The present invention relates generally to the field of plastic microparticles. In particular, the present invention relates to the detection of plastic microparticles in a water-based sample. An embodiment of the present invention relates to a process for detecting and characterizing plastic microparticles in a water-based sample comprising the analysis of the sample by spectral flow cytometry. In accordance with the present invention, the process described herein may comprise the processing of the recorded flow cytometry data by a machine learning algorithm that can distinguish and categorize each particle based on its unique spectrum to characterize, for example, the plastic microparticles.