A critical analysis on the limits and possibilities of the μ-Raman as a routine method for microplastics determination in drinking water

This paper critically discusses the results of an experimental activity aimed at investigating the possibilities of μ-Raman analysis for routine monitoring of microplastics in drinking water in view of the application of the guidelines proposed by the European Union. Automatization in the water analysis reduces the required time and influence of the operator on the results. It is of utmost importance in the context of routine monitoring for the quality assessment. Automatized protocols selected from the state-of-the-art were implemented in a real monitoring campaign on a drinking water treatment plant from central Italy treating surface water. Technical limits were found in the performance of the automated image analysis algorithm and the motorized stage precision. Such limits might increase the lowest limit automatically analyzable by μ-Raman from 1 μm to 5 μm, whereas the assessment of MPs > 20 μm was not impaired. Regarding results reporting, it was highlighted the need of standardization in polymers grouping in major clusters. Regardless, the automation in the size range 20-500 μm was shown to be satisfactory and upgradable by few software adjustments. The overall analysis time was calculated to be about 4-5 h. The results also showed a MPs scarce contamination (<2MPs/L), coherently with the findings of previous studies.