title: Particle shape effects on subvisible particle sizing measurements.
abstract: Particle analysis tools for the subvisible (<100 μm) size range, such as light obscuration, flow imaging (FI), and electrical sensing zone (ESZ), often produce results that do not agree with one another, despite their general agreement when characterizing polystyrene latex spheres of different sizes. To include the effect of shape in comparison studies, we have used the methods of photolithography to create rods and disks. Although the rods are highly monodisperse, the instruments produce broadened peaks and report mean size parameters that are different for different instruments. We have fabricated a microfluidic device that simultaneously performs ESZ and FI measurements on each particle to elucidate the causes of discrepancies and broadening. Alignment of the rods with flow causes an oversizing by FI and undersizing by ESZ. FI also oversizes rods because of the incorrect edge definition that results from diffraction and imperfect focus. We present an improved correction algorithm for this effect that reduces discrepancies for rod-shaped particles. Tumbling of particles is observed in the microfluidic ESZ/FI and results in particle oversizing and breadth of size distribution for the monodisperse rods.
authors.affiliation: Bioprocess Measurements Group, National Institute of Standards and Technology, Gaithersburg, Maryland.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Cavicchi
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Carrier
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Cohen
authors.forename: Shir
authors.initials: S
authors.lastname: Boger
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Montgomery
authors.forename: Zhishang
authors.initials: Z
authors.lastname: Hu
authors.forename: Dean C
authors.initials: DC
authors.lastname: Ripple
mesh_terms: D000465:Algorithms; D004867:Equipment Design; D056656:Lab-On-A-Chip Devices; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013499:Surface Properties; D013678:Technology, Pharmaceutical / Q000295:instrumentation / Q000379:methods*
chemical_list: D004364:Pharmaceutical Preparations
keywords: electrical sensing zone; flow imaging; image analysis; light obscuration; light scattering (static); microscopy; particle sizing; physical characterization