Spectroscopic imaging with Raman spectroscopy

Infrared and Raman spectroscopy provide complementary images of molecular vibrations, because in these spectroscopic techniques the mechanisms of the interaction of light quanta with molecules are quite different. 

Infrared spectroscopy performed both in the mid-IR [70] and near-IR [71] provides the potential of rapid determination with little or no sample preparation. Raman spectroscopy also has demonstrated capability for pharmaceutical analysis [72], Vibrational spectroscopic techniques are effective for compositional and structural characterization, as well as quantitation. However, bulk spectrosocpy is ineffective for measuring the spatial distribution and architecture of actives, which are heterogeneously distributed within intact tablets. Raman chemical imaging equipped with multivariate image processing capabilities is a powerful approach to the analysis of pharmaceutical tablet architecture. 

Although a combination of spectroscopy imaging e.g. /xXRF, /xFTIR, /xRS) would offer a powerful way to characterise materials various hurdles must be overcome to achieve the ultimate in integrated spectroscopic imaging. These difficulties include spatial resolution, specimen preparation, spectroscopic probe penetration depth and image integration. Same-spot (optical, /u-FTIR, /u.RS) technology is now available. The topic of Raman microscopy in combination with other microanalysis techniques (electron microscopy/X-ray microanalysis ion mi-croprobe mass spectrometry, and laser microprobe mass spectrometry), i.e. dual-use microprobe systems, has been discussed [534]. 

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