Instrument: Bruker RAM II
Similar to FT-IR, Raman spectroscopy is a vibrational spectroscopic technique which allows compositional analysis of liquids and solids. The technique can be used to analyse a range of samples (organic and inorganic) to determine structural/compositional changes and for identification of unknown samples.
Raman spectroscopy can also be used as an informative and sensitive imaging technique and this technology, which is also available in JBL Science is covered here
Inelastic scattering (Stokes/ Anti-Stokes scattering) of visible light, corresponding to molecular polarizability changes due to molecular vibration (e.g. asymmetric bond stretching) result in a unique absorption spectrum for each compound of interest.
Raman is an identification technique which allows specific chemical bonds in a sample to be determined. Consequently Raman is useful as part of formulation studies or examination of unknown samples to determine the presence of compounds of interest e.g. active pharmaceutical ingredients (APIs).
In addition to determining composition, the technique allows the crystallographic structure of a sample to be determined. This polymorphic information is essential in pharmaceutical studies and can also be used to investigate the crystal structures in mineral and metallurgical samples.
By combining the technique with microscopy, spatial chemical resolution can be performed to determine the heterogeneity of a sample. In addition, depth profiling can be carried out to perform 3D studies to look at the penetration of a chemical through a sample e.g. transdermal drug delivery studies.
Raman spectroscopy can be carried out on both solid and bulk liquid samples although spatial resolution is only possible on solid samples. Flat sample surfaces are required in order to ensure consistent sample focus to perform spatial mapping studies. Samples should be small enough (or at least be able to be processed to be small enough) to fit on a microscope stage.