Forensic Analysis of Drugs

On-site analysis of substances can make a job much easier for those responding to an emergency and for those investigating a scene where unknown substances are found. Since many illegal drugs and chemical weapons look similar to other innocuous substances, it is useful to have the ability to make quick and reliable identifications of the unknown materials.

Both FTIR and Raman are useful in identifying narcotics. Raman has the advantage of minimal sample preparation. Also, its ability to analyze substances through their containers make it a convenient method to use in the field as well as in the lab. Since many drugs contain more than just a single type of molecule, the combination of Raman and FTIR complement each other well for this application.

Raman techniques are being studied for use in identifying counterfeit pharmaceuticals. One study analyzed the Raman technique for its effectiveness in this area. (17) Authentic and suspect tablets were analyzed by both FTIR and Raman in order to compare both their coatings and their cores. The figure below shows that the combination of techniques can give a much more complete picture.

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The FTIR picked up mainly the organic components of the tablet coating. The Raman picked up mostly the inorganic components. Raman's ability to obtain spectral data below 600 cm^-1 makes it very useful in identifying the inorganic species. Most IR spectrometers are not sensitive in this area.

One other advantage Raman has over FTIR is that water is transparent to Raman. The water molecule has strong absorptions in the IR spectrum, making it very difficult to analyze substances in any kind of aqueous environment. Since water does not strongly absorb in Raman spectroscopy, this environment is not a problem for Raman. This opens the door to in vitro and in vivo analysis of drugs in human fluids or tissues. (18) Raman can be used to study various layers of human skin without invasive methods. FTIR has also been studied in this use. (19) Both of these areas are very new and require further research, though advances in the associated technology have made them very realistic goals. (18,19) Raman, however, can also be used for in vitro studies of bodily fluids. (18) Its insensitivity to water means that samples do not need to be extracted from bodily fluids before analysis. This greatly increases the usefulness of the method in the lab.

Though FTIR is an established analytical method for identifying drugs, the additional Raman method helps paint a more complete picture.

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