Xplora nano raman microspectrometer

RMS analysis was performed by using an XploRA Nano Raman Microspectrometer (Horiba Scientific) at the ARI Laboratory of Università Politecnica delle Marche (Ancona, Italy). All filter membranes, including those deriving from the procedural blanks, were inspected by visible light using a ×10 objective (Olympus MPLAN10×/0.25). The detected MPs were morphologically characterised by a ×100 objective (Olympus MPLAN100×/0.90) and then directly analysed on the filter by RMS (spectral range 200–1800 cm⁻¹, 532 nm or 785 nm laser diode, 600 lines per mm grating). Spectra were dispersed onto a 16-bit dynamic range Peltier-cooled CCD detector; the spectrometer was calibrated to the 520.7 cm⁻¹ line of silicon prior to spectral acquisition. To reduce noise and enhance spectrum quality, raw Raman spectra were subjected to polynomial baseline correction and vector normalisation (Labspec 6 software, Horiba Scientific). The polymer matrix of the detected particles was identified by comparing the collected Raman spectra with spectral libraries of polymers and pigments obtained by measuring standard polymers/compounds (KnowItAll software, John Wiley & Sons, Inc., Hoboken, NJ, USA) [28 (link),29 ]. Similarities of more than 80 of the Hit Quality Index (HQI) were considered satisfactory.

Raman microspectroscopy (RMS) analysis was performed at the ARI Laboratory of Università Politecnica delle Marche (Ancona, Italy); an XploRA Nano Raman Microspectrometer (Horiba Scientific) was exploited. A first visible screening of all filter membranes, including those deriving from procedural blanks, was performed by a ×10 objective (Olympus MPLAN10×/0.25, Tokyo, Japan). Thus, the morphology of the detected MPs was characterized by a ×100 objective (Olympus MPLAN100×/0.90, Tokyo, Japan). Then, MPs were submitted to RMS analysis directly on the filter by using a 532 nm or 785 nm laser diode (spectral range 200–1800 cm⁻¹; 600 lines per mm grating). Spectra were dispersed onto a 16-bit dynamic range Peltier-cooled CCD detector; before the spectral acquisition, the calibration of the spectrometer was performed on the 520.7 cm⁻¹ line of silicon.
All raw Raman spectra were submitted to polynomial baseline correction and vector normalization, to decrease noise and improve spectrum quality (Labspec 6 software, Horiba Scientific). Finally, the Raman spectra collected for each MP were compared with specific spectral libraries of polymers and pigments (KnowItAll software, John Wiley & Sons, Inc., Hoboken, NJ, USA) to identify the polymer matrix [34 (link),35 ]. Values of the Hit Quality Index (HQI) greater than 80 were considered satisfactory.