Microplastics are present across a range of environments and products, including water, soil, sediments, food, consumer items, and industrial processes. With greater scientific attention and regulatory oversight, laboratories require reliable analytical methods to identify polymer types, measure particle concentrations, and determine particle-size distributions.
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Bruker supports research and testing laboratories worldwide with a broad portfolio of spectroscopic instruments and analytical workflows. Its solutions can be adapted to different objectives, from fast initial screening to the characterization of submicron particles and the generation of results aligned with established standards. This enables users to select an analytical approach suited to their specific requirements.
Bruker’s solutions support dependable assessment of:
- Polymer identity
- Particle counts
- Particle size distributions
- Shape, fiber, and fragment classification
- Weathered and degraded polymers
- Samples containing multiple material types
- Criteria required for regulatory reporting
Microplastics can be detected and analyzed in:
- Drinking, waste, and surface waters
- Marine and ocean samples
- Sediments and soils
- Food and beverages
- Consumer products
- Industrial process streams
- Airborne particle monitoring
Frequently Asked Questions About Microplastics Analysis
This FAQ addresses the practical questions: which technique suits a particular application, which regulatory documents are required, and where the main analytical compromises occur.
Microplastics Basics
What is microplastics analysis?
Microplastics analysis involves detecting, identifying, counting, and characterizing plastic particles under 5 mm in environmental, food, water, and biological samples. A thorough analysis can establish particle abundance, size, shape, and, critically, the type of polymer present.
Where have microplastics been found?
Researchers have detected microplastics in a range of locations and materials, including deep-sea sediments, seawater, Arctic ice, agricultural soils, indoor air, bottled and tap water, and biological tissues such as human lungs, blood, and placentas. Their presence has been documented across marine and freshwater environments, the atmosphere, terrestrial soils, food and drinking water, and biological specimens.
Selecting an Appropriate Microplastics Analysis Method
What are the two main approaches to microplastics analysis?
Microplastic analysis generally follows one of two approaches: mass-based or particle-based analysis. Mass-based methods, including pyrolysis-GC/MS, measure the mass of polymer in a sample. Since these techniques typically destroy samples, they do not provide information about individual particle counts, dimensions, or morphology.
Particle-based methods, such as infrared and Raman microscopy, examine individual particles directly. These techniques can identify polymer composition while also preserving information about particle number, size, and shape.
What are the three primary spectroscopic methods for microplastics analysis?
The three principal techniques are FTIR, IR laser imaging, and Raman microscopy. Though each combines microscopy with spectroscopy to measure the molecular vibration spectrum of a particle, they differ in sample compatibility, spectral coverage, throughput, and spatial resolution.
How do FTIR, IR laser imaging, and Raman microscopy differ?
FTIR microscopy is an established technique for routine microplastic analysis, combining infrared spectroscopy with microscopy to identify polymers while also providing information on particle size and morphology. It is particularly suitable for automated filter analysis and is widely used when dependable, routine particle characterization is needed.
IR laser imaging microscopy (ILIM) also uses infrared spectroscopy but relies on tunable quantum cascade lasers (QCLs) for rapid hyperspectral imaging. Its key advantage is speed: large filter areas can be chemically mapped considerably faster than with conventional FTIR methods, making ILIM especially valuable for high-throughput and full-filter analysis.
Raman microscopy uses visible or near-infrared excitation rather than mid-infrared radiation. Because these wavelengths are shorter, Raman offers higher spatial resolution and is particularly useful for very small particles, including particles around one micrometer and, under appropriate conditions, below this size. It can also provide more information on pigments, fillers, and inorganic components.
Particle Identification and Detection Limits
Why is chemical identification needed in microplastics analysis?
Visual inspection alone cannot distinguish a synthetic polymer particle from a natural particle, such as cellulose or a mineral fragment. This distinction is nevertheless important for understanding particle origin and likely source. Chemical identification through spectroscopy is therefore essential for confirming polymer identity and separating plastic particles from visually similar natural or mineral material.
What determines detection limits?
The detection limits of optical microplastic analysis are governed largely by diffraction, which limits the spatial resolution that a microscope can achieve. The wavelength of the illumination is especially important as a result.
Because mid-infrared radiation has wavelengths in the micrometer range, both FTIR microscopy and QCL-based infrared imaging face inherent resolution constraints when analyzing increasingly small particles.
In routine applications, IR methods can often produce interpretable spectra from particles in the low-micrometer range. However, as particle size approaches approximately 5 µm, reliable identification becomes more difficult. At this scale, individual particles are nearing the practical spatial-resolution limit of the technique.
Raman microscopy can extend analysis to smaller particles because it uses much shorter visible or near-infrared wavelengths. Its higher spatial resolution enables characterization of particles around 1 µm in size and, under suitable conditions, even smaller ones.
What are nanoplastics, and how are they analyzed?
Nanoplastics are generally described as plastic particles smaller than 1 µm. Their analysis is more demanding because the particles approach the resolving capability of conventional optical microscopy: they may even be too small.
Raman microscopy is commonly considered for the characterization of very small particles. When measurements move further into the nanoscale, researchers may need specialized techniques, such as enhanced Raman methods or other analytical approaches designed for nanoscale characterization.
Throughput, Full-Filter Analysis, and Subsampling
What is subsampling in microplastics analysis?
