Author: Dr. Wilifried Carl, R&D Director Sika Sarnafil
Sika Sarnafil's Canton R&D lab uses a Raman spectrometer as a universal analytical tool when it comes to identification of foreign material, control of incoming raw materials, analysis of competitor products, etc.
The Raman effect itself is a so-called quantum mechanical effect and has been discovered 1928. It is only in the last years that, with the progress in laser technology, small Raman spectrometers have become available at a very reasonable price, so that they made their way into the R&D labs of many companies.
The measuring principle can be described without any knowledge of quantum mechanics, since it is basically a measurement of intensity of scattered light. Everyone knows what it looks like when driving at night on a foggy road: your car’s headlights will lead to intense white glow of the fog: this is light scattering (because the small drops forming the fog have just the right size). A Raman spectrometer does exactly the same thing. A material sample is illuminated by a laser and the scattered light is analyzed. The only difference is that Raman scattering shifts the frequency, and thus the color of the light. If you drive in a foggy night and see your white headlights illuminate the fog in various colors, it is very likely not Raman scattering, but an UFO.
The spectrum below shows a series of peaks; since it is very involved to relate each of them to a particular molecular structure, one normally takes this as a so-called fingerprint spectrum. By comparing Raman spectra of two substances (say, two raw materials, or an unknown material with a known material), it can be decided if they are identical (same spectrum) or not (different spectrum).
This is what the principle looks like:
And this is how the machine looks in reality:
And this is a Raman spectrum: