Analysis of microplastics

Most of the plastics we currently use in our daily lives are not biodegradable, which means they last over time when unintentionally released into the environment.

These materials are considered microplastics when they are made of petroleum- or bio-based polymers, are solid, are less than 5 mm in size, are not water soluble and have low degradability.

Microplastics are also used widely and directly in products such as cosmetics, plastic paints and abrasive and industrial cleaning products, though such use is not currently standardized.

Legislation designed to regulate microplastics throughout their life cycle in the value chain of plastic materials is therefore being drafted.

As part of the definition of “microplastics”, which include plastics less than 5 mm in size, standard UNE-CEN ISO/TR 21960 further defines microplastics measuring between 1 and 5 mm in size as “large microplastics”, and microplastics under 1 µm as nanoplastics. This wide range of particle sizes creates several limitations on the different analytical identification techniques available when the aim is to analyse individual particles while bearing in mind their size and morphology. The resolution of the techniques themselves sometimes makes it impossible to distinguish particles smaller than a specific size and this can be particularly difficult when working with nanoplastics and microplastics smaller than 5 to 20 µm. In these cases, mass detection and identification techniques are generally used because they make it possible to analyse smaller fractions of particles without obtaining information on each individual particle.

Analysis techniques

Análisis de microplásticos

In AIMPLAS, in addition to keeping up with the legislative changes that are taking place in relation to microplastics, we work with different techniques for their analysis that include the following ones::


FTIR spectroscopy and IR microscopy

Compared with other vibrational spectroscopy methods, infrared spectroscopy (IR) is easy to apply in experiments and is therefore routinely used to analyse plastics and determine their structure. The sample is subject to electromagnetic radiation in the infrared region of the spectrum. The wavelengths at which absorption takes place are recorded and make up what is known as the sample’s infrared spectrum.

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Differential scanning calorimetry (DSC)

Thermal analysis is defined as the set of techniques used to measure a material’s physical or chemical properties as the sample changes temperature.

Of the different techniques included within the concept of thermal analysis, differential scanning calorimetry (DSC) can be considered the fundamental technique for thermal characterization of polymer systems. In this technique, the test sample is subject to a temperature-controlled programme and the difference is measured between the energy absorbed or released by the sample compared to the reference sample.

Análisis termogravimétrico

Thermogravimetric analysis (TGA)

This test measures the variation of mass of a sample material as temperature rises at constant speed. Weight loss takes place when the volatile compounds absorbed by the sample evaporate at low temperatures and due to polymer degradation at high temperatures.

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Chromatographic techniques

Among the different characterization techniques, it is important to distinguish between direct techniques (infrared and ultraviolet-visible spectroscopy) and indirect techniques (chromatography). Direct techniques allow for quick analysis of the sample and make it unnecessary to perform the preliminary separation stage. However, very low proportions of additives cannot be analysed using these techniques because interference from signals from the polymer matrix can mask the signals of these additives.

After the preliminary separation stage, chromatographic techniques make it possible to separate complex mixtures, as well as identify and quantify the components of these mixtures, even in samples with a low concentration.

Técnicas cromatográficas
Microscopía SEM EDX

Optical and electronic microscopy (SEM/EDX)

Microscopy is the set of techniques and methods used to view objects of study whose small size means they are outside the resolution of the human eye (100 mm). Microscopy techniques generally involve diffraction, reflection or refraction of the electromagnetic radiation interacting with the specimen. The range of the spectrum of interacting light determines the type of microscopy: optical microscopy involves visible light and photons, whereas electron microscopy makes use of electrons. The shorter the wavelength of light, the higher the resolution of the technique.

Methodologies for the extraction of microplastics

AIMPLAS has developed methods for extracting microplastics from different types of samples. These methods include filtration processes, separation by density and digestion of organic matter.
We make all these tools and knowledge on microplastics available to our clients. Please contact us to find out more.

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Neus Soriano

Characterisation Laboratory