The early stages of microplastics research initially focused largely on marine contamination, but the field now covers a much wider range of applications. Investigations increasingly include drinking water, food, air, soil, and biological materials because of concerns about environmental exposure, human health, and regulatory compliance.
This broader scope has created demand for analytical workflows that can consistently detect, identify, count, and describe particles in highly different sample matrices.
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Which Analytical Approach Best Fits a Particular Laboratory?
This article explains how laboratories can choose spectroscopic methods, filter materials, and data-processing workflows for particle-based microplastic analysis. It considers practical compromises between speed, sensitivity, regulatory expectations, and the technical limitations associated with each approach.
#1 What Does Microplastic Analysis Measure?
Microplastics are solid particles made of polymers and smaller than 5 mm. They include relatively large fragments that may be visible without magnification as well as particles measuring approximately five to 10 micrometers that require microscopy for detection.
Within this broad size range, particle dimensions, morphology, and polymer composition all provide important information. A meaningful analysis must not only determine whether microplastics are present, but also establish the number of particles, their size and shape, and the materials from which they are made.
Microplastics have been reported in surface seawater, deep-ocean sediments, Arctic ice, agricultural land, indoor air, food chains, and bottled and tap waters. However, the reported frequency of detection differs substantially depending on the method used, the smallest particle size included, and the criteria applied for chemical identification.
Several widely referenced surveys found microplastics in as many as 87% of tap-water samples examined worldwide and in up to 93% of bottled-water brands tested. Microplastics have additionally been reported in human lung tissue, blood, and placental tissue. Such detection rates must be considered alongside the analytical sensitivity, size thresholds, and identification procedures used in the individual studies.
These studies have proven that microplastic contamination in the environment is no longer a question of whether, but rather of how much.
Many of these studies distinguish between primary and secondary microplastics. Primary microplastics are manufactured intentionally for specific uses, for example, abrasive blasting media, plastic resin pellets, and cosmetic microbeads. These materials account for a smaller proportion of the total environmental burden.
Secondary microplastics form when larger plastic items deteriorate through physical wear, chemical reactions, and biological activity. They represent the predominant form of microplastics found in many environmental samples.
Tire and road wear particles (TRWP) are widely recognized as an important source of environmental microplastic emissions. In Germany, tire abrasion has been estimated at approximately 60,000–100,000 t/a. Peer-reviewed modeling studies have reported similar estimates of 75,200–98,400 t/a for coarse, non-airborne tire-wear particles.
Other significant secondary sources include plastic packaging and waste-management activities, agricultural films and other agricultural plastics, paint deterioration, textile laundering, losses of plastic pellets, and the abrasion of asphalt-associated polymers.
Nanoplastics, generally defined as particles smaller than 1 µm, have become an increasing focus of toxicological and health-related research. Their small dimensions may allow them to pass through biological barriers, including cell membranes and potentially the blood–brain barrier.
However, because they are difficult to isolate and characterize, nanoplastic analysis commonly requires more time and specialized procedures than conventional microplastics testing.
Despite the differences in size and source, the central analytical problem remains consistent: environmental samples are chemically and physically complex. Synthetic particles occur alongside minerals, cellulose fibers, biological matter, and other naturally occurring materials.
Visual inspection cannot reliably distinguish a polyethylene fragment from a cellulose fiber. Chemical identification of individual particles is therefore essential and provides the basis for interpreting the result.
What Are Microplastics?
Source: Bruker Optics
| Contaminant Classification |
Physical Size Boundaries |
Primary Environmental Genesis |
Predominant Analytical Challenges |
Key Representative Examples |
| Primary Microplastics |
5 µm to 5 mm |
Intentionally manufactured for specific industrial functions or consumer product formulations |
Locally concentrated near industrial sites; requires differentiation from secondary background fragments |
Cosmetic microbeads, raw manufacturing resin pellets (nurdles), abrasive blast media |
| Secondary Microplastics |
5 µm to 5 mm |
Progressive physical, chemical, and biological degradation of larger macro-plastic waste |
Extreme structural heterogeneity; often heavily weathered, bio-fouled, or embedded in matrix residues |
Tire and road wear particles (TRWP), synthetic textile wash fibers, fragmented agricultural films |
| Nanoplastics |
Sub-micron (<1 µm/<1000 nm) |
Advanced fragmentation and continuous degradation of microplastic particles |
Sits below the optical diffraction limit of standard mid-infrared microspectroscopy |
Sub-micron polymer colloids, weathered synthetic dusts capable of cellular translocation |
| Natural/Inorganic Background Matrix |
Highly variable (<0.1 µm to
>5 mm) |
Naturally occurring biotic and abiotic environmental components |
Inflicts heavy spectral interference; can completely mimic plastic particles under visual inspection |
Cellulose (cotton/wood fibers), chitin, mineral shards (silica/quartz), biofilms |
#2 How Should Users Choose Between Mass-Based and Particle-Based Methods?
