Microplastics are everywhere.1 They have been discovered in all areas of the natural environment, within the food chain, and in aquatic organisms, animals, and humans. Clearly, there is an urgent need to identify microplastics in the environment and to better understand how they move through air, soil, water, and into living organisms. Extensive monitoring and studying of microplastics will help address the important questions of their long-term impact on the environment and ecosystems, and if they represent a long-term risk to health.
While visual microscopy has been used extensively, it may be prone to operator error and bias and is limited to larger particles. Vibrational spectroscopic techniques such as Raman and FTIR microscopy provide an alternative, however analysis time can be significant and more rapid and highly automated techniques are desirable.
The quantum cascade laser (QCL) is an alternative infra-red (IR) source that may assist to address this. In contrast to the FTIR approach, a QCL emits IR energy at specific and discrete wavelengths in a collimated beam with all the energy available and can quickly sweep the wavelength range for sub-second acquisition of spectra. Emitting at individual wavelengths, the QCL source can be combined with a single-point detector and rapid scanning optics allowing very fast discrete frequency scanning of large areas. Combined in this way, very fast, highly automated workflows can be achieved.
In this work, we demonstrate why LDIR can be considered an accurate and reliable technique for the identification and characterization of microplastics in a full range of aquatic and marine environment sample-types. The work will also cover how LDIR has been validated for microplastics analysis in terms of identification, particle sizing and differentiating between microplastics and interferences.
1Parker, L., Microplastics have moved into virtually every crevice on Earth, Nat Geog., August 2020, accessed March 2023, https://www.nationalgeographic.com/science/article/microplastics-in-virtually-every-crevice-on-earth