Tensor 37 ftir spectrometer

For identification of plastic items from surface sampling, a subset of 38.4% (total: 1075) of all items from field LK and 100% (total: 314) of items from field HB were analysed with a with a Tensor 37 FTIR spectrometer (BrukerOptics GmbH) combined with a Platinum-ATR-unit (BrukerOptics GmbH). Each item was measured after 16 background scans by 16 sample scans (spectral resolution: 4 cm⁻¹ in a wavenumber range of 4000–400 cm⁻¹). Spectra identification was carried out with the internal OPUS 7.0 (BrukerOptics GmbH) database, showing average OPUS-HIT ratios of 619.3 (LK) and 601.9 (HB). For microplastics from soil samples, a subset of 35.4% (total: 99) particles was analysed with a µFTIR spectrometer (Lumos II, BrukerOptics GmbH) with 30 background and 30 sample scans (spectral resolution: 4 cm⁻¹ in a wavenumber range of 4000–680 cm⁻¹). µFTIR spectra were identified using spectra correlation via OpenSpecy^{59 (link)}, resulting in an average r² of 0.84. Each plastic item or microplastic particle, regardless of the spectrometric analysis, was classified according to its visual surface characteristics (particle type, surface form and surface degradation)^{60 (link)}. Statistical operations were performed in Microsoft Excel 2021 (Microsoft), and R (R Core Team, 2020), using RStudio (Version 3.4.1; RStudio Inc.). Spatial data analysis and processing was performed in QGIS⁶¹ .

The NIR spectra were collected with the bare kernels in the diffuse reflectance mode using a Bruker TENSOR 37 FTIR spectrometer (Bruker Optics, Ettlingen, Germany). A fiber bundle was used to illuminate the sample and collect the scattered light. The fiber probe was placed to contact directly with equatorial region of a kernel. Considering the differences in the internal composition of a kernel, the diffuse reflectance spectrum was obtained by averaging the three measurements around the kernel. Each spectrum was the average of 64 scans, and more scans did not reduce the signal noise significantly. The range of the raw spectra was from 12,000 to 4000 cm⁻¹, and the data were measured with an interval of 1.929 cm⁻¹ and a resolution of 4 cm⁻¹, so each raw spectrum has 4148 individual data points. The work temperature was kept at 25°C and the sequence of NIR analysis for all the objects was randomly arranged.

FTIR spectra of the optimized ICA–tocozeinolate nanosphere formula and single formula components (ICA, SDC, TPGS, and zein) were investigated at 4000–400 cm⁻¹ using a Tensor 37, FTIR spectrometer (Bruker, Fremont, CA, USA).