Supporting Drug Development Process with Raman Spectroscopy
Kathleen A. Martin
Drug Discovery & Development - December 11, 2014
Raman spectroscopy has steadily gained a wider role in the pharmaceutical industry because of its applicability to several important aspects of drug development and manufacturing. Among its applications are the identification of polymorphs and hydrates, the elucidation of reaction mechanisms, mapping the distribution of ingredients in solid dosage forms, process control during manufacture, identification of contaminants, and the detection of counterfeit drugs. Three of these applications, identification of polymorphs and hydrates, mapping of tablet ingredients, and identification of contaminants, will be briefly discussed here.
How Raman spectroscopy works
Raman spectroscopy produces data that reflect the molecular and crystalline structures of materials and thus can be used for the identification or characterization of materials. The Raman effect is based on the inelastic scatter of light from a sample. When a light source such as a laser is focused on a sample, the vast majority of the light is scattered at the same wavelength as the incident light (Rayleigh scatter). A very small amount, however, may be scattered at a slightly longer wavelength (inelastic scatter). The difference in wavelength between the incident light and inelastically scattered light is called the Raman shift and corresponds to the energy of vibration of a molecular group or crystal lattice mode. A Raman spectrum, therefore, is analogous to an infrared spectrum, although the two spectroscopies provide information about different aspects of molecules.