TUM-ParticleTyper: A detection and quantification tool for automated analysis of (Microplastic) particles and fibers

PLoS One. 2020 Jun 23;15(6):e0234766. doi: 10.1371/journal.pone.0234766. eCollection 2020.

Abstract

TUM-ParticleTyper is a novel program for the automated detection, quantification and morphological characterization of fragments, including particles and fibers, in images from optical, fluorescence and electron microscopy (SEM). It can be used to automatically select targets for subsequent chemical analysis, e.g., Raman microscopy, or any other single particle identification method. The program was specifically developed and validated for the analysis of microplastic particles on gold coated polycarbonate filters. Our method development was supported by the design of a filter holder that minimizes filter roughness and facilitates enhanced focusing for better images and Raman measurements. The TUM-ParticleTyper software is tunable to the user's specific sample demands and can extract the morphological characteristics of detected objects (coordinates, Feret's diameter min / max, area and shape). Results are saved in csv-format and contours of detected objects are displayed as an overlay on the original image. Additionally, the program can stitch a set of images to create a full image out of several smaller ones. An additional useful feature is the inclusion of a statistical process to calculate the minimum number of particles that must be chemically identified to be representative of all particles localized on the substrate. The program performance was evaluated on genuine microplastic samples. The TUM-ParticleTyper software localizes particles using an adaptive threshold with results comparable to the "gold standard" method (manual localization by an expert) and surpasses the commonly used Otsu thresholding by doubling the rate of true positive localizations. This enables the analysis of a statistically significant number of particles on the filter selected by random sampling, measured via single point approach. This extreme reduction in measurement points was validated by comparison to chemical imaging, applying both procedures to the same area at comparable processing times. The single point approach was both faster and more accurate proving the applicability of the presented program.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Automation
  • Image Processing, Computer-Assisted
  • Microplastics / analysis*
  • Microscopy*

Substances

  • Microplastics

Grants and funding

Funding by the Bayerische Forschungsstiftung (https://www.forschungsstiftung.de/) for the Project MiPaq “Microparticles in the aquatic environment and in foodstuffs” are biodegradable polymers a conceivable solution to the “microplastic problem”?, AZ-1258-16 is gratefully acknowledged. Funding by the German Federal Ministry of Education and Research https://www.bmbf.de/ for the Project MiWa – Microplastic in the water cycle, 02WRS1378C is gratefully acknowledged. Furthermore, this work was supported by the German Research Foundation (DFG, https://www.dfg.de/) and the Technical University of Munich, within the funding program Open Ac-cess Publishing. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript