As part of their comparative study, the researchers at the University of Bayreuth and at the Helgoland site of the AWI examined two sets of samples with both evaluation algorithms. The quantity and size of the microplastic particles and the proportions of various polymers were measured. One sample set contained ten water samples from the Upper and Middle Weser, the other sample set ten water samples originating from the Lower/Outer Weser and the Jade Bay.
"We deliberately chose to conduct our comparison of the two analytical tools with sample sets from the environment, because all environmentally relevant types, shapes and sizes of polymers are encountered here. In addition, the very small microplastic particles are particularly common in the environment, and the smaller the particles are, the higher their hazard potential. This makes it all the more important to evaluate the latest methods such as micro-FTIR spectroscopy and automated analysis of FTIR data sets, which are suitable for investigations of these particles," says Prof. Dr. Christian Laforsch, spokesman of the SFB "Microplastics" at the University of Bayreuth and corresponding co-author of the study.
For the new study, the researchers in Bayreuth and Helgoland compared the results obtained in parallel with the two analysis tools. Overall, the results are largely consistent. But there are also deviations: Especially in the range of particles smaller than 50 micrometers, there are different results, because here the algorithms can also make wrong decisions as a result of poorer FTIR spectra quality. "Our study shows that further comparative research is needed so that microplastic particles of all sizes can be identified without error using automated methods. Results obtained so far on the contamination of the environment by microplastics should definitely be viewed with a certain degree of skepticism, especially with regard to smaller size classes. Furthermore, our study proves that we obtain good and robust data when we finally subject the data obtained with the analysis tools to a critical review," says co-author Dr. Martin Löder from the University of Bayreuth. "However, with all the techniques and methods currently in use, it ultimately remains unclear how well the results obtained in the process reflect the actual microplastic loads in the environment. Even if we use modern, technically advanced investigation methods, the question of how many and which microplastic particles actually pollute the environment cannot yet be answered conclusively. Particularly in the case of the very small particles, we are still at the very beginning here, which makes further research efforts all the more important," emphasizes Prof. Dr. Christian Laforsch.