Confocal Raman microscopy is a great technique for microplastics as it is non-contact and non-destructive, the observation can be made simply using low power objectives over a wide field of view, or with a high power objective on smaller particles. Mixed samples including inorganics can be identified.  Spectral libraries can be used for component identification.

IR Microscopy is probably more suited to large particle sizes, greater than 10 microns. The transmission allows for reduced sample prep and non-contact sampling, but ATR is also useful for mapping larger particles and for mixed polymer materials. The larger IR spectral databases of organic substances is a major attraction to users when identifying unknown foreign materials.

ATR offers a “preparation-free” measurement of samples and is ideally suited to plastic particles as they deform well and make good contact with the prism under pressure. Diamond is an excellent prism material as it is virtually indestructible and is transparent to visible light, which can be used for sample observation. For microplastics that are large enough to be measured without a microscope, chemical identification is easy with a typical ATR, and the ATR Pro 4X View also provides a visual record of the particles being measured.