Analysis of Microplastics in Drinking Water Using µ-FTIR Vibrational Spectroscopy
With the entry into force of Royal Decree 3/2023 , new technical and health criteria for the quality, control and supply of drinking water were established. The new legislation replaced Royal Decree 1798/2010, which regulated the exploitation and marketing of natural mineral waters and spring waters bottled for human consumption. One of the new features of Royal Decree 3 is the inclusion of microplastics in the watch list in ANNEX IV. Point 4 states that they will be included on the list when the European Commission adopts a standardized method for measuring microplastics in drinking water (Provision 628 of Official Spanish Gazette (BOE) No. 9 of 2023).
On 11 March 2024, the European Parliament and the European Commission approved a new measure supplementing Directive (EU) 2020/2184, specifically Article 13, by adopting a methodology for measuring microplastics in water intended for human consumption. An annex to this directive providing details on the analysis methodology was also approved.
Analysis Methodology
This method is based on passing a minimum volume of 1,000 litres of water through several cascade filters. The method is limited to particles with dimensions between 20 µm and 5 mm and fibres with a length between 20 µm and 15 mm. The particles and fibres must subsequently be analysed using vibrational micro-spectroscopy methods such as µ-FTIR, µ-Raman or equivalent variations such as (QCL)-IR. The results obtained during the analysis allow for categorization of particles by their shape, size, composition and polymer type. The identification of particles and fibres from acquired spectra must be performed by comparison with spectra of known polymers contained in a spectral library. The library used for identification should contain spectra of priority polymers and also include examples of proteins, minerals and natural polymers such as cellulose that might commonly be present in water intended for human consumption.
The document also outlines how to verify the methodology for analysing microplastics in drinking water.
It is necessary to verify the recovery of material when filtering water. To do this, a known quantity of standard reference microplastics such as polyethylene (PE) and polyethylene terephthalate (PET) can be used to spike the sample. The quantity recovered by the filters can then be verified and the analysis procedure is considered acceptable if the recovery rate is within the range of 100% to +/- 40%.
At least 20% of the total filter surface must be analysed while following an appropriate strategy to maintain a representative sample. It is also very important to analyse a minimum of ten procedural blanks to calculate the mean and standard deviation of contamination, which will be used to control variations during analyses. Finally, the identification of microplastics requires the use of libraries of known polymer spectra. To ensure positive identification of polymers, experimental verifications must be carried out to evaluate the acceptance criteria of spectrum matching. These measures ensure that the analysis process is reliable and reproducible, and also allow the identification of possible sources of error or contamination in the results.
How Can AIMPLAS Help You?
At AIMPLAS, we work on the analysis of microplastics in drinking water using µ-FTIR to stay ahead of upcoming legislation and assist companies that need to comply with this new regulation. Our validated method is based on our library of standard reference microplastics.
When analysing filters using µ-FTIR, the area of the filter containing the sample is scanned. It is recommended that the filter is completely taut, smooth and even, for which filter holders like the one shown in panel (a) of Figure 1 can be used. The scan image, known as a chemical image [panel (b)], is formed by the accumulation of spectra taken during the scan. The image is then processed (panel c) to show the detected particles more clearly. Finally, the spectra corresponding to each particle are selected and compared with the spectral library (panel d).
Analysis of a drinking water sample using µ-FTIR. Filter holder with a sample to be analysed (a). Chemical image obtained (b). Processed image (c). Comparison of spectra obtained with the spectral library (d).
If you need to analyse microplastics, do not hesitate to contact our laboratory.
