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Library of Congress Cataloging-in-Publication Data
Infrared and Raman spectroscopy in forensic science / [edited by] John M. Chalmers, Howell G. M. Edwards, Michael D. Hargreaves. – 1
p. cm.
Includes bibliographical references and index.
ISBN 978-0-470-74906-7 (hardback)
1. Forensic sciences. 2. Infrared spectroscopy. 3. Raman spectroscopy. 4. Criminal investigation. I. Chalmers, John M. II. Edwards, Howell G. M., 1943- III. Hargreaves, Michael D.
HV8073.I4424 2012
363.25′6–dc23
2011037212
A catalogue record for this book is available from the British Library.
Print ISBN: 978-0470-749067
John Chalmers would like to, yet again, apologise to his wife Shelley for her enduring the role of being a book editor's partner, despite having promised previously not to take such a task on again; maybe this will be the last!
Howell Edwards dedicates this book to his wife Gillian and daughter Katharine who have supported him throughout and to his research supervisor, Dr Leonard Woodward at the University of Oxford, who first stimulated what proved to be his lifelong interest in Raman spectroscopy.
Mike Hargreaves would like to thank his partner Jen, family and his fellow editors for their patience and understanding and for sometimes failing to juggle everything.
John M. Chalmers
Howell G.M. Edwards
Michael D. Hargreaves
July 2011
About the Editors
John M. Chalmers CChem FRSC
John Chalmers “early retired” at the end of 1999 from the United Kingdom chemical company ICI plc; John spent 34 years working with vibrational spectroscopy techniques while employed within research departments of ICI; he retired as a Business Research Associate in the Molecular Spectroscopy Team, Science Support Group, ICI Technology, Wilton Research Centre, UK. In 1994 John was the recipient of the Williams–Wright Award presented by The Coblentz Society for outstanding contributions in the Field of Industrial Infrared Spectroscopy. In 2000, John became a self-employed consultant (VS Consulting) specialising in vibrational spectroscopy; he also took up part-time positions as a Senior Research Fellow and then a Special Lecturer for a period of about 10 years within the School of Chemistry at the University of Nottingham. John has also been a visiting lecturer to the School of Chemical Sciences, University of East Anglia, from 1992–2000. Among his spectroscopic society activities, John is a Past President (2008) of the Society for Applied Spectroscopy (SAS), having served SAS previously as both a Governing Board Member and an International Delegate; John was Chair of the UK Infrared and Raman Discussion Group (IRDG) for nine years (1995–2003).
John has published over 50 peer-reviewed technical papers in scientific journals; he has also had published over 20 book chapters or reference articles. He has co-authored one book (Industrial Analysis with Vibrational Spectroscopy, with Geoffrey Dent, 1997, Royal Society of Chemistry, Cambridge); John has also edited or co-edited several books, including the highly acclaimed reference work the five-volume Handbook of Vibrational Spectroscopy (co-edited with Professor Peter Griffiths, 2002, published by John Wiley & Sons, Ltd, Chichester). Edited or co-edited book titles published include: Spectroscopy in Process Analysis (2000, Sheffield Academic Press, Sheffield), Raman Spectroscopy in Archaeology and Art History (with H.G.M. Edwards, 2005, Royal Society of Chemistry, Cambridge), Molecular Characterization and Analysis of Polymers (with Robert J. Meier, 2008, published by Elsevier, Amsterdam); and the books with titles published by John Wiley & Sons, Ltd., Chichester are: Vibrational Spectroscopy of Polymers: Principles and Practice (with Neil J. Everall and Peter R. Griffiths, 2007), Applications of Vibrational Spectroscopy in Pharmaceutical Research and Development (with Don E. Pivonka and Peter R. Griffiths, 2007), Vibrational Spectroscopy for Medical Diagnosis (with Max Diem and Peter R. Griffiths, 2008), Applications of Vibrational Spectroscopy in Food Science (two-volume set, with Eunice C.Y. Li-Chan and Peter R. Griffiths, 2010). John is also currently the Article Editor for Spectroscopy Europe.
