Can Raman be used for macro/bulk analysis?

Yes. Macro and bulk analyses are straightforward with modern Raman systems.

Bulk solutions (organic and aqueous) typically require just a simple cuvette cell holder and collection/focusing optics.  It is also possible to analyse directly into sample bottles and vials using confocal optics, which minimise the contribution of the glass container to the spectrum.

Gas samples are more difficult and the success generally will depend on the type of gaseous sample under investigation and its pressure.  Typically gases have much lower concentrations, which means weaker Raman signals.  Examples of more straightforward gas measurements include gaseous inclusions within minerals, and headspace analysis in pharmaceutical vials.

Macro solid samples can also be analyzed but typically this will require a relatively large laser illumination area in order to give an average spectrum from a large area.  HORIBA Scientific’s DuoScan™ optics allow the user to define a laser spot size on the sample – it can thus be used for true microscopic analysis with <1 µm spot diameters, as well a bulk analyses with analysis areas up to 270 x 270 µm2.

Raman systems can also be configured with macro chambers, which have special optics designed for large area macro or bulk analysis.

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