“Three Dimensional Characterization of Pharmaceutical Powders by Scanning White Light Interference Microscopy”

2006:49: Vander Wood, Rose, Miller

Presented at Particles 2006, Medical/Biochemical Diagnostic, Pharmaceutical and Drug Delivery Applications of Particle Technology Conference,May 2006.


Particle dissolution properties depend critically on the three dimensional characteristics of the particle, specifically on the surface area to volume ratio. Traditional methods of characterizing pharmaceutical particles and powders in three dimensions typically rely on estimates derived from measurements made in only one dimension (e.g. light scattering estimates of particulate diameter) or, less frequently, in two dimensions (e.g. particle feret diameters measured from micrographs of the particles in question). Rarely, three dimensional measurements are made using stereographic properties of pairs of two dimensional micrographs or using images of particles tilted through a known angle. These methods are particularly suited to regular particles with a square prism habit, and are labor intensive.

We present here a method of directly characterizing particles in powder samples using scanning white light interference microscopy (SWLIM). This method combines data taken from the two dimensional (x,y) projection of each particle (as in a typical micrograph) with direct measurement of the height (z) of each particle at every pixel encompassed by the projection of each particle. This x,y,z data array is then used to directly calculate the volume and surface area of each particle.

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