Non-invasive probing of pharmaceutical capsules using transmission Raman spectroscopy

We demonstrate how transmission Raman geometry can be effectively used for non-invasive probing of the content of pharmaceutical capsules. This approach is particularly beneficial in situations where the conventional Raman backscattering method is hampered or fails because of excessive surface Raman or fluorescence signals emanating from the capsule shell material, which pollute the much weaker subsurface Raman signals with undesired noise. It is demonstrated that such interfering signals can be effectively suppressed by the transmission geometry. The ability to avoid surface fluorescence and Raman signals in conjunction with the superior, bulk-probing properties of the transmission Raman geometry provides an analytical technique ideally suited for fast on-line process control monitoring applications in pharmaceutical industry where rapid, chemically specific bulk analysis is required. Copyright (C) 2007 John Wiley & Sons, Ltd.