Professor H.G.M. Edwards M.A., B.Sc., D.Phil., C.Chem. FRSC, Emeritus Professor of Molecular Spectroscopy
Howell Edwards studied Chemistry at Jesus College, University of Oxford, and carried out research for his DPhil at Oxford on chemical applications of Raman spectroscopy under the supervision of Dr. Leonard Woodward. Following a Research Fellowship at Jesus College in the University of Cambridge he took a lectureship in Structural and Inorganic Chemistry at the University of Bradford where he became Reader and then Professor of Molecular Spectroscopy and Head of the Chemical and Forensic Sciences Division. In 2003, he received the Sir Harold Thompson Award from Elsevier Science for his international contributions to vibrational spectroscopy. He is the recipient of the Emanuel Boricky Medal for 2008/2009 from Charles University, Prague, for distinguished international contributions to geochemistry and mineralogical analysis. In his research career he has published over 1000 papers on Raman spectroscopy and its applications and is the co-editor of three books: A Handbook of Raman Spectroscopy: From the Research Laboratory to the Process Line (with I.R. Lewis, 2001, Marcel Dekker, New York), Selected Topics in Raman Spectroscopic Applications: Geology, Biomaterials and Art (with F. Rull Perez, P. Vandenabeele and D.C. Smith, 2007, Publidisa Valladolid), and Raman Spectroscopy in Archaeology and Art History (with J.M. Chalmers, 2005, RSC Publishing, Cambridge). He is the recipient of the 2011 Charles Mann Award of the international Federation of Analytical Spectroscopic Societies (FACSS) for distinguished work in applications of Raman spectroscopy. Professor Edwards is a member of the Editorial Boards of J. Raman Spectroscopy, J. Molecular Structure, Spectrochimica Acta, Vibrational Spectroscopy, Drug Targeting and Analysis and Asian J. Spectroscopy. He is Associate Editor of the International Journal of Astrobiology.
Professor Edwards has wide-ranging interests in the applications of Raman spectroscopy to the characterisation of materials in forensic, art historical, polymer, pharmaceutical and archaeological contexts, the characterisation of contraband biomaterials (ivories and drugs of abuse), and spectroscopic molecular signatures relating to the biological survival of cyanobacteria in putative Martian terrestrial analogues. He is international lead coordinator of the Science Team on the RLS Raman instrument with the NASA/European Space Agency on the ExoMars project for the construction and terrestrial evaluation of a miniature Raman spectrometer adopted for a planetary robotic lander for surface and subsurface exploration and search for life on Mars. The Raman spectroscopic characterisation of contraband biomaterials, including the evaluation of portable Raman spectrometers for the field acquisition of data on ivories and drugs of abuse of forensic relevance, has been carried out with support from the Engineering and Physical Sciences Research Council and sponsored by security and law enforcement agencies.
Michael D. Hargreaves MChem, PhD, CSci, CChem, MRSC
Michael Hargreaves studied chemistry at the University of Newcastle upon Tyne, United Kingdom, and carried out a PhD under the supervision of Professor Mike George and Associate Professor Barrie Kellam at the University of Nottingham, UK, on reaction monitoring using FT-IR and Raman spectroscopy.
He undertook two postdoctoral positions with Professor Howell Edwards, at Bradford University, UK, the first on portable Raman spectroscopy for identification/screening of biomaterials, drugs of abuse and explosives, the second on evaluation and development of the RLS Raman detector and geological library with European Space Agency/NASA on the ExoMars project.
After this Mike joined industry, working for Cobalt Light Systems, with Professor Pavel Matousek, commercialising SORS and transmission Raman spectroscopy. He left to join Ahura Scientific in the Application Development Group; Ahura Scientific was subsequently acquired by Thermo Fisher Scientific, where Mike remains within the Portable Analytical Instruments Group.
