Stimulated Raman microscopy for classification of micro-fibers from environmental samples

The assessment of man-made or natural origin of microscopic debris in the environment requires spectroscopical analysis. However, it is difficult to use commercial FT-IR and spontaneous Raman microspectrometers to analyze micro-fibers due to their small size and strong autofluorescence in some specimens. Using a custom stimulated Raman scattering (SRS) microscope, we assessed the origin of microfibers from different environments by comparing their SRS spectra to a home-built library. Our analysis shows that the majority of the analysed micro-fibers are of natural origin. We show that SRS microscopy overcomes the limitations of FT-IR and spontaneous Raman microscopy for classification of micro-fibers.