Microscopic Raman-based rapid detection of submicron/nano polypropylene plastics in tea and tea beverages

Area of Science:

• Environmental Science
• Materials Science
• Analytical Chemistry

Background:

• Polypropylene (PP) is a widely used plastic in food packaging, with micro- and nano-PP plastics (MPs) being significant environmental contaminants.
• Current laboratory studies predominantly use polystyrene (PS) spheres, limiting research on the environmental behavior of PP MPs.
• There is a critical need for realistic PP microplastic models and advanced detection methods for accurate environmental assessment.

Purpose of the Study:

• To synthesize micro/nanoscale PP particles (M/NPs) using a top-down approach for enhanced environmental relevance.
• To develop and validate a Raman spectroscopy-based method for qualitative and quantitative detection of PP M/NPs.
• To assess the detection limits of the developed method for various PP M/NP sizes in food simulants.

Main Methods:

• Synthesized negatively charged micro/nano PP particles (203–2101 nm) by controlling solution concentration and volume.
• Integrated Raman spectroscopy and microscopy, utilizing the coffee ring effect, for PP M/NP detection.
• Quantitatively analyzed PP M/NPs in real food media (tea beverages, tea leaves) to determine method efficacy.

Main Results:

• Successfully synthesized PP M/NPs with sizes ranging from 203 to 2101 nm.
• Established a Raman-based detection method with varying limits of detection (LOD) based on particle size.
• Achieved a minimum LOD of 31.25 μg/mL for 203 nm PP nanospheres in tea, and approximately 3.9 μg/mL for larger PP particles.

Conclusions:

• The developed PP M/NP models offer improved relevance for environmental microplastic research.
• The integrated Raman spectroscopy and microscopy method provides a sensitive and accurate tool for detecting PP MPs in complex matrices.
• This study advances the capability to monitor and understand the prevalence of PP microplastics in food and the environment.