Michael Hargreaves has authored or co-authored over 30 publications, covering the application of vibrational spectroscopy to the fields of drugs of abuse, explosives, pharmaceutics, geology, biomaterials and works of art.
John M. Chalmers
Howell G.M. Edwards
Michael D. Hargreaves
July 2010
List of Contributors
W. James Armstrong, Forensic Science Northern Ireland, Carrickfergus, UK
Edward G. Bartick, Retired: FBI Laboratory – Counterterrorism and Forensic Science Research Unit, Current: Director of the Forensic Science Program, Department of Chemistry and Biochemistry, Suffolk University, Boston, USA
Steven E.J. Bell, School of Chemistry and Chemical Engineering, Queen's University, Belfast, UK
Victoria L. Brewster, Laboratory for Bioanalytical Spectroscopy, School of Chemistry, Manchester Interdisciplinary Biocentre University of Manchester, Manchester, UK
Christopher D. Brown, Thermo Fisher Scientific Portable Optical Analyzers, Thermo Fisher Scientific, Wilmington, USA
Kevin Buckley, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK; and UCL Institute of Orthopaedics and Musculoskeletal Science, Stanmore Campus, Royal National Orthopaedic Hospital, Stanmore, UK
Lucia Burgio, Science Section, Conservation Department, Victoria and Albert Museum, London, UK
Andrew D. Burnett, School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK
Mary W. Carrabba, Department of Chemistry, Southern Oregon University, 1250 Siskiyou Boulevard, Ashland, USA
John M. Chalmers, VS Consulting, Stokesley, UK
Philippe Colomban, Laboratoire de Dynamique, Interactions et Réactivité – UMR7075, CNRS, Université Pierre-et-Marie-Curie, 4, Place Jussieu, 75005 Paris, France
John E. Cunningham, School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK
A. Giles Davies, School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK
Paul Dean, School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK
A. Deneckere, Ghent University, Department of Analytical Chemistry, Krijgslaan, Ghent, Belgium
Howell G.M. Edwards, Chemical and Forensic Sciences, School of Life Sciences, University of Bradford, Bradford, UK
Marina Epelboym, European Gem Lab- EGL USA, 580 Fifth Avenue, New York, USA
Karen Faulds, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, UK
Peter M. Fredericks, Queensland University of Technology, Brisbane, Australia
Craig Gardner, Thermo Fisher Scientific Portable Optical Analyzers, Thermo Fisher Scientific, Wilmington, USA
Royston Goodacre, Laboratory for Bioanalytical Spectroscopy, School of Chemistry, Manchester Interdisciplinary Biocentre University of Manchester, 131 Princess Street, Manchester, UK
Robert L. Green, Thermo Fisher Scientific Portable Optical Analyzers, Thermo Fisher Scientific, Wilmington, USA
Peter R. Griffiths, University of Idaho, Department of Chemistry, Renfrew Hall, Moscow, USA
A. Guedes, Centro de Geologia e Departamento de Geociências, Ambiente e Ordenamento do Território da Faculdade de Ciências, Universidade do Porto, Porto, Portugal
Michael D. Hargreaves, Thermo Scientific Portable Optical Analyzers, Thermo Fisher Scientific, Wilmington, USA
Wayne Jalenak, Thermo Fisher Scientific Portable Optical Analyzers, Thermo Fisher Scientific, Wilmington, USA
Jan Jehlika, Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Prague, Czech Republic
Kathryn S. Kalasinsky, Armed Forces Institute of Pathology, Washington D.C., USA
Lore Kiefert, Guebelin Gem Laboratory, Maihofstrasse, Luzern, Switzerland
Kaho Kwok, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, USA
Ian R. Lewis, Kaiser Optical Systems, Inc., Ann Arbor, USA
Mary L. Lewis, I. R. Lewis, Kaiser Optical Systems, Inc., Ann Arbor, USA
Edmund H. Linfield, School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK
Juan Manuel Madariaga, Department of Analytical Chemistry, University of the Basque Country, Bilbao, Spain
