How to Test Microplastics: Characterisation Techniques

Microplastics analysis has become one of the most pressing challenges in environmental science. From ocean sediments to drinking water, agricultural soils to human tissues, plastic fragments smaller than 5 mm are now detected virtually everywhere researchers look [1]. Recent studies have identified microplastics in human blood and brain samples tested, raising urgent questions about exposure pathways and health impacts [2].

A CSIRO report, released in 2020, found the wastewater treatment plant at Malabar in Sydney discharged an estimated 5.4bn to 120bn microplastic particles into the ocean each day [3]. This finding exemplifies a global challenge: microplastics are everywhere and accurately characterising them requires sophisticated analytical techniques.

This article examines the analytical techniques that enable researchers to identify, quantify, and characterise microplastics from spectroscopic methods to electron microscopy.

Understanding Microplastics: Definition and Significance

Microplastics are plastic particles smaller than 5 mm, while nanoplastics are typically defined as particles below 1 μm in size. As particle size decreases, their behaviour and potential impact change significantly: smaller particles have greater surface area-to-volume ratios, enhanced mobility in water and air, increased likelihood of biological uptake across cell membranes and epithelial barriers, and potentially higher reactivity and toxicity. These particles originate from a range of sources, including synthetic textile fibres released during washing, tyre wear debris, fragmentation of larger plastic waste, and historically from microbeads used in personal care products prior to regulatory bans. Micro- and nanoplastics have now been detected across multiple environments—including water, soil, air and sediment—as well as in biological samples, highlighting their widespread distribution. Together, their small size, chemical complexity, heterogeneity, and low environmental concentrations establish micro- and nanoplastics as a significant and evolving analytical challenge [4].

Why Microplastics Characterisation Matters

Characterisation of micro- and nanoplastics provides critical information including polymer type, particle size distribution, shape and morphology, and concentration. This data underpins robust risk assessment, as different polymers possess distinct chemical compositions, densities, additives, and degradation behaviours that influence their persistence and potential toxicity. Size is particularly important, with smaller particles more likely to cross biological barriers and interact at the cellular level, leading to size-dependent biological effects. Similarly, particle shape—whether fibres, fragments, films or spheres—can affect transport, bioavailability and ecological interactions. Together, these parameters determine environmental fate and biological impact, highlighting the urgent need for standardised, reproducible analytical methods to support regulatory frameworks and meaningful comparison of data across studies [5].

The Analytical Challenge: Sample Complexity

Detecting and characterising microplastics presents significant analytical challenges. Environmental and biological samples are typically complex matrices—such as wastewater, sediment, soil or tissue—requiring extensive sample preparation to isolate plastic particles without altering their properties. Contamination during sampling and processing is a major concern, as airborne fibres and laboratory materials can easily introduce false positives [6]. No single analytical technique can provide complete characterisation across polymer type, size, morphology and concentration, often necessitating complementary methods. The size range of interest spans several orders of magnitude—from millimetre-scale fragments down to nanometre-sized particles—further complicating detection. In addition, environmental weathering and degradation can modify polymer chemistry, surface properties and fragmentation behaviour, making identification and interpretation even more complex [7].

Sample Preparation Considerations

Preparing microplastic samples for testing involves a multi-step process designed to remove organic and inorganic debris to isolate plastic particles for analysis. The process varies slightly depending on the sample matrix (water, sediment, or biota) but generally includes sampling, digestion, separation, and identification. The main challenge is that there seems to be a lack of standardised methods currently on the analysis required for microplastic clean-up and compliance. Dr Nina Wootton of the University of Adelaide has developed the best practice Microplastics Field Manual, which includes processing and laboratory procedures to facilitate reliable data comparisons across regions [8]. The Nano Microplastics Research Consortium [9] based at Flinders University in South Australia is helping to define best analysis practices, while collecting data on the environmental occurrence of nano and microplastics to assess their effect on human health.

Spectroscopic Techniques for Polymer Identification

Spectroscopic techniques are the primary, non-destructive methods used to identify, count and size microplastics found in water, sediment, biosolids, and biota samples. Eurofins Environment testing Australia was the first accredited microplastics testing facility in Australia in 2023. The most common polymers tested at the lab include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polyurethane (PU), polytetrafluoroethylene (PTFE) and polyamide (PA) [10].

Fourier Transform Infrared (FTIR) Spectroscopy

Fourier Transform Infrared (FTIR) spectroscopy is a non-destructive analytical technique widely used to analyse particle sizes down to 5-10 µm and determine the chemical composition of microplastics. It identifies a broad range of polymer types by measuring their characteristic molecular bond vibrations. Because different chemical bonds and functional groups produce distinct spectral patterns, FTIR provides a unique chemical “fingerprint” that distinguishes synthetic polymers from organic and inorganic materials, enabling qualitative identification of microplastic particles.

Conventional FTIR analysis can be limited by slow, labour-intensive manual sampling and a relatively higher size detection limit (typically >10–20 µm) compared with Raman spectroscopy. Analysis of weathered, degraded, or mixed-polymer particles can also be challenging. Careful sample preparation is essential to minimise spectral interference from residual organic matter and by the presence of water [11].

More recently, FTIR imaging techniques have been developed that combine spectroscopy with imaging for chemical mapping. These approaches enable higher-throughput analysis, allowing automated identification, quantification, and spatial mapping of microplastics in complex samples across a wider size range.

Raman Spectroscopy and Microscopy

Raman spectroscopy can be used to identify the polymer type. It is based on the interaction of a light with chemical bonds within a material. Raman spectroscopy works by shining a monochromatic laser light onto a sample and measuring the scattered light. Most of the light is scattered elastically (Rayleigh scattering) with no change in energy, but a very small fraction is scattered inelastically—this is the Raman effect. Photons either gain or lose energy depending on the vibrational modes of the molecules and these energy shifts produce a spectrum that reflects the specific molecular bonds and chemical structure of the material. Each type of polymer or chemical compound generates a characteristic “fingerprint” spectrum, which can be compared to reference spectra to identify the material [13]. By combining Raman spectroscopy optical microscopy (e.g MDRS), users can simultaneously determine the polymer type and measure the size of individual particles down to approximately 1 µm. It provides a more comprehensive understanding of the microplastics present, including their potential sources and environmental fate. What’s more, Raman spectroscopy supports measurement in water [12].

Microscopy Techniques for Physical Characterisation

Microscopy is widely used to identify and quantify microplastics based on particle size, shape, and visual appearance. However, when performed manually (such as visual identification using stereomicroscopes or staining with dyes like Nile Red), it can be subjective, time-consuming, and prone to user bias, with natural or non-plastic materials sometimes misclassified as microplastics. Chemical characterisation can help to confirm and identify the type of polymers present in the sample [14].

Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Spectroscopy (EDS)

SEM-EDS allows users to quantify and identify microplastics while also detecting trace contaminants on particle surfaces, all with minimal sample preparation. The Thermo Scientific Phenom ProX Desktop SEM is ideal providing fast, easy to use, high-resolution imaging combined with fully integrated chemical analysis for microplastic research.

Using back-scattered electron (BSE) imaging, dense particles like metals can be easily distinguished and excluded, while secondary electron (SE) imaging can highlight non-conductive plastics and surface morphology. Combining these detectors saves time by focusing analysis only on relevant particles. Integrated EDS enables elemental characterisation, providing insight into additives or surface pollutants [15].

The Phenom XL can accommodate multiple large samples up to 100 mm x 100 mm and SEM automations to handle repetitive tasks using custom-made scripts. Chloroscan was developed to detect PVC microparticles in mussel samples. While EDS cannot directly identify PVC, the high chlorine content in PVC provides a reliable marker. The script analyses a back-scattered electron (BSE) image, automatically identifies particles, and performs EDS point analysis on each. It then calculates the chlorine content at each point and flags particles likely to be PVC. Capable of analysing thousands of particles in a short time, Chloroscan is an invaluable tool for large-scale particle studies, enabling rapid and consistent detection across complex samples [16].

Particle Size and Shape Analysis

Particle size and shape analysis are essential for understanding the behaviour and impact of microplastics. Size influences transport, bioavailability, and potential toxicity, with smaller particles posing greater biological risk. Shape—such as fibres, fragments, or beads—can indicate likely sources and degradation pathways. Automated imaging techniques provide high-throughput, reproducible measurements of size and morphology, reducing user bias and improving the reliability of microplastic characterisation.

Laser Diffraction Particle Size Analysis

Laser diffraction, as used by the Mastersizer 3000+, provides rapid, reproducible measurement of particle size distributions across a very broad size range, from sub-micron to millimetre scale.

