What are microplastics and why to analyze them?
Microplastics are tiny fragments of synthetic polymers, measuring between 1 µm and 5 mm, which result from the degradation of plastic waste or are intentionally manufactured for certain industrial applications (e.g. cosmetics, textiles). They find their way into aquatic and terrestrial ecosystems, posing a major environmental and health problem.
To understand their impact and develop mitigation strategies, it is crucial to be able to detect and analyze them accurately. Various scientific techniques are employed for this purpose.
Microplastics detection techniques
Microplastic concentrations can be evaluated using two primary approaches: methods based on mass and those based on particle count. Mass-based methods determine the total weight of plastic particles and can identify different types of polymers. These techniques often rely on thermoanalytical tools like pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermal desorption GC/MS (TD-GC/MS).
On the other hand, particle-counting methods focus on analyzing individual particles — measuring their number, size, shape, and chemical makeup. This detailed information is essential for toxicology research, as smaller and more numerous particles may present higher health risks.
For particle-number-based analysis, vibrational micro-spectroscopy is the go-to technique, as recognized by ISO standards (ISO 24187:2023, ISO 4484-2:2023, ISO 16094). Raman spectroscopy and Fourier-transform infrared spectroscopy (FTIR) are commonly used to assess the chemical composition, size, shape, and quantity of microplastic particles. Raman spectroscopy, in particular, can detect particles as small as 1 micron, making it especially useful for environmental studies and ecotoxicological assessments
At HORIBA, we offer a range of microscopes tailored to meet your needs for Raman spectroscopy analysis.
Typical workflow for measuring microplastics concentration
Before analyzing the particles, the sample must be prepared to efficiently separate the microplastics from the sample matrix. The choice of preparation method depends on the sample's composition and may include techniques such as density separation, chemical or enzymatic digestion, followed by filtration.
To carry out this filtration, you can use the Micro and nanoplastic kit for filtration to prepare samples for the final stage, liquid phase filtration.
Silicon filters are especially suitable thanks to their smooth, reflective surfaces and consistent pore structure. When particles are placed on these filters and observed using dark-field illumination—which uses a hollow cone of light from the sides—they show up as bright spots against a dark background. Additionally, silicon has a distinct Raman spectrum that doesn’t overlap with those of most polymers, simplifying the interpretation of results.
You can also find silicon filters (Si-Filters-Box for Microplastic analysis) adapted for Raman analysis.
In addition, we offer you microplastic sample holders designed to immobilize filters during analysis.
Following the final stage of sample preparation, the filter usually contains a variety of particles. As a result, precise identification of each particle’s chemical composition is crucial to obtain reliable and meaningful results.
To optimize the analysis of microplastics, we have created the ParticleFinder and IDFinder applications, their advanced tool for automatic particle detection and characterization.
Why use ParticleFinder™?
Our solution automates particle localization and the acquisition of spectra for each particle, making identification and analysis more efficient. It also allows you to select particles for Raman analysis based on size, shape, or statistical criteria, providing maximum flexibility to meet your research needs.
Why use IDFinder™ ?
ID Finder™ is a tool for managing spectral libraries and automatically identifying thousands of spectra. Each spectrum is compared with a dedicated spectral library using the Hit Quality Index (HQI). The component with the highest HQI is recognized as the chemical identity of the particle.
What do we need for method validation?
Method validation is extremely important, as it ensures the reliability of the results obtained. This validation is stipulated in ISO 16094 standards (expected to be published in 2025). To help you comply with this standard, we offer several solutions designed for you.
· Video Raman Matching (VRM): Precision You Can Trust
To ensure the accurate calibration of your instrument, HORIBA offers the Video Raman Matching (VRM) tool.
VRM guarantees that the laser beam is perfectly aligned with the video image of your sample. This ensures accuracy in laser positioning, which is crucial—especially for the precise analysis of the smallest particles.
· References Materials
In order to validate the entire analytical workflow, a set of reference materials should be used. Standards in an easy-to-use tablet format, containing a defined number of polymer particles of specified sizes, are included in the HORIBA package. The irregular shapes of the particles mimic microplastics found in nature. The low concentration of particles in the tablets is specifically designed for the validation of spectroscopy-based particle counting methods. These standards have been successfully tested in interlaboratory studies.
Conclusion
Detecting and analyzing microplastics is essential to understanding their environmental impact and finding solutions to plastic pollution. Among the various techniques available, Raman spectroscopy coupled with the ParticleFinder application stands out for its precision and automation, offering an effective solution for characterizing microplastics in complex environments.
If you'd like to find out more about microplastics analysis, you can contact us right here, stating your requirements, and our experts will be happy to assist you.
For more information about Microplastics: HORIBA - What are Microplastics?
Alina MALTSEVA Market Applications Specialist at HORIBA France
