Detecting Environmental Microplastics and Nanoplastics With Spectroscopy

One important area in environmental monitoring is the study of microplastics, which are tiny plastic particles resulting from decomposition of plastic substances that are ubiquitous in the environment. Because microplastics pose ecological and health risk to both humans and wildlife, researchers have investigated new methods for detecting and classifying microplastic concentrations in the environment.

In this tutorial article, we review the latest in microplastic analysis, highlighting the techniques that have been frequently used in this space and where they have been most effective.

Q: Why have spectroscopic techniques become the primary tools for studying micro- and nanoplastics (MNPs) in the environment?

Microplastics (MPs) and nanoplastics (NPs) are pervasive pollutants. They have been found in marine and terrestrial ecosystems, drinking water, and even human bodies.¹ Because these particles are often smaller than 5 millimeters, and sometimes nanoscale, they are difficult to detect using traditional visual methods.^1–3 Assessing microplastic concentration, therefore, requires reliable analytical tools. Because of this need, spectroscopy has played a key role in this pursuit. Spectroscopic techniques are preferred because they provide precise identification and characterization of a particle's chemical composition, morphology, and size without destroying the sample.^1,3 This allows scientists to understand exactly what type of polymer is present and where it might have originated.³

Q: What is the most widely used spectroscopic method for identifying microplastics today?

There are several spectroscopic techniques that are routinely used for identifying microplastics. However, the most common method used is Fourier transform infrared (FT-IR) spectroscopy. FT-IR spectroscopy works by measuring how plastic particles absorb infrared light, creating a unique "fingerprint" for different polymers.¹ There have also been several key recent advancements that have improved this technique. For example, the integration of focal plane array (FPA-FT-IR) has significantly increased data collection speeds.¹ This integration has facilitated unbiased, automated analysis of large quantities of particles without the need for manual presorting.¹ Additionally, researchers have developed ways to attach plate readers to older FT-IR instruments to further enhance high-throughput analysis.⁴

Q: What are the limitations of standard FT-IR, and how do researchers analyze even smaller particles?

Although FT-IR spectroscopy is commonly used for microplastic analysis, it is not a foolproof technique. Ultimately, the effectiveness of this instrument is dependent on the size of the microplastics it is analyzing. For example, standalone FT-IR spectrometers are effective for larger microplastics but struggle with particles smaller than 10–20 micrometers.^1,3 For these smaller particles, several advanced techniques are used: quantum cascade laser infrared (QCL-IR) spectroscopy, optical photothermal infrared (O-PTIR) spectroscopy, atomic force microscopy-based infrared (AFM-IR) spectroscopy, and Raman spectroscopy.

Q: What are these advanced techniques known for?

Each of these techniques has notable advantages. We note them below:

• QCL-IR Spectroscopy: Known for its rapid analysis speed, making it ideal for time-sensitive studies.¹
• O-PTIR Spectroscopy: This provides submicron spatial resolution, allowing for more precise characterization than traditional methods.¹
• AFM-IR Spectroscopy: This technique bridges the gap between microscopy and spectroscopy, enabling the analysis of plastics at the nanoscale level.¹
• Raman Spectroscopy: Typically used for particles smaller than 10 µm.³ It is non-destructive, but this technique can struggle with very small nanoplastics because of their low Raman cross-section.²

Q: How is surface-enhanced Raman spectroscopy (SERS) advancing the detection of nanoplastics?

SERS is an upgraded version of Raman spectroscopy that uses gold (Au) or silver (Ag) nanoparticles in the 10–100 nm range to amplify signals. Researchers recently developed a cost-effective method using household aluminum foil and copper slug tape to create nanoparticle-on-film (NPoF) substrates.² This innovation allows for the detection of nanoplastics at very low concentrations. One significant benefit of this method is portability; when coupled with handheld Raman instruments, it enables on-site detection in environments like food production facilities or remote field sites, removing the need for laboratory-based analysis.

Q: How do researchers handle the massive amount of data generated by these high-speed instruments?

A single environmental sample can contain millions of particles. To process this, scientists use hyperspectral imaging (HSI), which can measure thousands of spectra in roughly 90 minutes.³ To identify these spectra, researchers rely on open-source software and databases like Open Specy.³ This platform contains over 40,000 reference spectra, allowing for the automated identification of minerals, organic matter, and various synthetic polymers.³

Q: Can you provide an example of how these techniques are applied to track plastics in "pristine" environments?

In a recent study, researchers used µ-FT-IR spectroscopy to investigate microplastic deposits in remote North American snowpacks.³ They discovered that fragment-shaped plastics made of lighter polymers, such as polystyrene, are susceptible to long-range atmospheric transport, reaching even the most isolated mountain peaks.³ Interestingly, they found that snowfall creates a "washout" effect, where the lowest concentrations of MPs are found in fresh snow, while the highest concentrations appear in snow layers formed during long dry periods.³

Q: Are there everyday items being investigated using these spectroscopic tools?

Yes. Researchers recently used automated Raman and SERS to study chewing gum.² They found that gum bases, which often contain non-biodegradable plastics, release micro- and nanoplastics into the oral cavity during chewing.² Because the resulting saliva is swallowed, this research highlights an unrecognized route of human plastic exposure.² This type of research underscores the importance of transparency regarding materials used in consumer products.²

References

1. Workman, Jr., J. Advanced IR Spectroscopy Techniques Revolutionize Micro- and Nanoplastics Research. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/advanced-ir-spectroscopy-techniques-revolutionize-micro--and-nanoplastics-research (accessed 2026-02-13).
2. Chasse, J. Evaluating Micro- and Nanoplastics from Chewing Gum with SERS. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/evaluating-micro--and-nanoplastics-from-chewing-gum-with-sers (accessed 2026-02-13).
3. Wetzel, W. Measuring Microplastics in Remote and Pristine Environments. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/measuring-microplastics-in-remote-and-pristine-environments (accessed 2026-02-13).
4. Wetzel, W. Inside the Laboratory: Portland State University’s Applied Coastal Ecology Laboratory and Oregon State University’s Ecotox and Environmental Stress Laboratory. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/inside-the-laboratory-portland-state-university-s-applied-coastal-ecology-laboratory-and-oregon-state-university-s-ecotox-and-environmental-stress-laboratory (accessed 2026-02-13).