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

Anna Kukkola; Stefan Krause; Yasmin Yonan; Liam Kelleher; Uwe Schneidewind; Gregory H Sambrook Smith; Holly Nel; Iseult Lynch

doi:10.1016/j.mex.2023.102053

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

MethodsX. 2023 Feb 3:10:102053. doi: 10.1016/j.mex.2023.102053. eCollection 2023.

Authors

Anna Kukkola¹, Stefan Krause^{1

2

3}, Yasmin Yonan¹, Liam Kelleher^{1

2}, Uwe Schneidewind¹, Gregory H Sambrook Smith¹, Holly Nel¹, Iseult Lynch^{1

2}

Affiliations

¹ School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
² Institute for Global Innovation, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
³ LEHNA- Laboratoire d'ecologie des hydrosystemes naturels et anthropises, University of Lyon, Darwin C & Forel, 3-6 Rue Raphaël Dubois, Villeurbanne 69622, France.

Abstract

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 describes 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 microplastic 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 subjectivity in microplastic identification and counting and enhances transparency, repeatability and harmonization within microplastic research community.•Instructions for calibration of detection limits for microplastics on fluorescence microscope systems described•Microplastic identification key developed and tested to reduce false positive detection•Lower subjectivity for microplastic identification obtained using the detection limits & identification key.

Keywords: An easy guide for setting up fluorescence detection limits and a identification key for microplastics identification using Nile Red and fluorescence microscopy.; Detection; Detection limits; Fibres; Fluorescence microscopy; Fragments; Identification; Identification key; Microplastics; Nile Red; Particle counting.