Pavel Matousek, Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, UK
L. Moens, Ghent University, Department of Analytical Chemistry, Ghent, Belgium
Ute Münchberg, Institute of Physical Chemistry, Friedrich-Schiller-University Jena, Helmholtzweg Jena, Germany
Hpone-Phyo Kan-Nyunt, GIA Laboratory Bangkok, U-Chu-Liang Building, Bangkok, Thailand
Andrew J. O'Neil, School of Pharmacy and Chemistry, Kingston University, Kingston Upon Thames, UK
Vincent Otieno-Alego, Forensic and Data Centres, Australian Federal Police, Australia
Banu Özen, Department of Food Engineering, zmir Institute of Technology, Urla, zmir, Turkey
Susan Paralusz, Consulting Gemologist, North Brunswick, New Jersey, USA
Jürgen Popp, Institute of Physical Chemistry, Friedrich-Schiller-University Jena, Helmholtzweg Jena, Germany; and Institute of Photonic Technology e. V. (IPHT), Jena, Germany
A.C. Prieto, Departamento de Física de la Materia Condensada, Cristalografía y Mineralogía, Universidad de Valladolid, Spain
A. Reip, Wolfson Centre for Materials Processing, Brunel University, Kingston Lane, Uxbridge, UK
Paola Ricciardi, National Gallery of Art, 2000B South Club Drive, Landover, USA
Petra Rösch, Institute of Physical Chemistry, Friedrich-Schiller-University Jena, Jena, Germany
J. Silver, Wolfson Centre for Materials Processing, Brunel University, Kingston Lane, Uxbridge, UK
W. Ewen Smith, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow, UK; and Renishaw Diagnostics Ltd, Nova Technology Park, Glasgow, UK
Naomi Speers, Forensic and Data Centres, Australian Federal Police, Australia
S. James Speers, Forensic Science Northern Ireland, Carrickfergus, UK
Samantha P. Stewart, School of Chemistry and Chemical Engineering, Queen's University, Belfast, UK
Stephan Stöckel, Institute of Physical Chemistry, Friedrich-Schiller-University Jena, Jena, Germany
Lynne S. Taylor, Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, USA
Figen Tokatli, Department of Food Engineering, zmir Institute of Technology, Urla, zmir, Turkey
P. Vandenabeele, Ghent University, Department of Archaeology, Ghent, Belgium
R. Withnall, Wolfson Centre for Materials Processing, Brunel University, Kingston Lane, Uxbridge, UK
Mark R. Witkowski, FDA Forensic Chemistry Center, Trace Examination Section, USA
Preface
For many years the practices of infrared and Raman spectroscopy were confined largely to dedicated academic, industrial or national research laboratories. Major technical advances over the past 10–20 years have afforded a significant broadening of the applicability of these vibrational spectroscopy techniques as a whole.
Instruments used to be large, complicated to operate, with even the simplest experiment often challenging to set up and run. Advances in technology have resulted in smaller, easier to use instrumentation that is much more user-friendly. Demands and needs from users for increased portability of scientific instrumentation have produced spectrometers and interferometers of small dimensions and of sufficient quality such that handheld Raman and Fourier transform infrared (FT-IR) instruments have been realized over the past few years, opening up much wider application of Raman and FT-IR spectroscopy to forensic science applications, particularly for adoption into field usage.
This book is intended to introduce a novice or established spectroscopic practitioner of analytical chemistry to the technical elements of Raman and infrared spectroscopy as applied to forensic science, outlining several proven and potential applications within this field. It is not intended to describe advanced topics such as non-linear Raman or time-resolved vibrational spectroscopy, but rather to address the applications of Raman and IR spectroscopy to the different fields of forensic work, from explosives to narcotics and from bio-agents to works of art.
