Biomedical Engineering Reference
In-Depth Information
significant spectral differences between the calcifications found in benign and
malignant lesions. For details of the research in this area the reader is referred
to [Chap. 13].
3.4.2 Pharmaceutical Applications
Forensic Applications
An area where SORS has proved to be particularly useful is the authentica-
tion of pharmaceutical products through non-invasive chemical analysis of the
content of opaque plastic bottles and other types of packaging. The method
offers a unique potential to inspect and chemically identify products through-
out the entire supply chain in a non-invasive and non-destructive manner.
The need for such inspection has heightened in recent years with the increase
of counterfeit products on the market [58]. The targeted drugs in the devel-
oped world often include lifestyle drugs and drugs for chronic diseases. More
seriously, in Africa and Asia, it is the essential life-saving medicines, such as
anti-infective drugs, which are plagued by this growing problem [59, 60].
Raman techniques offer an attractive alternative to current methods (prin-
cipally NIR spectroscopy) in which subtle spectral differences in composition
are often hard to detect and chemometric tools are routinely required for data
interpretation. In addition, NIR cannot be deployed non-invasively in many
cases because of the interference and absorption of NIR signal by common
packaging materials. Although conventional Raman spectroscopy has been
used [61], in many instances, and in particular with darkly coloured coat-
ings or capsules, or opaque packaging, the Raman signal of the active phar-
maceutical ingredient (API) can be heavily polluted (or totally masked) by
fluorescence and Raman signals originating from the coating, capsule [45] or
blister pack itself. These interfering signals reduce the sensitivity of the tech-
nique and often preclude the observation of the API and other ingredients
altogether.
Recently Eliasson and Matousek [26, 62] demonstrated that SORS can
provide a chemical signature of the internal content of opaque plastic con-
tainers. This is demonstrated in Fig. 3.11 for aspirin tablets held inside an
opaque (white) plastic pharmaceutical bottle (1.3 mm thick). The conven-
tional Raman signal is overwhelmed by the Raman component originating
from the container wall and is consequently ineffective in determining the
contents of the bottle. In contrast, the SORS method using a scaled subtrac-
tion of two SORS spectra measured at different spatial offsets yields a clean
Raman spectrum of the tablets inside the bottle. SORS has also been used in
the detection of counterfeit anti-malarial tablets by Ricci et al. [63]; the chem-
ical specificity of Raman spectroscopy readily distinguished between genuine
and fake tablets and identified the content of the counterfeit tablets.
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