Microplastics Characterization by Raman Microscopy

Abstract

Identification and quantification of microplastics in the environment is increasingly important. With decreasing particle size, microplastic numbers and therewith the number of species potentially affected by microplastics rise. However, data on the occurrence of small microplastics (<20 µm) in the environment are scarce. Raman microscopy represents an important analytical tool, providing the possibility to close this niche of determining the smallest microplastics. Data on microplastic numbers, their size, shape, and polymer types can be gained. This chapter gives an overview on established applications of Raman microscopy and an outlook on potentially useful future techniques for microplastic analysis. As a basis, the theoretical, physical background of the Raman effect, absorption of infrared light, and the formation of fluorescence is explained. Advantages and disadvantages of Raman microscopy for the detection of microplastics are displayed. Further, all the important methodological steps are discussed: sample preparation to separate microplastics from matrices and to reduce interferences during Raman measurement; the choice of an adequate Raman substrate to achieve good visibility of particles and high quality Raman spectra; measurement parameters and their impact on the results; different measurement modes, such as manual and automatic single particle measurement and Raman mapping, as well as their advantages and disadvantages; prerequisites for representative analysis; and tools for spectral and data interpretation.