Easy and accessible way to calibrate a fluorescence microscope and to create a microplastic identification key

We present here a technique for setting up detection limits on any fluorescent microscope in conjunction with the fluorophore Nile Red for microplastic identification. Our method also de-scribes a rigorous morphology-specific identification key for microplastics to reduce subjectivity between researchers. The detection limits were established for nine common polymer types and five natural substrates which could result in false-positive signals when using Nile Red for mi-croplastic identification. This method was then applied to real freshwater samples and identified particles were validated with micro-FTIR or Raman spectroscopy. This approach may reduce sub-jectivity in microplastic identification and counting and enhances transparency, repeatability and harmonization within microplastic research community.center dot Instructions for calibration of detection limits for microplastics on fluorescence microscope systems described center dot Microplastic identification key developed and tested to reduce false positive detection center dot Lower subjectivity for microplastic identification obtained using the detection limits & iden-tification key

Automated summary

This article presents a technique for setting up detection limits on any fluorescent microscope using the fluorophore Nile Red for microplastic identification. It also introduces a morphology-specific identification key to reduce subjectivity among researchers. The method establishes detection limits for nine common polymer types and five natural substrates that could result in false-positive signals when using Nile Red. It is applied to real freshwater samples and validated by micro-FTIR or Raman spectroscopy, reducing subjectivity in microplastic identification and enhancing transparency, repeatability, and harmonization in the research community.