High-throughput environmental microplastic identification and quantification using a wide-field QCL-IR based microscope

Microplastics (MP) have been found all over the planet and it is quite difficult to model the impact on the biosphere due to the low throughput of conventional measurement techniques. They actually restrict the number of measurable samples in appropriate time frames. Even the fastest conventional methods to quantify MP such as Fourier-Transform-IRmicroscopes (μFTIR) or Raman microscopes do not provide the required speed for measuring the desirable number of samples. By combining a wide field quantum cascade laser (QCL) based microscope with an automated vibrational spectroscopy data base (siMPle) identification and quantification of the particles fit into normal laboratory routine time slots. The MIDIR transmission spectra of environmental samples on standard and cost-effective Aluminum oxide filters were measured and evaluated using the adaptable data base design1 2 . The results turned out to be very similar to the common techniques, and particles assigned by FT-IR to one material, were connotated to the same using the laser-based method. Furthermore, the spatial resolution of the laser-based system is slightly superior to the one of μFTIR and the size distribution determined was found similar to results from even slower Raman-microscopy especially for small particle size smaller than 50 μm. Amongst others a treated waste water sample of 12*12 mm2 was measured in less than 36 minutes delivering 8,294,400 spectra with 2 cm-1 resolution, while the time to analyze the data remains the same order of magnitude, the pure measurement is more than ten times faster compared to using state of the art FT-IR-microscopes.