Subsampling involves analyzing only a representative portion of a filter or sample rather than the entire filter. It is often used to reduce measurement time in particle-based spectroscopic workflows, particularly when particle loads are high. However, because particles may be unevenly distributed across a filter, subsampling can introduce uncertainty through spatial bias, handling losses, overcrowding, or analysis of too few particles.
Why can subsampling be risky in microplastics analysis?
Although subsampling can shorten measurement times, the analyzed fraction may not fully represent the entire filter. Edge effects, clustering, uneven particle distribution, and losses during handling can affect reported particle counts, polymer composition, and size distributions.
Bruker’s full-filter IR imaging workflows remove this additional sampling step. ILIM enables analysis of complete 25 mm filters in under 30 minutes, including spectral acquisition and automated data processing, supporting high-throughput evaluation without subsampling.
Sample Preparation and Filter Selection
Why is sample preparation so valuable in microplastics analysis?
Sample preparation is the largest source of variation between laboratories. Inadequate removal of organic and inorganic matrix material can lead to unreliable results and incorrect identifications. Contaminants can be tolerated to some extent and recognized as such by software. However, when contaminants obscure or mask microplastic particles, even software cannot compensate for material that reaches the filter.
What filter should be used for microplastics analysis?
The measurement method determines the appropriate filter. For example, anodisc aluminum oxide filters are commonly used for IR transmission. Silicon membrane filters provide broad mid-infrared spectral access while remaining compatible with Raman.
Gold-coated polycarbonate filters are well-suited for Raman and IR transreflectance measurements. Although PTFE, metal mesh, and nitrocellulose filters have considerable limitations for imaging workflows, they may be appropriate for single-point measurements using ATR.
Can the same filter be used for both IR and Raman analysis?
Silicon membrane filters can be used for both IR transmission and Raman measurements. Gold-coated polycarbonate filters are suitable for Raman and IR transreflectance measurements. Anodisc filters are not suitable for Raman analysis because their surfaces are rough at high magnification and fluoresce under laser excitation.
Data Quality and Classification
How is spectroscopic data evaluated in microplastics analysis?
For imaging-based approaches, automated software such as Bruker’s MPID converts millions of raw spectra into a particle list containing the identity, size, shape, and count of each detected particle. Manual evaluation is impractical at this scale. Automated software can also improve the robustness of classification compared with traditional library matching, particularly for weathered or contaminated samples.
Why does classical library matching fail for environmental microplastics?
Environmental particles often undergo contamination, chemical degradation, and ultraviolet-induced weathering. These changes can alter their spectral signatures, making them differ substantially from clean laboratory reference spectra. As a result, basic library or template matching may not classify them reliably.
In such cases, neural networks trained with spectra from naturally aged and degraded materials can improve identification performance and help maintain classification accuracy under real-world conditions.
What is a confidence score, or HIT score, in microplastics classification?
A confidence score (HIT score) expresses the degree of agreement between a particle’s measured spectral profile and an authenticated reference spectrum associated with a particular polymer class. Analysts can establish a minimum score for accepting an identification, allowing them to retain only results that meet a defined level of confidence.
Adjusting this threshold involves a balance between sensitivity and specificity. Lower thresholds may capture more potential particles but can increase the risk of false classifications, whereas higher thresholds provide more selective identifications while potentially excluding weaker or altered matches.
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Regulatory Requirements and Reporting
Which spectroscopic techniques are recognized for regulatory microplastics analysis?
For drinking-water microplastics analysis, Commission Delegated Decision (EU) 2024/1441 accepts vibrational spectroscopy methods, including μ-FTIR, μ-Raman, and equivalent approaches such as QCL-IR. Laboratories can therefore choose the technique that best matches their needs for particle size, throughput, and level of analytical detail.
Which regulations govern microplastics analysis in water?
Several regulatory and standardization documents are central to water-related microplastics analysis. EU Directive 2020/2184 establishes the EU drinking-water framework, while the Commission Delegated Decision (EU) 2024/1441 defines vibrational spectroscopy methods, including μ-FTIR, μ-Raman, and equivalent approaches including QCL-IR.
ISO 24187:2023 provides general principles for microplastics analysis across environmental matrices, while ISO 16094-2:2025 sets out requirements for vibrational spectroscopy in drinking water and waters with low levels of suspended solids. In addition, ASTM WK87463 is under development as a test method for identifying and quantifying microplastics in water using IR spectroscopy.
Do regulations require FTIR or Raman methods?
No single vibrational spectroscopy technique is mandated by EU Commission Delegated Decision (EU) 2024/1441. Instead, it permits μ-FTIR, μ-Raman, and equivalent methods such as QCL-IR (IR laser imaging) for assessing the composition of microplastic fibers and particles. The most appropriate choice depends on particle size, sample type, throughput requirements, and the analytical criteria being applied.
What is the difference between ISO 24187 and ISO 16094?
ISO 24187:2023 provides principles and broad requirements for microplastics analysis across environmental matrices. By contrast, ISO 16094-2:2025 provides detailed requirements for particle-based analysis using vibrational spectroscopy, particularly for drinking water and waters with low suspended solids content. Laboratories working with these water types should consider the relevant applicable standards.
This information has been sourced, reviewed, and adapted from materials provided by Bruker Optics.
For more information on this source, please visit Bruker Optics.