The early chapters introduce the reader to the principles of forensic science and how Raman and IR spectroscopy can be applied. Chapter 2 introduces the basics of vibrational spectroscopy and the instrumentation that may be found routinely, ranging from bench-top through portable to handheld systems. To complement this, Chapter 3 discusses sampling techniques and considerations of analysis to aid in the non-destructive analysis of samples.
The following sections of the book are split into overviews and case-study chapters comprising topics covering the following areas: crime scene, counter terrorism/homeland security, drugs of abuse, archaeology/mineralogy and consumer products, including pharmaceutics. Each chapter is written by internationally respected scientists. This broad selection of topics is complemented by relevant application examples, highlighting how IR, Raman and terahertz (THz) spectroscopy can be applied to these fields. To complement this, each chapter is referenced so that users can read up on and investigate areas that interest them.
Commercial Raman, near-IR, mid-IR and THz spectrometers differ widely in their applicability, configuration and performance. No one system can be applied to all possible applications; specific manufacturers are mentioned within the text to identify a particular approach, configuration or application. Where manufacturers are mentioned, this does not infer an endorsement, but it may be useful to the reader to understand the special design or application objectives and requirements.
It is the editors' and contributors' hope that those just developing an interest in the application of infrared and Raman spectroscopy to forensic analysis and that those who practice it already will find this book useful not only as a source of new information, but also as a reference work. Furthermore, we hope that it will inspire readers to delve deeper into the applications of vibrational spectroscopy that have not yet been explored in this rapidly expanding field.
Notes on convention (or lack of them): it is usual practice to plot IR spectra from high wavenumber (on the left) to low wavenumber (on the right); this convention is held throughout the book. Raman shifts are often shown plotted either way, that is, low shift (on the left) to high shift (on the right) or vice versa. It has not been possible to ensure all the spectral plots have been standardised in this way, particularly those that have been reproduced from other publications, so readers are directed to check the individual plots. In addition, the Raman shift axis only shows the Stokes-shifted bands, unless stated otherwise. Mostly Raman shifts are noted in the unit cm−1, rather than the more correct form of Δ cm−1.
John M. Chalmers
Howell G.M. Edwards
Michael D. Hargreaves
August 2011
Chapter 1
Introduction and Scope
John M. Chalmers1, Howell G.M. Edwards2 and Michael D. Hargreaves3
1VS Consulting, Stokesley, UK
2Chemical and Forensic Science, University of Bradford, Bradford, UK
3Thermo Scientific Portable Optical Analyzers, Thermo Fisher Scientific, Wilmington, Mass., USA
1.1 Historical Prologue
Forensic science can be defined as the application of scientific principles to the public domain in courts of law, which were held by the Romans in the public forum.
Although evidence of the unlawful killing of a human being was presented in public fora from quite early times, such as the post mortem examination of the body of Julius Caesar after his assassination, which revealed 23 stab wounds but only one of which was judged to be fatal, and poisoning in particular, where the appearance of organ degradation gave rise to the conclusions that toxic materials had been ingested, these pronouncements were in the realm of the prototype medical examiners and pathologists and not chemical analysts [1].
The first chemical analysis of an historical artefact that can be viewed as “forensic” in its approach was reported in the literature by Sir Humphry Davy in 1815. The development of the Marsh test for arsenic poisoning in 1836 was a landmark event that launched the birth of analytical forensic science. This was followed quite rapidly by the public fascination for scientific analysis applied to crime as appeared in the Victorian gothic novel in detective stories such as Armadale [2], authored by Wilkie Collins in 1866, and culminating in the adventures of Sherlock Holmes, whose creator Sir Arthur Conan Doyle introduced in A Study in Scarlet [3] in December 1887, just one year before the notorious “Jack the Ripper” brought terror to the East End of London, England. Subsequently, some 56 of Conan Doyle's short stories, published in the popular Strand Magazine between 1891 and 1927, commencing with A Scandal in Bohemia, established the Sherlock Holmes genre to an appreciative public; an unsuccessful attempt by Conan Doyle to terminate the Holmes character in a fatal meeting with his arch-enemy Professor Moriarty at the Reichenbach Falls in 1893 resulted in intense public outrage; such was the growing public perception of the scientific approach to crime solution at that time, and the detective re-appeared to his public once more in The Hound of the Baskervilles in 1901.
