Particle size distributions by transmission electron microscopy: an interlaboratory comparison case study

Abstract

This paper reports an interlaboratory comparison that evaluated a protocol for measuring and analysing the particle size distribution of discrete, metallic, spheroidal nanoparticles using transmission electron microscopy (TEM). The study was focused on automated image capture and automated particle analysis. NIST RM8012 gold nanoparticles (30 nm nominal diameter) were measured for area-equivalent diameter distributions by eight laboratories. Statistical analysis was used to (1) assess the data quality without using size distribution reference models, (2) determine reference model parameters for different size distribution reference models and non-linear regression fitting methods and (3) assess the measurement uncertainty of a size distribution parameter by using its coefficient of variation. The interlaboratory area-equivalent diameter mean, 27.6 nm ± 2.4 nm (computed based on a normal distribution), was quite similar to the area-equivalent diameter, 27.6 nm, assigned to NIST RM8012. The lognormal reference model was the preferred choice for these particle size distributions as, for all laboratories, its parameters had lower relative standard errors (RSEs) than the other size distribution reference models tested (normal, Weibull and Rosin–Rammler–Bennett). The RSEs for the fitted standard deviations were two orders of magnitude higher than those for the fitted means, suggesting that most of the parameter estimate errors were associated with estimating the breadth of the distributions. The coefficients of variation for the interlaboratory statistics also confirmed the lognormal reference model as the preferred choice. From quasi-linear plots, the typical range for good fits between the model and cumulative number-based distributions was 1.9 fitted standard deviations less than the mean to 2.3 fitted standard deviations above the mean. Automated image capture, automated particle analysis and statistical evaluation of the data and fitting coefficients provide a framework for assessing nanoparticle size distributions using TEM for image acquisition.

Post hoc Interlaboratory Comparison of Single Particle ICP-MS Size Measurements of NIST Gold Nanoparticle Reference Materials

“…Recently, an interlaboratory study using NIST RM 8012 for particle size distribution evaluation by transmission electron microscopy (TEM) was performed. 37 In the present study we mainly used TEM and scanning electron microscopy (SEM) results provided in the NIST Report of Investigation, because scientists conducting spICP-MS analysis most frequently compare their results to the reported SEM and TEM sizes and often use TEM sizes for spICP-MS calibration.…”

Size and shape distributions of primary crystallites in titania aggregates

“…The coefficients of variation for the size descriptors of the full ILC are significantly larger than those reported by Rice for a gold nanoparticle certified reference material [15]. Since a key objective of this certified reference material is to provide a known standard for size, its coefficient of variation for the size descriptor should be relatively small.…”

“…Classical analysis methods are available for particle size and particle size uncertainties [11-14]. A semi-automated image analysis method has reported size distribution statistics from an interlaboratory comparison (ILC) [15] of gold reference material samples [9]. Here, a more realistic, commercial sample of nanoscale titanium dioxide in an aggregated/agglomerated state is analyzed using manual image analysis methods.…”

The Impact of Sampling Medium and Environment on Particle Morphology

“…Indeed, freezing and thawing cycles of collected particles have been shown to cause severe particle agglomeration due to water uptake [24]. Finally, even for perfect samples, the human factor may contribute to a bias during image analysis through particle discrimination based on size and shape, as discussed previously [28][29][30].…”