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Abstract
The accurate characterization of the particle size and shape distribution (PSSD) of ensembles of crystals is essential for effective design, modeling, and control of crystallization processes. Various techniques for measuring PSSDs have been introduced at both laboratory and pilot scales. Despite the wide range of techniques available for the measurement of PSSDs, there is a noted gap in the literature concerning a comparative analysis of these methods when characterizing one, two, and three-dimensional particle size (and shape) distributions (PS(S)D) of population of crystals. To this end, five commercial and two bespoke techniques were used to characterize nine particle ensembles, with some obtained with supplier-specified properties, and others specifically prepared for this study. The evaluated instruments include the Mettler Toledo's FBRM, BlazeMetrics' probe, Mettler Toledo's EasyViewer, Malvern's Laser Diffraction, and Malvern's Morphologi; in addition to a stereoscopic imaging device (DISCO) and a confocal microscopy device (Petroscope). Test samples include small, medium, and large spherical glass beads with known size ranges; small and large sodium chloride cubes obtained through sieving; two populations of needle-like D-mannitol crystals; plate-like adipic acid crystals; and agglomerated L-Glutamic acid crystals. The results show that online devices generally disagree with each other, with offline devices, and with independent size references such as sieve fractions. For equant particles, offline devices exhibit good agreement with each other and independent size references. However, discrepancies arise for non-equant crystals (i.e. needles and plates). Only the Morphologi, DISCO, and Petroscope offer 2D characterization (measuring length and width), while only the non-commercial bespoke techniques, i.e. DISCO and Petroscope, provide 3D characterization (measuring length, width, and thickness). Comparing the measured multidimensional PSSDs reveal small differences between the two bespoke devices. The outcomes from this study will inform practitioners on the strengths and limitations of PS(S)D characterization techniques and in turn their selection for specific applications.
Supplementary materials
Title
Supplementary Information for “Is There a ‘Right’ Particle Size and Shape Measurement Tool?: A Comparative Study of Seven Online and Offline Devices on Nine Different Particle Populations”
Description
Supplementary Information to this article includes descriptions of the measurement techniques used; equations used to convert between distribution types; additional results showing the effect of stirring rate and suspension density on in-situ measurements; a comparison of the 1D distributions of length, width, and aspect ratio provided by the EasyViewer with the DISCO, Petroscope, and Morphologi; a comparison of the distributions obtained using out focus particles, and all particles provided by the EasyViewer; a comparison of the DISCO, Petroscope, and Morphologi on the small fraction of non-agglomerated BLGA crystals; a discussion of the effect of using different length estimation algorithms with the DISCO, alternative representations (non-cumulative, number-weighted, quantiles) of the PS(S)Ds reported; and figures comparing all measurements obtained with a single device to asses distinguishability of the different populations when using a specific device.
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