There is a gamut of particle size distribution measurement techniques each with established history and advantages. The killer word in particle size distribution ids the last one (distribution) and measurement of broad distributions is the bane of all sizing techniques. After a very short introduction to ‘how much sample should we measure to describe the distribution’, we’ll be running through the background of some of the more popular techniques (sieves, sedimentation, electrical-sensing zone) and will emphasize the popular light scattering techniques of laser diffraction and dynamic light scattering. As anaside we’ll be mentioning Small-angle X-ray scattering (SAXS).
We’ll look at counting techniques especially those in the nanotechnology (nanotracking analysis (NTA), resonant mass measurement (RMM)) and regulatory (obscuration counting) arena. In line with the statement in USP <766> Optical Microscopy, “For irregularly shaped particles, characterization of particle size must also include information on particle shape’, we will look at the benefits of high speed image analysis where statistically valid numbers of particles can be counted and measured for both size and shape distribution. We’ll point out 2 international (ISO & ASTM) standards that provide an overview to available methods.