The seemingly voracious appetite of readers for the scientific detection of crime in the mid-nineteenth century is illustrated in Armadale by the attempt by Miss Gwilt to murder her fiancé, the eponymous Armadale of the novel, using a chemical reaction between an unspecified liquid in a purple flask supplied by a mysterious admirer and the generation of an odourless, tasteless and undetectable gas whilst he was sleeping. The author had acknowledged appropriately the assistance and advice of an un-named professional chemist in the preface to his novel, thereby lending a veneer of respectability and credibility to the background science contained in the text! The activities of Sherlock Holmes and his analytical skills and observations pervade the Conan Doyle stories and hint at the prophetic accomplishments of Conan Doyle, said to be based upon his University mentor, Dr Joseph Bell, that were significantly in excess of the extant knowledge in the late 1880s.
It is, therefore, perhaps not surprising that the first recorded acceptance of forensic chemical analysis used in a court of law to secure a conviction occurred as late as 1912 in France when Emile Gourbin, who had a seemingly good, watertight alibi, was faced with evidence of his poisoning of his lover, Marie Latelle, using contaminated poudre de riz, a customised cosmetic preparation that was fashionable at that time. The scientific analyst at the centre of this landmark prosecution was Edmond Locard, who demonstrated that particles of material under the fingernails of the accused matched the composition of the cosmetic preparation purchased from a local pharmacist but with the addition of bismuth. It is interesting that some years later in 1927, this same Edmond Locard, then a professor at the University of Lyon, proposed his now famous and fundamental eponymous Exchange Principle that is at the basis of modern forensic science: that “every vigorous contact leaves a trace”.
There quickly followed the establishment of analytical laboratories internationally dedicated to forensic science, early examples of which in France was that of Edmond Locard in 1910 and in the United States by August Vollmer in 1924. The first Chair of Legal Medicine in a University, so establishing an academic forensic protocol, was established in Harvard in 1932.
A classic case of murder by poisoning that first escaped detection in the United Kingdom but which relied heavily upon chemical analysis to secure prosecution, was that of Major Herbert Armstrong, who systematically poisoned his wife using arsenic in 1921; only when he tried to repeat the exercise to remove a business rival did Major Armstrong receive his just desserts – a close relative of the business rival was the local pharmacist, who recollected that Armstrong had purchased large quantities of arsenic over the previous year. Exhumation of the Major's wife revealed to the pathologist a large amount of arsenic in her remains – as exemplified by the adoption of the Marsh test; Armstrong was convicted of her murder and hanged in 1922 [4, 5].
The use of infrared spectroscopy to determine molecular structure has its roots firmly established in the nineteenth century, since the discovery of the infrared region of the electromagnetic spectrum in 1800 by Sir William Herschel. But the Raman effect was first observed experimentally only in 1928 by Sir Chandrasekhar Raman, following a theoretical prediction by Smekal in 1923, which resulted in the Nobel Prize for Physics for Raman in 1930. Lord Rayleigh, commenting on the observation of the Raman effect, judged this to be one of the four most important discoveries in physics of all time.
