Portable Raman Spectroscopy Systems for Field Analysis

By Eckenrode, Brian A.; Bartick, Edward G. et al. | Forensic Science Communications, October 2001 | Go to article overview

Portable Raman Spectroscopy Systems for Field Analysis


Eckenrode, Brian A., Bartick, Edward G., Harvey, Scott D., Vucelick, Mark E., Wright, Bob W., Huff, Rebecca A., Forensic Science Communications


Introduction

A major challenge confronting hazardous materials response teams involves the accurate and rapid identification of organic or inorganic chemicals outside the typical laboratory environment and under potentially dangerous conditions. Extreme care is required when analyzing unknown chemicals because of the possible instability of samples. Many chemicals can be sensitive to shock, heat, or light and could react violently including deflagration and/or explosion. In many cases, determining the nature of the unknown materials, whether biological (microorganisms) or chemical, is important and will dictate the handling, cleanup, disposal, and resolution of civilian issues. Addressing the need for rapid and accurate analysis of samples that are suspected to be dangerous has been difficult for most current commercial analytical instruments available to field agents, especially given the fact that analysis may prove lethal if handled incorrectly.

Raman spectroscopy is a rapid, nonintrusive, and nondestructive technique (in most cases) that can be used for the analysis of many classes of hazardous and potentially explosive compounds. With developments in fiber optics (Carrabba and Rauh 1992), filters (McCreery 1996), diode lasers (Imasaka and Ishibashi 1990), electromagnetic wave detectors (Sweedler et al. 1988), and data analysis software, Raman spectroscopy (Mulvaney and Keating 2000) has been able to move from the laboratory environment to the field (Smith 2000). Raman spectroscopy provides the ability to analyze bulk materials such as milligram (or kilogram) quantities of drugs present in bags or vials, as well as liquids consisting of solvent mixtures present in a variety of containers (Chase 1994). Raman spectroscopy is sensitive to slight differences in chemical structure and has been used to detect contaminants present within a medicinal tablet or gel cap. Raman spectroscopy can also easily and rapidly distinguish between the nitramine high explosives RDX (cyclo-1,3,5-trimethlyene-2,4,6-trinitramine) and HMX (cyclotetramethylene tetranitramine). Both laboratory and field-based Raman systems can provide reliable data with a minimal amount of sample preparation or manipulation and, as such, can be a powerful screening tool for the field analyst. New field-portable, Raman-based instrumentation will find important applicability in helping to ensure the safety of field responders in the FBI Laboratory's Hazardous Materials Response Unit.

The first part of this article is intended to introduce the reader to Raman spectroscopy with particular emphasis on the hardware developments that have allowed this technique to be used more effectively in the field. This initial discussion is also intended to present the hardware and software issues that should be considered when evaluating the latest commercial-portable Raman systems. The latter part of this article addresses strengths and limitations that current commercial-portable Raman instruments have for field use by nonspectroscopists.

Raman Technique

The Raman spectroscopic technique involves directing a monochromatic light source (such as a laser) onto a sample and detecting the scattered light (Ferraro and Nakamoto 1994; Pelletier and Davis 1996). Most of the light is scattered elastically (Rayleigh scatter), but a small fraction is scattered inelastically (Raman scatter). Elastic scatter involves simultaneous emission of photons of the same energy as the incident photons. Rayleigh scattering is very intense relative to Raman scattering and corresponds to the frequency of the incident electromagnetic radiation ([v.sub.ex]). In contrast, Raman scatter is very weak and involves interaction of the incident electromagnetic radiation with the vibrational frequency of the molecule ([v.sub.m]) to produce a shift from the frequency of the excitation wavelength ([v.sub.ex] [+ or -] [v.sub.m]). Specifically, Raman bands are generated by an induced oscillating dipole that is caused by interaction of the laser light with the electron cloud around the molecule. …

The rest of this article is only available to active members of Questia

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA 8, MLA 7, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Note: primary sources have slightly different requirements for citation. Please see these guidelines for more information.

Cited article

Portable Raman Spectroscopy Systems for Field Analysis
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen
Items saved from this article
  • Highlights & Notes
  • Citations
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA 8, MLA 7, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Search by... Author
    Show... All Results Primary Sources Peer-reviewed

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.