Laser diffraction measures particle size distributions by measuring the angular variation in intensity of light scattered as a laser beam passes through a sample. Large particles scatter light at small angles and small particles scatter light at large angles. The angular scattering intensity data is then analysed to calculate the size, reported as a volume equivalent sphere diameter, of the particles using the Mie theory.

Mastersizer 3000+  measures thousands to millions of particles in seconds, delivering statistically robust data representative of the whole sample. It requires minimal sample preparation, works with both dry powders and wet dispersions, and is highly repeatable, making it ideal for routine screening, quality control, and bulk microplastic analysis. User-guided software, with built in features like Data Quality Guidance and SOP Architect, enable automatic measurement setup, method development and live data monitoring. By accurately quantifying size distribution, laser diffraction helps researchers understand particle behaviour, transport, settling, and potential environmental or biological impact.

Dynamic Light Scattering (DLS)

Dynamic Light Scattering (DLS) is a well-known, non-invasive measurement for the characterisation of nano- and micro-scale particles in a liquid dispersion. The technique measures the time-dependent fluctuations in the intensity of scattered light that occur due to the random movement of the particles or molecules undergoing Brownian motion. The velocity of this Brownian motion is measured and is called the translational diffusion coefficient (D) which can be converted into a hydrodynamic diameter (DH) using the Stokes-Einstein equation.

The Zetasizer is the preferred DLS system used for micro- and nano-plastics analysis because it is a fast, high-sensitivity method to determine particle size distribution, aggregation state, and surface charge (via zeta potential) in liquid dispersions. It is particularly effective for particles in the submicron range (0.3 nm to 10 µm) and, using Non-Invasive Backscatter (NIBS) technology, can measure complex, dilute, or opaque environmental samples, such as those with UV-degraded particles or additives. The latest Zetasizer Ultra systems use Multi Angle DLS (MADLS) to deliver higher resolution size (angular-independent) and concentration analysis, while Adaptive Correlation automatically identifies and filters out transient artifacts (like dust or large contaminants) from the data, resulting in more accurate and reproducible size distributions, even in complex samples. The Zetasizer also uses Electrophoretic Light Scattering (ELS) to measure zeta potential, which is critical for understanding the stability of microplastics in water and their interactions with other contaminants or biological organisms [18].

Nanoparticle Tracking Analysis (NTA)

NTA is a powerful characterisation technique that complements DLS and is particularly valuable for analysing polydisperse nanosized particles. NTA has been used to characterise the formation of degraded plastic nanoparticles from a polystyrene (PS) disposable coffee cup lid. The NTA results show a change in the size profile but more importantly an increase in the concentration over time [20].

Unlike DLS, which is intensity based and measures the average diffusion of a bulk sample, NTA is number based and tracks each particle individually. This provides a higher-resolution size distribution, essential for identifying different populations in polydisperse, environmental samples.

The NanoSight Pro, using Nanoparticle Tracking Analysis (NTA), is the most widely cited NTA solution in peer-reviewed biomaterials research. Light scatter mode measures individual nanoparticles in real time – assessing size distribution, particle concentration, and aggregation state. Fluorescence mode can be used to detect and analyse labelled subpopulations, track specific biomarkers, or quantify labelled cargo. Machine learning–based particle identification using the NS Xplorer software ensures accurate tracking and removes user subjectivity, so every result is consistent and highly reproducible [20].

Automated Imaging Particle Analysis

Non-destructive chemical techniques such as Raman spectroscopy are increasingly used to confirm polymer identity. Identification can be further enhanced through automation using Morphologically-Directed Raman Spectroscopy (MDRS), which combines automated particle imaging with targeted Raman analysis to deliver more accurate, reproducible, and efficient microplastic characterisation [12].

The Morphologi 4-ID delivers detailed component-specific morphological descriptions of particulate mixtures through Morphologically-Directed Raman Spectroscopy (MDRS). It combines automated particle imaging with Raman spectroscopy in a single, integrated platform. Complimentary particle size, shape and chemical identification information is provided for thousands of individual microplastic particles, with the classification of these particles enabling sample data to be easily compared in numerous ways, such as by plastic type or by morphology [12].

Applications: Microplastics Analysis in Environmental Matrices

Microplastics analysis is essential for understanding the impact of plastic pollution. Although they are ubiquitous on our planet, their effect on human health and ecosystems remain poorly understood. Our continued reliance on plastics means microplastic concentrations are likely to increase in the years ahead. This makes research essential to understand the effects that exposure to microplastics will have on our lives and to inform strategies for mitigation and regulation [18].

