Raman map

Zhu T., Yu H.Z., Wang J., Wang Y.Q., Cai S.M., Liu Z.F., Two-dimensional surface enhanced Raman mapping of differently prepared gold substrates with an azobenzene self-assembled monolayer, Chem. Phys. Lett. 1997 265 334-340. 

F.C. Clarke, M.J. Jamieson, D.A. Clark, S.V. Hammond, R.D. Jee and A.C. Moffat, Chemical image fusion the synergy of FT-NIR and Raman mapping microscopy to enable a more complete visualization of pharmaceutical formulations. Anal. Chem., 73(10), 2213-2220 (2001). 

An early example of Raman mapping by Breitenbach et al. [52] showed that when crystalline ibuprofen is formulated in a hot melt extrudate the API changes to the amorphous form. Ibuprofen is a sparingly water-soluble compound, so this formulation provides a route to better bioavailability via the more soluble amorphous form. Using confocal Raman mapping the form of the API was determined at the time of manufacture and under stress conditions and was used to assess the stability of the amorphous form. These studies also showed that the API was homogeneously distributed throughout the formulation based on the relative band intensities of the amorphous API and a formulation excipient, polyvinylpyrrolidone (PVP). 

Despite these limitations the ability to obtain information from tablets (and other solid dosage forms) about the location and form of excipients and API non-destructively using Raman mapping approaches is second to none. 

Although the use of Raman mapping has clear benefits to the analysis of inhaled product, the approach has a number of limitations. These include... 

Fig. 11.4. A Photomicrograph of a histological tooth section ( 100 i.m) in the region of sound and carious enamel. Area mapped is outlined by the rectangle. B The corresponding Raman map of the 959 cm-1 phosphate peak intensity...

With the help of a micro-Raman setup the laser spot can be focused down to about 1 pm in diameter. This allows for the differentiation of single bacterial cells or a biochemical analysis of subcellular components within bacterial (diameter approx. 1 pm) or yeast cells (diameter approx. 5-10pm). A confocal Raman setup achieves an even better spatial resolution [6, 7]. This possibility enables Raman mapping or imaging experiments with spatially resolved information of the whole sample in axial and lateral directions. 

Clarke, F.C. Jamieson, M.J. Clark, D.A. Hammond, S.V. Jee, R.D. Moffat, A.C., Chemical Image Fusion. The Synergy of FT-NIR and Raman Mapping Microscopy to Enable a More Complete Visualization of Pharmaceutical Formulations Anal. Chem. 2001, 73( 10), 2213-2220. 

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