Some Advances in Fourier Transform Infrared Transflection Analysis and Potential Applications in Forensic Chemistry

Abstract

The transflection technique offers significant potential for both qualitative and quantitative analysis in the mid-infrared region. The higher sensitivity for bands in the mid-infrared provides a distinct advantage over the lower absorbance values typically encountered in the near-infrared region. Other advantages, such as small sample size and little sample preparation, make this technique a good candidate for the analysis of forensic substances. Small amounts of illegal drugs such as cocaine can be reliably and nondestructively identified with little or no sample preparation. With the approach to transflection described in this paper, single grains can be quickly identified by simply placing the sample on a specially designed substrate and recording the Fourier transform infrared (FT-IR) spectrum. Transflection was applied to the qualitative analysis of aqueous solutions and solid particles using relatively simple equipment in conjunction with a commercially available diffuse reflection accessory. Improvements in both equipment and technique are discussed. Extensions of the equipment into two new forms, with potential uses in proteomics and forensics, are introduced.

Rapid Presumptive “Fingerprinting” of Body Fluids and Materials by ATR FT‐IR Spectroscopy*,†

“…There is no published presumptive forensic test for breast milk, tears, or nasal mucus. Infrared (IR) spectroscopy is an accepted method used to evaluate evidence such as alcohol, drugs and other white powders and derivatives, inks, fibers, anodization treatment and surface oxides, paints, and primers (http://www.sigmaaldrich.com/labware/products/sensir-atrlibrary.html; http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_ frame_top.cgi) (18)(19)(20). IR spectroscopy is also used for the identification of nerve and blister agents, industrial chemicals, weapons of mass destruction, chemical precursors, common household and laboratory chemicals, solvents, explosives, and propellants (http://www.sigmaaldrich.com/labware/products/sensiratr-library.html; http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_ frame_top.cgi) (21)(22)(23).…”

Historical perspective and modern applications of Attenuated Total Reflectance – Fourier Transform Infrared Spectroscopy (ATR‐FTIR)

“…[20,21] Field-based ATR-FTIR instruments are also used for the detection and more importantly identification of chemical warfare agents including nerve and blister agents. When hand-held ATR-FTIR instruments are used, these kind of applications can be carried out directly on the scene.…”

Infrared attenuated total reflection (IR‐ATR) spectroscopy for detecting drugs in human saliva

“…Koçak et al analyzed solid cocaine.HCl with infrared transflection spectroscopy. [7] However, an accurate comparison is not possible since not all peaks in those references are given with their exact position. In Table 1 the positions of the main peaks in Figure 2 are compared with literature data.…”

“…and Lopéz‐Artíguez et al . Koçak et al . used Fourier transform IR transflection spectroscopy to investigate solid cocaine.HCl.…”

“…For determining the origin of illicit cocaine samples, solid cocaine is investigated with a number of methods. IR spectroscopy on pure and diluted solid cocaine has been employed by Koulis et al [4,5] and Lopéz-Artíguez et al [6] Koçak et al [7] used Fourier transform IR transflection spectroscopy to investigate solid cocaine.HCl. Furthermore, the differentiation between Pseudoecgonine and Ecgonine (Ecgonine is also metabolized by the body after cocaine consumption) is very helpful in determining the origin of illicit cocaine.…”