Research on microplastics initially developed in relation to marine pollution, but the range of materials and environments now examined has expanded substantially. Microplastics are now studied in potable water, foodstuffs, atmospheric samples, soils, and biological specimens, reflecting increased concern over exposure, human health, and compliance monitoring.
This broader scope has created greater demand for techniques capable of detecting, enumerating, and characterizing particles in highly diverse matrices.
Which Method Should a Laboratory Choose?
This article outlines how laboratories can select spectroscopic approaches, filter materials, and data-processing procedures for particle-focused microplastic analysis. It considers practical compromises, regulatory relevance, and the limitations of different analytical strategies.
1. What Microplastics Analysis Measures
Microplastics are solid particles composed of synthetic polymers measuring less than 5 mm. They range from fragments large enough to be seen without magnification to particles of approximately 5–10 micrometers, which can only be observed using microscopy.
Within this size spectrum, particle dimensions, form, and polymer composition all carry scientific importance. An analysis should therefore establish not only whether microplastics occur in a sample, but also their abundance, dimensions, shape, and chemical identity.
Microplastics have been reported from surface seawater, deep-sea sediments, Arctic sea ice, farmland soils, indoor air, and components of the human food supply.
Studies also commonly identify contamination in both bottled and municipal tap water, although reported frequencies differ substantially depending on the analytical method, minimum particle size considered, and criteria used for identification.
Several frequently cited surveys found microplastics in as many as 87% of tap-water samples examined globally and in up to 93% of bottled-water brands tested. Particles have also been reported in human lung tissue, blood, and placental samples.
Detection frequencies need to be assessed relative to the methods and detection thresholds used in individual investigations.
Overall, the widespread occurrence of microplastics in the environment is well established and the scale of their environmental distribution is no longer a question.
There are two key types of microplastics: primary and secondary. Primary microplastics are manufactured deliberately, for example as blasting abrasives, plastic pellets, or microbeads used in cosmetic products. They account for a relatively small proportion of the total environmental load.
Secondary microplastics arise when larger plastic items degrade through physical, chemical, and biological processes. These particles constitute most of the microplastic material found in environmental samples.
Tire and road wear particles (TRWP) are widely recognized as an important source of microplastics released into the environment. Tire abrasion is a major contributor to microplastic emissions; in Germany, it has been estimated at roughly 60,000–100,000 tons per year, while peer-reviewed modeling studies have reported comparable estimates of 75,200–98,400 tonnes per year for coarse, non-airborne tire-wear particles.
Other important secondary sources include waste-management emissions, plastic packaging, agricultural plastics, paints, textile laundering, pellet spills, and wear of polymers bound in asphalt.
Nanoplastics, commonly defined as particles below one micrometer, are an emerging concern in toxicology and health-related research. Their small dimensions may allow them to pass through biological barriers, including cell membranes and, potentially, the blood-brain barrier. Because nanoplastic samples are difficult to analyze, they often demand more labor-intensive approaches than standard microplastic studies.
The central analytical difficulty remains consistent across particle sizes: environmental samples are inherently complex mixtures. Synthetic polymer particles occur alongside naturally derived materials, such as mineral grains, cellulose fibers, and biological debris.
Visual examination cannot reliably distinguish a polyethylene particle from a cellulose fiber. Chemical identification of individual particles is therefore essential and underpins any scientifically meaningful 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 macroplastic 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. Mass-Driven Versus Particle-Based Methods
Microplastic analysis can address several different questions, including particle abundance and size distribution, polymer mass concentration, and chemical composition. However, no single approach can provide all of this information simultaneously. The two principal strategies used in microplastic research rest on different principles and yield fundamentally different types of data.
Mass Versus 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-Driven Analysis
Pyrolysis GC/MS (Pyro-GC/MS) is inherently destructive. During analysis, the sample is thermally decomposed, the resulting fragments are separated by gas chromatography, and polymers are identified and quantified through mass spectrometry. The result is a quantitative profile showing which polymers occur in the sample and their concentrations by mass.
Pyro-GC/MS is therefore well-suited to questions concerning total polymer burden. Its principal drawback is that it does not retain information on particle size. In practical terms, a single large plastic fragment can produce the same result as a collection of smaller particles with an equivalent combined mass.
Once pyrolysis has occurred, no intact particles remain. Information regarding whether particles are fibers or fragments, and about their size distribution, morphology, and particle counts is lost. The analyzed sample also cannot be stored for later review or reanalysis.
For this reason, mass-based techniques cannot supply particle-level measures for regulatory or biological applications, although they remain valuable for providing complementary information on polymer mass.
One way to introduce limited size information into mass-based analyses is to separate particles into size classes before chemical measurement. This is commonly achieved through sieving, filtration cascades, or sequential separation procedures, frequently combined with density separation. Samples can then be divided into defined size categories before analysis by Pyro-GC/MS or related approaches, such as TED-GC/MS.
Commonly reported categories include coarse material greater than 300 or 500 micrometers, intermediate material between 100 and 500 micrometers, and fine material below 100 micrometers. Exact boundaries depend on the sample matrix, required sensitivity, and aims of the study.
Although this approach does not retain the identity of individual particles, it enables polymer mass to be linked to size ranges that are more directly relevant to exposure modeling, particle transport, and risk assessment.
Size fractionation nevertheless introduces additional uncertainty. Particles may be lost during sieving or filtration through adhesion to apparatus, blockage, or incomplete transfer between processing stages. Fine particles and fibers are particularly susceptible to these losses.
Physical handling can also fragment or deform particles, altering the apparent size distribution. For these reasons, size-fractionated mass-based approaches are not commonly used in microplastic research, largely because the field prioritizes identification at the particle level.
The attached article focuses on particle-based microplastic analysis and examines the metrics used in regulatory and standardization settings, together with the data generated by particle-focused evaluation techniques. In practice, particle-based and mass-based methods are frequently applied together, depending on the study objectives and regulatory requirements.
This information has been sourced, reviewed, and adapted from materials provided by Bruker Optics.
For more information on this source, please visit Bruker Optics.