Water and Wastewater Analysis

Microplastics in water raise concerns for both drinking supplies and marine life. Analysis typically involves filtering a known volume of water to collect particles, followed by optical microscopy for sizing and Raman spectroscopy for polymer identification. Techniques such as laser diffraction can also support size analysis in suspension. Together, these methods provide insight into the origin, behaviour, and potential environmental impact of microplastics [18].

Soil and Sediment Analysis

Microplastics are increasingly found in soil and sediment, accumulating from agricultural runoff, wastewater, and from the breakdown of larger plastic debris. They can affect soil structure, water retention and microbial activity, potentially affecting plant growth and ecosystem health. Analysis typically involves separating plastics from a soil sample via separation and filtration, followed by optical or electron microscopy for particle sizing and imaging, and vibrational spectroscopy (FTIR or Raman) for polymer identification and quantification. These techniques together help reveal the types, sizes, and potential environmental impacts of microplastics in terrestrial and aquatic sediments [22].

Biological Samples

Microplastics can accumulate in biological samples such as tissues and blood, raising concerns about their potential impact on human health. In February 2025, researchers detected microplastics in the brains of human cadavers, with individuals who had dementia showing up to ten times more plastic than those without the condition. Studying their links to chronic diseases is complex – plastics vary widely in size, shape, and chemical composition, and may trigger different biological effects in different people. They can absorb toxins, carry heavy metals, and interact with hormones, while nanoplastics are small enough to cross cellular membranes and accumulate within cells and cause inflammation. To better understand toxicity thresholds, scientists are using vascular organoids—lab-grown 3D structures that mimic human blood vessels—to study how much microplastic exposure the body can tolerate [23]. These findings underscore the urgent need to deepen our understanding of microplastics and to develop safer alternatives that protect both human health and the environment.

Cosmetics/ Glitter

Much like microbeads, which were banned from cosmetics and personal care products in many states across Australia from 2022, there is now a call to ban other plastics. Glitter is an innocuous example  – normally made of plastic – and is found everywhere like cards, crafts, cosmetics, ornaments and clothes to just name a few. Yet it has been found to accumulate in soil and waterways, which harms marine organisms and ultimately can end up in our food. The particle size distribution of glitter can be quickly and reproducibly measured using the Mastersizer 3000+ with the Aero S dry dispersion accessory [21]. Measurements can contribute to a greater understanding of their impact and lead to new biodegradable alternatives.

Challenges and Future Directions

In Australia, key challenges in microplastic research include detecting particles across a wide size range (from millimetres to nanometres), analysing complex environmental matrices, avoiding contamination during sampling and processing, and accurately identifying weathered or mixed-polymer particles. There is also limited standardisation in sampling and analysis methods, making comparisons between studies difficult. Greater emphasis on environmental monitoring, risk assessment, and policy-informed strategies will support efforts to mitigate microplastic pollution in Australia’s waterways, soils, and marine environments.

ATA Scientific can offer a range of automated, analytical techniques (e.g., combining spectroscopy, microscopy, and chemical imaging) to improve detection, quantification, and source tracking.

Our UK supplier, Malvern Panalytical, is part of the Netherlands-based MOMENTUM project [17], which brings together expertise in microplastics research and recently published a roadmap to reduce health impacts from microplastic exposure. As part of this initiative, the project has explored creating “microplastic passports” for toxicology samples. Malvern Panalytical contributes by using the Mastersizer 3000+ for rapid particle size analysis, the Epsilon 4 XRF for elemental composition, and the Morphologi 4-ID with Morphologically-Directed Raman Spectroscopy (MDRS) for combined particle size, shape, and chemical identification. Together, these techniques enhance understanding of how microplastics in water affect human and environmental health.

For those interested in exploring microplastic analysis with these instruments, our team of specialists at ATA Scientific are available to assist.

The Analytical Toolkit: A Practical Summary

This toolkit enables comprehensive microplastic analysis—from bulk quantification to detailed particle-level chemical and morphological characterisation—supporting environmental research studies.

ATA Scientific’s Commitment to Environmental Research

ATA Scientific is committed to supporting environmental research on microplastics by providing advanced analytical instruments and expertise that enable accurate detection, characterisation, and quantification of plastic particles in complex samples. Through partnerships with researchers ATA Scientific facilitates studies that improve understanding of microplastic sources, composition, and environmental impacts, helping drive solutions to reduce pollution and protect human and ecosystem health.