NCJ Number
215073
Journal
Forensic Magazine Volume: 3 Issue: 3 Dated: June/July 2006 Pages: 15-16,18,20
Date Published
June 2006
Length
5 pages
Annotation
This article discusses the benefits of using a Fourier Transform Infra-red (FTIR) spectrometer to analyze explosive residue samples in a forensic laboratory.
Abstract
The spectroscopic identification of explosive materials by FTIR is attractive due to the inherent capabilities of real-time identification, nondestructive analysis, and minimal sample preparation. These advantages are maximized when reflection sampling accessories are used. As a result of the increase in the speed, the decrease in size, and declining price of personal computers, the FTIR has become the spectrometer of choice over dispersive instruments in the mid-infra-red region. The main advantages of FTIR spectrometers over dispersive instrumentation are the use of a laser as an internal standard to provide high accuracy; that no slits are required, which allows all the energy of the source to pass through the interferometer to the sample; and that all the wave numbers in a spectrum are collected simultaneously. Also, computerized alignment and electronically dehumidified interferometers have improved the level of reliability and the ease of use of these systems. This article also compares the sampling techniques of transmission (direct and diffuse), specular reflectance, diffuse reflectance, and attenuated total reflectance. The article concludes with a discussion of the importance of FTIR microscopy, which creates a two-dimensional spatial map or "image" of a suspected explosive material on crime scene evidence. FTIR microscope systems can collect spectra by the full range of sampling techniques. 5 figures