Towards harmonization of metal(loid)s determination in conventional and compostable plastics : comparison of acid digestion protocols in LDPE and PBAT/TPS blends

Carnati, Stefano (author), Pozzi, Andrea (author), Spanu, Davide (author), Bettinetti, Roberta (author), Nizzetto, Luca (author), Kalčíková, Gabriela (author), Botta, Ludovica (author), Binda, Gilberto (author)

The determination of metal-containing additives in plastic materials via acid digestion protocols has attracted growing interest to address potential environmental implications. However, the lack of protocol harmonization hinders data comparability within the literature. Here, six acid digestion protocols were employed to determine the metal(loid) content in plastics: these included three different acid mixtures (HNO$_3$ combined with H$_2$SO$_4$, HCl or H$_2$O$_2$) for microwave-assisted digestion, with or without an additional room-temperature digestion step with H$_2$O$_2$. Each protocol was first validated for seven metal(loid)s (As, Cd, Cr, Pb, Sb, Sn and Zn) using a low-density polyethylene (LDPE) certified reference material (ERM®-EC681m). Then, validated protocols were applied on end-use materials, including conventional (i.e., LDPE) and compostable (i.e., PBAT/TPS) plastics. The combination of H$_2$SO$_4$ and HNO$_3$ with a further digestion step with H$_2$O$_2$ was the most suitable protocol: it successfully passed validation thresholds for all metal(loid)s (recoveries in the range 98.6–101.0 %) and yielded the highest concentrations in end-use materials. All other protocols resulted in a less efficient digestion of the sample matrix, leading to lower recoveries and the formation of solid residues. Notably, end-use plastics showed a great variability in metal(loid) concentrations, likely due to their additive-rich composition, in contrast to the minimal content of acid-soluble additives of the reference material. This study represents an initial step towards the harmonization of acid digestion protocols and highlights new challenges in accurately analyzing end-use plastic materials, due to their complex additive composition.

• Language: English
• Keywords: polymers, metals, metalloids, acid digestion, additives, microplastics
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2024
• Number of pages: 10 str.
• Numbering: Vol. 367, art. 143581
• PID: 20.500.12556/RUL-164610
• UDC: 543.632.495:678
• ISSN on article: 0045-6535
• DOI: 10.1016/j.chemosphere.2024.143581
• COBISS.SI-ID: 213674499
• Publication date in RUL: 05.11.2024

Record is a part of a journal

• Title: Chemosphere
• Shortened title: Chemosphere
• Publisher: Elsevier
• ISSN: 0045-6535
• COBISS.SI-ID: 25213696

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: polimeri, kovine, metaloidi, kislinska razgradnja, aditivi, mikroplastika