What was the issue?
As part of its regulatory compliance requirements and quality control of its products, our client, a cosmetics specialist, urgently contacted the FILAB laboratory to demonstrate that the PE it uses is not found in its finished products.
To meet this regulatory and technical challenge, FILAB deployed a proven microplastics detection approach, already validated on many complex matrices in the laboratory. While our methodology is based on rigorous analytical standards, its application is tailored to the client’s real-world needs: here, it takes the form of a custom protocol, optimized for direct analysis on its silicon filters and sized to meet its operational urgency..
The context and the client challenge
The client uses molten Polyethylene (PE) in the formulation of certain products. The main challenge is to demonstrate that this polymer remains perfectly integrated into the product and that there is no presence of microplastics (residual solid Polyethylene particles) in the finished product.
They urgently need to analyze several already prepared filtration samples (cut-off thresholds of 1µm and 5µm to validate the absence or presence of PE microparticles.
For the laboratory to carry out this analysis, the client provided us with specific Silicon filters of 10mm in diameter, ready for analysis.
The technical solution proposed by FILAB
In response to the urgency and the specificity of the matrices, FILAB has implemented a targeted, step-by-step analytical protocol, ensuring maximum efficiency and cost control.
Step 1: Optical screening and molecular characterization (µFTIR)
The first phase of the analysis is based on combining two techniques directly on the surface of the Silicon filters:
1/ Optical microscopy : to locate, count, and map suspicious particles on the filter.
2/ Micro-Fourier Transform Infrared Spectroscopy (µFTIR) : to obtain the chemical signature of particles larger than 50µm (and down to 20-30µm if the matrix allows it). This step makes it possible to reliably distinguish solid polyethylene from any other impurities.
Step 2: Ultra-precise analysis of microparticles (RAMAN spectroscopy)
To ensure complete exhaustiveness and cover the full spectrum of the supplied filters (notably the thresholds at 1µm and 5µm, FILAB systematically carries out a second phase of analysis by RAMAN micro-spectroscopy.
This cutting-edge technology takes over to identify particles of smaller size (less than 20µm), which are inaccessible in conventional infrared analysis.
In addition, it provides the mathematical and physical certainty that no microplastics are present across the entire particle size range required by the regulatory context.
Analyses are carried out on a maximum number of particles per filter. To ensure maximum responsiveness in the face of urgency, investigations are stopped on a sample as soon as the presence of microplastics (polyethylene) is confirmed.
Benefits for the client
Faced with a major regulatory and commercial imperative, the collaboration between FILAB and its client shows that a complex technical constraint can be overcome through a tailored, agile approach.
By combining the complementary strengths of Micro-IRTF (for global screening) and Raman spectroscopy (for detecting the tiniest traces), FILAB provided its client with a complete analytical mapping, carried out directly on its silicon filters. The optimized stop rule (Stop on Positives) and the bundled logistics offer made it possible to reconcile operational urgency with cost control.
Study Conclusion
Thanks to this rigorous protocol, our client secures the compliance of its products, validates control over its Polyethylene formulation processes, and provides indisputable scientific evidence to support its quality requirements. A concrete illustration of FILAB's expertise: turning an urgent technical issue into a calm, lasting compliance solution.
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Frequently asked questions
How can polyethylene particles be identified on industrial filters?
The investigation combines locating the particles on the filter with their chemical identification. In the case studied, FILAB combined optical microscopy, micro-FTIR and Raman microspectroscopy on silicon filters supplied by the client. The objective was to distinguish any solid polyethylene particles from the other residues present.
Why complement micro-FTIR with Raman microspectroscopy when investigating microplastics?
Micro-FTIR chemically characterises particles that are accessible under the method’s conditions. Raman complements the investigation of smaller particles or those requiring a different spectroscopic approach. In this study, the two techniques were combined to adapt the investigation to the size range and characteristics of the filters supplied by the client.
Does a 1 µm cutoff filter guarantee the identification of all particles of this size?
The filter cutoff threshold and the analytical method’s identification capabilities are two different parameters. Interpretation must take into account the particle sizes actually accessible, the matrix, the acquisition conditions and the examination protocol. The presence of a fine filter is therefore not sufficient to conclude that every retained particle has been identified exhaustively.
What does the “Stop on Positives” stopping rule used in this case mean?
The rule provides for stopping investigations on a sample as soon as the presence of polyethylene in particulate form is confirmed. It meets the objective of detecting presence, subject to time and cost constraints. It does not correspond to a complete particle count or an exhaustive measurement of their concentration.
How should a microplastics testing result on a filter be interpreted?
A result relates to the filter analysed, the protocol applied, and the capabilities of the selected techniques. A positive identification documents the presence of the polymer being sought among the particles examined. A non-detection must be considered within the scope of the analysis and does not demonstrate the absolute absence of microplastics throughout the product.