Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance

Abstract In the European Union, nanomaterials are regulated through different pieces of sectoral legislation. This legislation often requires risk assessments and thus reliable characterization data, for which regulatory guidance generally recommend electron microscopy. The guidance provides best pr...

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Main Authors: Charlotte Wouters, Vikram Kestens, Eveline Verleysen, Jan Mast
Format: Article
Language:English
Published: Nature Portfolio 2025-04-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-92266-4
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author Charlotte Wouters
Vikram Kestens
Eveline Verleysen
Jan Mast
author_facet Charlotte Wouters
Vikram Kestens
Eveline Verleysen
Jan Mast
author_sort Charlotte Wouters
collection DOAJ
description Abstract In the European Union, nanomaterials are regulated through different pieces of sectoral legislation. This legislation often requires risk assessments and thus reliable characterization data, for which regulatory guidance generally recommend electron microscopy. The guidance provides best practices for measurements but lacks requirements on how many particles to measure. Using transmission electron microscopy data of nanomaterials, a strategy based on repeated subsampling is proposed to establish, for different particle size and shape measurands, mathematical relationships between particle count and precision, and subsequently to determine the minimum particle count. Our results confirm that the minimum particle count generally depends on the width of the size and shape distributions and that the median of the distribution can be determined with the highest precision compared to other percentiles. Upon combining the precision uncertainty related to particle number with uncertainties from other sources, such as sample preparation, calibration and trueness, we reach an optimal particle count above which additional particle measurements only yield negligible improvements to the combined measurement uncertainty. Our findings offer an experimental approach for determining the minimum particle count to measure particle size and shape by electron microscopy. It enables efficient analyses and facilitates compliance with legislation addressing nanomaterials across various application domains.
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spelling doaj-art-4f32208f8e3c4adbb18c3b8b7d1dbb2c2025-08-20T02:28:05ZengNature PortfolioScientific Reports2045-23222025-04-0115111310.1038/s41598-025-92266-4Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidanceCharlotte Wouters0Vikram Kestens1Eveline Verleysen2Jan Mast3Trace Elements and NanomaterialsEuropean Commission, Joint Research Centre (JRC)Trace Elements and NanomaterialsTrace Elements and NanomaterialsAbstract In the European Union, nanomaterials are regulated through different pieces of sectoral legislation. This legislation often requires risk assessments and thus reliable characterization data, for which regulatory guidance generally recommend electron microscopy. The guidance provides best practices for measurements but lacks requirements on how many particles to measure. Using transmission electron microscopy data of nanomaterials, a strategy based on repeated subsampling is proposed to establish, for different particle size and shape measurands, mathematical relationships between particle count and precision, and subsequently to determine the minimum particle count. Our results confirm that the minimum particle count generally depends on the width of the size and shape distributions and that the median of the distribution can be determined with the highest precision compared to other percentiles. Upon combining the precision uncertainty related to particle number with uncertainties from other sources, such as sample preparation, calibration and trueness, we reach an optimal particle count above which additional particle measurements only yield negligible improvements to the combined measurement uncertainty. Our findings offer an experimental approach for determining the minimum particle count to measure particle size and shape by electron microscopy. It enables efficient analyses and facilitates compliance with legislation addressing nanomaterials across various application domains.https://doi.org/10.1038/s41598-025-92266-4Electron microscopyNanomaterialPrecisionParticle countRegulatory guidanceParticle size
spellingShingle Charlotte Wouters
Vikram Kestens
Eveline Verleysen
Jan Mast
Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
Scientific Reports
Electron microscopy
Nanomaterial
Precision
Particle count
Regulatory guidance
Particle size
title Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
title_full Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
title_fullStr Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
title_full_unstemmed Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
title_short Assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
title_sort assessing particle count in electron microscopy measurements of nanomaterials to support regulatory guidance
topic Electron microscopy
Nanomaterial
Precision
Particle count
Regulatory guidance
Particle size
url https://doi.org/10.1038/s41598-025-92266-4
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AT evelineverleysen assessingparticlecountinelectronmicroscopymeasurementsofnanomaterialstosupportregulatoryguidance
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