eBook: Raman Imaging in Pharmaceutical Research - 7

Nadu, India).3
The tablet was microtomed in order
to analyze its interior without interference from
the coating.
The Raman image of the tablet visualizes the distribution
of its five components, which are color coded
according to their Raman spectra (Figure 3A). The
tablet contained the APIs metformin and glimepiride,
with metformin being the main component of
the tablet and glimepiride a low-dosage drug. It further
contained lactose monohydrate as a diluent,
polyvinylpyrrolidone (PVP) as a binder and magnesium
stearate as a lubricant. Glimepiride was detected
although it accounted for less than 0.1 % of the
recorded 4 mm² area (Figure 3B). Its ability to detect,
identify and quantify APIs and excipients even in
such small dosages makes Raman imaging a promising
technique for pharmaceutical investigations.
References
1. N. Jung and M. Windbergs, Raman spectroscopy in
pharmaceutical research and industry. Phys. Sci. Rev. 3: 20170045
(2018). DOI: 10.1515/psr-2017-0045
2. T. F. Haefele and K. Paulus, Confocal Raman microscopy in
pharmaceutical development. In: Confocal Raman Microscopy, J.
Toporski, T. Dieing, O. Hollricher (eds.). Springer Series in Surface
Sciences 66, Springer International Publishing AG, 2nd ed., pp.
381-419 (2018). DOI: 10.1007/978-3-319-75380-5_16
3.
A. Venkatesan, A. Radhakrishnan, G. Kuppuswamy, S. Kumar
Singh, Detectability & quantification of low-dose glimepiride in
a fixed-dose combination using Raman imaging. Vib. Spectrosc.
113: 103229 (2021). DOI: 10.1016/j.vibspec.2021.103229
Raman Effect
The Raman effect is based on light interacting with the chemical bonds of a sample. Due to vibrations
in the chemical bonds the interaction with photons causes specific energy shifts in the back scattered
light that appear in a Raman spectrum. The Raman spectrum is unique for each chemical composition
and can provide qualitative and quantitative information of the material.
Raman spectroscopy
* provides a chemical " fingerprint " of the investigated compounds
* is non-invasive, non-destructive, label-free
*
*
requires minimal, if any, sample preparation
is insensitive to water
* can be used for imaging
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eBook: Raman Imaging in Pharmaceutical Research

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