Overcoming the challenge of quantifying aged microplastic by qNMR spectroscopy

Area of Science:

• Environmental Science
• Analytical Chemistry
• Materials Science

Background:

• Microplastic pollution poses a significant environmental threat.
• Accurate quantification of aged microplastics is crucial for environmental risk assessment.
• Existing methods struggle to quantify aged synthetic microplastics effectively.

Purpose of the Study:

• To evaluate quantitative nuclear magnetic resonance (qNMR) for quantifying aged microplastics.
• To assess the impact of UV exposure and elevated temperatures on polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET).
• To integrate qNMR with SEM and FTIR for a comprehensive analysis of microplastic aging.

Main Methods:

• Microplastics (PS, PVC, PET) were aged under UV and heat for 24 days.
• Quantitative nuclear magnetic resonance (qNMR) was used for quantification.
• Scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy assessed physical and chemical changes.

Main Results:

• qNMR showed consistent signals for aged vs. pristine microplastics with low quantification errors (1-18%).
• SEM revealed surface degradation in PS and PVC, FTIR indicated oxidation (increased carbonyl index), while PET showed minimal changes.
• Degradation products in PS and PVC were quantified; PET showed no significant degradation.

Conclusions:

• qNMR is a sensitive and reliable method for quantifying aged microplastics.
• Combined qNMR, SEM, and FTIR provide detailed insights into microplastic aging processes.
• This approach supports the development of robust methods for environmental microplastic monitoring.