Analysis of organic compounds extracted from recycled polypropylene via GC-FID/MS and Pyr-GC-MS for future pharmaceutical applications

Authors

India E. Hateley

Document Type

Geography, Earth and Environmental Sciences Article

Abstract

A mandatory target for 30% of plastic packaging to be recycled has been proposed by 2030, in order to mitigate the problem of plastic waste being incinerated or deposited in landfills. However, during the recycling process additives are added and with polypropylene being used for plastic packaging and surgical masks, these additives need to be analysed for the presence of contaminants. Examples include VOCs, PAHs, phthalates, and brominated diphenyl’s, all of which have health issues. Two samples of recycled polypropylene pellets were obtained from a national recycling company, along with a reference pellet purchased through Sigma-Aldrich. All pellets underwent ultrasound-assisted extraction (UAE) with three solvents; methanol (MeOH), acetonitrile:methanol (ACN:MeOH 2:1 v/v) and hexane (Hx). The methods used included multiphase (MPE), where all solvents were added to the same vial, and sequential (SE) involved each solvent in separate vials. The analytes were reconstituted with dichloromethane (DCM) before being analysed via gas chromatography-flame ionisation and mass spectrometry (GC-FID/MS) in full scan mode alongside 11 known plastic contaminants, e.g. diethyl phthalate and naphthalene. All three pellets were also analysed via Fourier Transform Infrared Spectroscopy (FTIR), to determine the chemical and physical properties. This confirmed that the pellets were polypropylene due to similar characteristic peaks to the reference pellet. All GC-FID data underwent retention time matching to the standards and confirmed through the GC-MS analysis. The results contained matches from C18-C20 n-alkanes, whilst Hx extracted from C14 onwards. This showed that by using hexane as a sequential solvent it removed all available analytes, whilst MPE did not due to hexane being immiscible in ACN. Main peak differences between all pellets were analysed through the NIST database to find many differences, e.g. 2,6,10,15-tetra-methyl-heptadecane was only present in the recycled pellets and not the reference pellet, meaning it is a by-product of the recycling process. All pellets also underwent analysis through pyrolysis gas chromatography mass spectrometry (Pyr-GC-MS), the thermal degradation of the solid pellet samples resulted in small chain polymer fragments. All differences were analysed through the NIST database to show that VOCs and phthalates were abundant in all, and through statistical analysis of three known peaks present in all, it was found that the reference pellet was significantly different, thus proving the formation of by-products through the recycling process. Only VOCs and dibutyl phthalate was found throughout, therefore, further analysis is needed to obtain the inorganic contaminants present through ICP-MS analysis, to analyse whether or not recycled plastics can be used as packaging for pharmaceutical products.

Publication Date

2025-12

Publication Title

The Plymouth Student Scientist

Volume

18

Issue

2

ISSN

1754-2383

Deposit Date

2025-12

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Recommended Citation

Hateley, India E. (2025) "Analysis of organic compounds extracted from recycled polypropylene via GC-FID/MS and Pyr-GC-MS for future pharmaceutical applications," The Plymouth Student Scientist: Vol. 18: Iss. 2, Article 8.
DOI: https://doi.org/10.70156/1754-2383.1534
Available at: https://pearl.plymouth.ac.uk/tpss/vol18/iss2/8