Ft ir spectrum frontier spotlight 400 microscopy system

Depositions collected during the polystyrene degradation assay were dried at 37 °C overnight and then inspected with a dissection microscope before being analyzed using an FT-IR Spectrum Frontier/Spotlight 400 Microscopy System (Perkin Elmer, Shelton, CT, USA). Images were taken in attenuated total reflection sampling mode (ATR) with 1.56 µm pixel size, 6 cm⁻¹ spectral resolution, 16 scans per image, and an ATR and atmospheric correction using the supplier software SpectrumIMAGE R1.7.1.0401. The resulting spectra data hypercube was then unfolded to a 2D matrix, which was then subjected to a principal component analysis (PCA) to determine the probable number of components in the samples (for the following analysis). A second chemometric analysis was carried out for spectral deconvolution to obtain the “pure” spectra and localization of the main chemical components in the image, using multivariate curve resolution with an alternating least squares algorithm (MCR-ALS). Pure algorithm was used as initialization, and a non-negativity constraint was applied in both spectra and concentration. All analyses were performed in Matlab (R2018b, Mathworks, Natick, MA, USA) using a MCR-ALS toolbox [20 (link)].

FT-IR spectra and images of pulps were analysed by micro-FT-IR using an FT-IR Spectrum Frontier/Spotlight 400 Microscopy System (PerkinElmer, Inc. Waltham, MA, USA) with a linear array of mercury cadmium telluride (MCT) detectors. Areas between 45 µm × 70 µm and 70 µm × 60 µm of isolated fibres previously dried for 8 h at 45 °C were scanned by attenuated total reflectance (ATR), using a germanium crystal as the high reflective material, a pixel size of 1.56 µm × 1.56 µm, and a spectral range of 1000 to 1800 cm⁻¹ with a spectral resolution of 8 cm⁻¹ and 16 scans per spectrum. The spectra extracted from the images were subjected to ATR correction, removal of atmospheric noise, and baseline correction, and transformed to absorbance before imaging and chemometric analysis.