element is always the same and is denoted by the atomic number Z, while the number of neutrons (in its nucleus) may vary. Since the number of neutrons (N) has no effect on the number of electrons in the electron cloud surrounding an atom the overall chemical properties of an element are not affected. In other words, a chemical element like carbon will always behave like carbon irrespective of whether the number of neutrons in its nucleus is N or N + 1. However, differences in mass-dependent properties can cause compounds containing different amounts of carbon with N or N + 1 neutrons or at different positions to behave subtly differently, both chemically and physically.

Mass number A (= Z + N) and atomic number Z (= number of protons) are denoted as whole numbers in superscript and subscript, respectively, to the left of the element symbol. So carbon-12, comprising six protons and six neutrons is written as

while carbon-13, which comprises six protons and seven neutrons, is written as

. In general practice different isotopes of the same chemical element are denoted by mass number and chemical symbol only, for example ²H or ¹³C.

The simplest of chemical elements, hydrogen (H), in its most abundant isotopic form has a nucleus comprising a single proton and therefore has the atomic weight of 1 (in atomic mass units, amu) and this is indicated by adding a superscript prefix to the element letter, that is, ¹H. The less abundant and 1 neutron heavier hydrogen isotope is therefore denoted as ²H, although one will also find the symbol D being used since this stable hydrogen isotope has been given the name deuterium. The discovery of this isotope won Harold C. Urey the Nobel Prize in Chemistry in 1934, and today Urey is regarded as one, if not the father of modern stable isotope chemistry.

Staying with hydrogen as example, one could say ¹H and its sibling ²H are identical twins that have different weights and different abundances. In the case of hydrogen, the weight difference between the more abundant ¹H and the less abundant ²H is one atomic mass unit. The same is true for the carbon twins. Here sibling carbon-13 (¹³C) is the heavier twin, weighing 1 amu more than its sibling carbon-12 (¹²C), and as is the case for the two hydrogen isotopes the heavier ¹³C is again the less abundant of the two stable carbon isotopes. However, in the case of carbon the actual weight difference of 1 amu amounts to a relative weight difference of only 8.33 % for ¹³C relative to...