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.
Highlights
Microplastic (MP) may be formed from plastic over time by, fragmentations under the influence of UV light and mechanical abrasion, as well as oxidation and biological breakdown [1]
The smoothness of the filter is of high importance, as any subsequent measurement, be it Fourier-transform infrared spectroscopy (FTIR) or confocal Raman microspectroscopy, will depend on a flat surface to enable optimal focus on the particles [11, 12]
This is especially true if automated routines are used, where particles are first identified by acquiring images for a morphological assessment, including the determination of the particle centers for the subsequent measurement
Summary
Microplastic (MP) may be formed from plastic over time by, fragmentations under the influence of UV light and mechanical abrasion, as well as oxidation and biological breakdown [1]. The smoothness of the filter is of high importance, as any subsequent measurement, be it Fourier-transform infrared spectroscopy (FTIR) or confocal Raman microspectroscopy, will depend on a flat surface to enable optimal focus on the particles [11, 12] This is especially true if automated routines are used, where particles are first identified by acquiring images for a morphological assessment, including the determination of the particle centers for the subsequent measurement. A third path is to apply an automatic thresholding routine, which can be overruled by the user to “make the segmentation look good” This is a valid approach, used in most commercial software, as the current gold standard for the identification of particles in images is still the human operator. The initial focus was on microscopy images taken with darkfield illumination, and it was subsequently adapted to the analysis of SEM and fluorescence images
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
