What Happens During and After the Laser Scatter Process?

This week I journeyed back to the laser lab to try out a few new items that came in--with moderate to good success--and I wanted to show you what happens during the laser scatter process and how I take the information from the Raman spectroscope and how I make it meaningful. 

When a particle is exposed to the laser, it scatters light in a unique way based its chemical composition. Thanks to the diligence of researchers, I have access to databases of known materials to compare my laser scatter data to. Take, for example, the initial laser scatter pictured here. You can see a few characteristic peaks, but there is also a lot of space that is noise (for example between 1200 and 2000. Noise is generated by dust or other materials that may interfere with the laser during the process, and needs to be removed before I can accurately process the samples. Luckily, again, researchers have developed methods to smooth out the laser scatter data to make it more meaningful, pictured below. You can see the yellow uploaded spectra overlaid with the processed spectra, where noise is normalized and the characteristic peaks are amplified. From here, I compare this processed spectra to known spectra of materials that have been tested by labs throughout the world to determine what the particle is made of. I also generate a correlation coefficient that you can think of as a percent match in this situation. The particle that is represented by these data had a correlation coefficient of .83 (out of 1.00) to one of the known materials in the database. Turns out this material was a microplastic, but even if it wasn't, the database would provide the best matches with their correlation coefficients for any material in the database that the spectra could represent.

The whole process, from isolating a particle to processing and finding the particle's most likely composition, takes approximately 8 minutes, and with nearly 600 particles to process, I will be quite busy. However, laser analysis must take a backseat, as I will be going out into the field next week to collect the final samples for the first section of my research, and I will again be busy processing and extracting microparticles from the samples. Tune in to see how muddy my research team and I get!

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