Since the plastic samples were taken from consumer sources, their exact type was presumed to be unknown despite accompanying labels (provided for recycling instruction). Many commercially available plastics are proprietary blends of a polymer with fillers, dyes, and plasticizers and so to correctly identify the samples, their chemical nature was identified using two spectroscopic techniques: Fourier transform infra-red spectroscopy (FTIR) and Raman microscopy (µ-Raman). Almost all of the samples had clearly identifiable FTIR spectra, with notable exceptions being Neoprene (polychloroprene) and tire-rubber composite. Although the chemical structure could be adequately described with the aid of prior knowledge of the materials source, the presence of dyes and fillers produces a range of peaks that would not be present in pure samples. Particularly for the tire rubber, highly absorptive fillers such as carbon black dramatically shift the spectrum baseline. To complement the FTIR analysis, Raman microscopy (µ-Raman) was used on all of the samples to confirm their identification and whether there was any spatial heterogeneity in their composition, either by the presence of dyes or additives. To investigate this, µ-Raman spectra were taken from different regions of MPs as well as from different individual MPs. No significant differences in the spectra were observed within or between particles which indicates, unsurprisingly, that the plastics are highly homogenized during production.