Near-infrared and Raman spectroscopy Recent developments of portable near-infrared and Raman spectrometers have led to an increase in the use of these techniques for drug quality analysis (Fernandez et al., 2011). Both techniques are nondestructive, fast, and require no sample preparation; radiation can pass through samples in blister packs (Kaur et al., 2010; Martino et al., 2010).
Near-infrared is better suited than mid-infrared to quantitative analysis of drug contents. Computer modeling can produce limited quantitative characterization from all vibrational spectroscopy, but near-infrared and UV-visible spectroscopy yield more reliable quantitative data (Hsu, 1997). Near-infrared can identify active ingredients and is particularly useful for detecting incorrect concentrations of excipients, a common inconsistency in falsified and substandard drugs (Deisingh, 2005). When used with imaging techniques, near-infrared can yield information about a tablet’s composition. Koehler and colleagues demonstrated this by comparing images of a pain relief tablet, one captured using near-infrared imaging and the other not, and illustrating that the homogenous-looking tablet surface actually contained a heterogeneous mix of active and inactive ingredients (see Figure 6-6) (Koehler et al., 2002).