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An Interlaboratory Comparison on the Characterization of a Sub-micrometer Polydisperse Particle Dispersion



Kurt D. Benkstein


The measurement of polydisperse protein aggregates and particles in biotherapeutics remains a challenge. Particles with diameters of ≈ 1 µm and below (sub-micrometer) are particularly challenging to count and size. To assess the current state of these measurements, we have undertaken an interlaboratory comparison on the characterization of a sub-micrometer polydisperse particle (PdP) dispersion composed of five sub-populations of poly(methyl methacrylate) (PMMA) and silica beads. The goal of the study was to characterize particle number concentration as a function of particle size. The study included 20 participating laboratories from industry, academia, and government, and a broad range of counting instruments. The received datasets were organized by instrument class to enable comparison of intralaboratory and interlaboratory performance. The results showed high variability between individual datasets from the different laboratories, with coefficients of variation of ≈ 200 % observed for some instrument classes. Intralaboratory variability was, on average, ≈ 36 % of the interlaboratory variability for a given instrument class and particle size range. Drop-offs at either end of the size range and poor agreement on maximum counts of particle sub- populations were noted. The mean distributions from an instrument class, however, showed the full range of size coverage for that type of instrument. A well-characterized polydisperse sample would facilitate assessing performance capabilities of a given instrument set-up (including hardware, software, and user settings).
Journal of Pharmaceutical Sciences


sub-micrometer, particles, interlaboratory comparison


Benkstein, K. (2022), An Interlaboratory Comparison on the Characterization of a Sub-micrometer Polydisperse Particle Dispersion, Journal of Pharmaceutical Sciences, [online], (Accessed April 12, 2024)
Created March 4, 2022, Updated September 21, 2022