How microplastics are measured

Match the method to the result

Raman and FTIR can provide chemical information about polymer material. Microscopy also records particle appearance or size, but fluorescent or visible objects need an identification workflow before they can be treated as chemically identified plastic particles. ¹²

Nile Red staining and confocal imaging supplied counts in the food-wrap study, while characterization of the bulk film was performed separately. Keep that distinction visible rather than calling the counted objects individually Raman-confirmed. ³

Keep counts and mass separate

A polymer-mass result cannot be converted to a particle count without information about the particles. Area-normalized counts, counts per container, and chemical concentrations answer different questions. The source studies retain those denominators. ¹³⁴

Read the controls and size window

Check how laboratory contamination was controlled, whether blanks were processed, which particles were retained, and how polymer identity was established. Sample preparation and aggregation can affect what is counted. A filter’s pore size is not automatically a validated analytical detection limit. ¹

What remains uncertain

These method descriptions explain the reviewed studies. They do not establish a universal food-storage test or make results from unlike methods interchangeable.

What the supplied water methods add

The California IR procedure states a lowest reliably detected size of 50 µm; the Raman procedure states 20 µm. Both apply to treated drinking water within their specified procedures. These values do not describe all FTIR or Raman instruments and do not establish a nanoplastic detection capability.⁵⁶

The EU water decision combines morphology or chemical mapping with polymer identification. It distinguishes particle-number measurements from mass-only thermal measurements. JRC practical guidance explains why blanks, recovery, sizing and reporting are essential, and why extension to another matrix requires evaluation.⁷⁸

References

1. Detecting Micro- and Nanoplastics Released from Food Packaging: Challenges and Analytical StrategiesClaudia Cella, Rita La Spina, Dora Mehn, Francesco Fumagalli, Giacomo Ceccone, Andrea Valsesia, Douglas Gilliland · Polymers · 2022 · DOI: 10.3390/polym14061238Research article
2. An Insight into the Growing Concerns of Styrene Monomer and Poly(Styrene) Fragment Migration into Food and Drink Simulants from Poly(Styrene) PackagingAsmaa Ajaj, Shayma J’Bari, Anthonia Ononogbo, Federico Buonocore, Joseph C. Bear, Andrew G. Mayes, Huda Morgan · Foods (Basel, Switzerland) · 2021 · DOI: 10.3390/foods10051136Research article
3. Rapid Generation of Microplastics and Plastic-Derived Dissolved Organic Matter from Food Packaging Films under Simulated Aging ConditionsLiuwei Wang, Jing Gao, Wei-Min Wu, Jian Luo, Michael S. Bank, Albert A. Koelmans, John J. Boland, Deyi Hou · Environmental science & technology · 2024 · DOI: 10.1021/acs.est.4c05504Research article
4. Quantitative analysis of polystyrene microplastic and styrene monomer released from plastic food containersJiae Wang, Jieun Lee, Eilhann E. Kwon, Sanghyun Jeong · Heliyon · 2023 · DOI: 10.1016/j.heliyon.2023.e15787Research article
5. SWB-MP1-rev1: Infrared spectroscopy of microplastic particles in drinking waterCalifornia State Water Resources Control Board and SCCWRP · Official document · 2022 · Official sourceOfficial method
6. SWB-MP2-rev1: Raman spectroscopy of microplastic particles in drinking waterCalifornia State Water Resources Control Board and SCCWRP · Official document · 2022 · Official sourceOfficial method
7. Commission Delegated Decision (EU) 2024/1441: methodology to measure microplastics in water intended for human consumptionEuropean Commission · Official document · 2024 · Official sourceLegal instrument
8. Analysing microplastics in drinking water: Practical considerationsDora Mehn, Claudia Cella, Guillaume Bucher, Francesco S. Fumagalli, Hind El Hadri, Douglas Gilliland · Official document · 2025 · DOI: 10.2760/1240697Technical report