Microplastics studies may seek information about particle number, size distribution, polymer mass, or chemical composition. However, no single analytical technique provides all of these measurements at the same time; the two principal approaches are based on different measurement principles and produce different types of results.
Mass and Particle Metrics
Source: Bruker Optics
| Metric Category |
Primary Technique |
Data Output |
Core Advantages |
Critical Limitations |
| Mass-Driven |
Pyrolysis GC/MS (Pyro-GC/MS); TED-GC/MS |
Total polymer mass concentration profile (mg/kg or µg/L) |
Quantifies total polymer burden; high matrix tolerance |
Destructive; entirely blind to particle count, size distribution, and morphology. Pre-separation via sifting introduces uncertainty in particle loss |
| Particle-Driven |
FTIR microscopy, quantum cascade laser (QCL) IR, Raman microscopy |
Spatially resolved particle counts, discrete sizing, morphology metrics, and chemical typing |
Matches toxicological exposure models; non-destructive nature permits archival storage and retrospective audit |
Requires rigorous sample preparation to mitigate spectral interference from co-extracted matrices |
Mass-Based Analysis
Pyrolysis GC/MS (Pyro-GC/MS) is a destructive technique. During analysis, the sample is thermally decomposed, the resulting compounds are separated by gas chromatography, and mass spectrometry is used to identify and quantify the polymers. The resulting report describes which polymer types are present and the concentration of each polymer by mass.
This makes Pyro-GC/MS useful for determining the overall polymer burden in a sample. Its principal limitation is that the technique does not distinguish how that mass is distributed among particles. A single large fragment and many smaller particles can generate the same result if their combined polymer mass is equivalent.
Once pyrolysis is complete, the original particles no longer exist. Particle number, size distribution, morphology, and the distinction between fibers and fragments are lost. The processed material also cannot be archived for later reanalysis.
For regulatory and biological investigations that increasingly require particle-level information, mass-based analysis cannot supply all relevant metrics. It nevertheless remains valuable as a complementary method for measuring the total mass of specific polymers.
Some size information can be introduced before mass analysis through size fractionation. This may involve sieving, staged filtration, sequential separation, or density-based separation to divide the sample into size categories before Pyro-GC/MS or related methods such as TED-GC/MS are applied.
Common categories include coarse fractions above 500 or 300 µm, intermediate fractions from 100–500 µm, and fine fractions below 100 µm. The exact boundaries vary according to the sample matrix, method sensitivity, and goals of the study.
Although this approach does not retain the identity of each individual particle, it allows polymer mass to be associated with size ranges that may be useful for transport studies, exposure modeling, and risk assessments.
Size fractionation also creates additional uncertainty. Particles may be lost during sieving or filtration because they adhere to equipment, become trapped in blocked filters, or are not fully transferred between processing stages. Fine particles and fibers are particularly susceptible to these losses.
Mechanical manipulation can also break particles apart or alter their shape, thereby changing the apparent size distribution. Consequently, size-fractionated mass analysis is not commonly the primary approach in studies that require particle-specific information. Most microplastics investigations focus instead on identifying and characterizing individual particles.
In practice, mass-based and particle-based methods may be combined when the research question or regulatory setting calls for complementary information. The attached guide provides more information about particle-based microplastics analysis, including the metrics used in regulatory and standardization frameworks and the information generated by particle-resolved methods.
This information has been sourced, reviewed, and adapted from materials provided by Bruker Optics.
For more information on this source, please visit Bruker Optics.