At first, the relative ease of recording photographically the wavenumber-shifted radiation of the weak Raman effect compared favourably with the point by point plotting of moving coil galvanometer signals used in infrared spectroscopy and gave an impetus to Raman spectroscopy in molecular structure analysis that surpassed the infrared investigations. However, it became quickly apparent that the onset of fluorescence emission swamped the weaker Raman data, often saturating the photographic emulsions used in the spectrographic recording. For many years this disadvantage was paramount in Raman spectroscopy and it was only the advent of tuneable laser excitation and novel methods of detection coupled with computerised data acquisition that offered possibilities to circumvent it. Hence, although mid-infrared spectroscopy started to be applied to forensic analysis from the 1950s, Raman spectroscopy was only similarly used from the 1990s; in both cases, however, the coupling of a microscope to the analytical spectrometer was a necessary advancement. The advent of portable and handheld spectrometers has further advanced this application space, meaning analysts can analyse in situ artefacts of interest.
In the past, the greatest stumbling block to the application of both infrared spectroscopy and Raman spectroscopy to forensic structural analysis and molecular characterisation was the quantity of material that was required for analysis and the further requirement that in most cases the preparation of the specimen for the optical illumination processes necessitated the destruction, mechanically or chemically, of the sample itself. This was paralleled in chemical analysis, in that even as early as 1815 Davy [6] recognised that his experiments on the archaeological decorative wall painting artefacts from the recently excavated Pompeii archaeological site resulted in the complete destruction of the samples presented for analysis. Even 100 years later, Eccles and Rackham [7], in their comprehensive studies of porcelains in the British Museum and Victoria and Albert (V&A) Museum collections in the United Kingdom required the donation of multiple items from tea and dinner services which were sacrificed in the determination of factory body chemical compositions using wet chemical analysis. It was, therefore, a very important turning point in the mid-twentieth century when it was realised that advances in spectroscopic technology now made available for the first time the possibility of acquiring chemical molecular data from valuable specimens that was truly non-destructive of the sample [8–10].
In the 1970s great strides forward were made when optical microscopes were coupled with spectroscopes to provide chemical identification data from spatially minimal regions of samples. The first infrared microspectrometer appeared in the mid-1960s and the first Raman microspectrometer was announced from the laboratory of Michel Delhaye and Paul Dhamelincourt in the University of Lille, France, in 1976; this was termed a molecular optical laser examiner (MOLE) which was quickly applied to the investigation of several interdisciplinary problems, including some fragments from oil paintings. The first papers in this area, which could perhaps be classified as ground-breakers for the later application of Raman microscopy in forensic science, then appeared from the laboratories of the Natural History Museum of Paris under the direction of Bernard Guineau, who analysed the inorganic pigments from mediaeval manuscripts in museum collections [11].
1.2 The Application of Infrared Spectroscopy and Raman Spectroscopy in Forensic Science
Both techniques share a microspectroscopic capability for the recording of data from particles in the nanogram to picogram range, which is paramount for the interrogation of specimens non-destructively; little if any sample preparation is required, which means that vibrational spectroscopy is often regarded as a first-pass analytical technique for the screening and identification of suspect materials which then may require some further analytical data from more destructive operations.
Naturally, infrared spectroscopy and Raman spectroscopy have particular advantages and disadvantages, which sometimes dictate that one or other technique is preferred for special applications: for example, the presence of water or hydrated chemical species in specimens can hamper the mid-infrared analysis and the ready inaccessibility with mid-infrared spectrometers of low wavenumber features below 400 cm–1 can severely limit the characterisation of drug polymorphs and heavy metal inorganics. The operational dependence of the Raman effect upon molecular polarisability rather than the dipole moment for the infrared means that polar groups such as –OH and C=O are better seen in the infrared spectrum, whereas homopolar unsaturation involving C=C groups and N=N is better evidenced in the Raman spectrum. The degradation of keratotic materials such as skin, hair and nail associated with human remains in burial environments is best followed through the –S–S– modes near 500 cm–1 in the Raman spectrum as this feature does not appear at all in the infrared spectrum.
