Quantification of Recycled PET in Commercial Bottles by IR Spectroscopy and Chemometrics

• Published in: Analytica Vol. 5; no. 2; pp. 219 - 232
• Main Authors: Zappi, Alessandro, Biancolillo, Alessandra, Kassouf, Nicholas, Marassi, Valentina, Morozzi, Pietro, Tositti, Laura, Melucci, Dora
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.06.2024
• Subjects: Bottles; Centroids; chemometric analysis; Food; Food packaging; Infrared analysis; Infrared spectroscopy; IR spectroscopy; Near infrared radiation; Polyethylene terephthalate; recycled plastic; Recycling; SO-PLS; Spectra; untargeted analysis; VOCs; Volatile organic compounds; United States > US
• ISSN: 2673-4532; 2673-4532
• DOI: 10.3390/analytica5020014

A novel approach for the quantification of recycled polyethylene terephthalate (r-PET) in commercial bottles is presented. Fifty-eight bottle samples from several brands and producers containing different percentages of r-PET were purchased from the market. Samples were analyzed by two spectroscopic methods: near-infrared (NIR) spectroscopy and attenuated total reflection (ATR) spectroscopy in the mid-infrared (MIR) region. No chemical pre-treatment was applied before analyses. The spectra were analyzed by partial-least squares (PLS) regression, and two models for NIR and MIR data were computed. Then, a multi-block regression was applied to join the two datasets. All models were validated by cross-validation and by excluding and projecting onto the model the replicated spectra of one sample at a time. Results demonstrated the potential of this approach, especially considering the variability of commercial samples in terms of additives, shape, or thickness of the bottles: for samples close to the centroids of the models (i.e., from 10 to 50% r-PET), the predictions of multi-block method seldom departed from the expected values of ±10%. Only for samples with 0% declared r-PET, the models showed poor prediction abilities.