A major factor in Raman spectroscopy applications to materials in a forensic context is the ability to overcome or circumvent fluorescence emission and this needed the advent of laser excitation at longer wavelengths from the visible into the near-infrared region of the electromagnetic spectrum, typically at 785, 830 or 1064 nm. Modern state of the art vibrational spectroscopic laboratories involved in forensic analysis therefore have several laser sources available for adoption in this respect, especially where samples are highly coloured, such as pigments and dyes.
Field–use capability of instrumentation is a desirable development for the adoption of miniaturised infrared and Raman spectrometers at crime scenes and for the examination of large or very fragile objects and artefacts. In this context, the penetration of packaging and the interrogation of specimens through transparent or semitransparent containers is also possible through shrewd selection of the radiation wavelength, and the possibilities of the terahertz (THz) region of the spectrum is affording much interest in this respect. An important factor here is the incorporation of database recognition packages within the chosen instrument to identify materials that are of relevance to forensic examination, such as drugs of abuse, explosives, chemical warfare agents and their chemical precursors, which may be correlated with drugs factories and synthetic bomb-making crime scenes. The use of such instrumentation by non-expert security forces and agents by the adoption of selection algorithms is also a real challenge for specialised spectroscopists.
Of special interest is the recording of seized specimens of suspect materials that can be examined whilst still contained in their evidential bags sealed at source and which need not be sampled or opened in the analytical laboratory; the data from such analyses carried out under these conditions can circumvent any doubts raised about the integrity of the preservation of the evidential material between the source and the analytical laboratory This type of analysis has a distinct parallel in the scientific examination of artworks, which for operational reasons cannot be removed from their transparent covers or holders; in a “forensic art” study [12] of the Armada Jewel made for Queen Elizabeth I by Nicholas Hilliard, a prestigious court limner, in 1588, and now in the V&A Museum in London, the Raman spectroscopic characterisation of the pigments used was achieved by interrogation of the painting through its rock crystal cover plate, with some rather surprising results.
Finally, the so-called molecular fingerprint that is provided from the mid-infrared spectrum or Raman spectrum must be well-characterised and robust: for example, the question arises as to how many vibrational spectroscopic features are necessary to define a particular compound unequivocally – this is not easy to assess and sometimes it is relatively easy to differentiate between chemically similar materials and not so in other cases. In pigment characterisation, for example, the two forms of lead (II) oxide are readily differentiated in the low wavenumber region using Raman spectroscopy; in the geological field, anatase can readily be differentiated form rutile and brookite, yet all are titanium (IV) oxides; and the polymorphs of calcium carbonate, calcite and aragonite are easily discriminated by both mid-infrared and Raman spectroscopy. In each case, the detection of more than one vibrational spectroscopic feature is essential for correct identification of the specimen. In the area of drugs analysis, cocaine hydrochloride and freebase cocaine (crack cocaine) can be differentiated as can caffeine base and caffeine hydrate. The power of these techniques thus rests in an appreciation of the necessity for recording spectra of the best quality consistent with speed and rapid identification that is often a de rigueur requirement of the end user.
This book comprises overview chapters and case study chapters written by experts and practitioners who have a wealth of experience in the application of infrared, Raman and THz vibrational spectroscopic techniques to forensic analysis in which several of the points made above are investigated and exemplified; several outstanding challenges remain that need the collaboration of vibrational spectroscopists, forensic practitioners and front-line security forces in the advancement of technologies in the fight against crime, contraband trafficking and international terrorism.
References
1. W.J. Tilstone (2006) Forensic Science: An Encyclopedia of History, Methods and Techniques, ABC-CLIO, Santa Barbara, Calif.
2. Armadale (1866) Wilkie Collins, Smith, Elder, London.
3. A Study in Scarlet, in Beeton's Christmas Annual (1887) November issue, Ward Lock, London.
4. J.W. Nicholson (1992) Arsenic – the enigmatic element, Education in Chemistry, July, pp. 101–103.
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