SUBMICROMETER PARTICLE SIZING BY MULTIANGLE LIGHT-SCATTERING FOLLOWING FRACTIONATION

The acid test for any particle sizing technique is its ability to dete rmine the differential number fraction size distribution of a simple, well-defined sample. The very best characterized polystyrene latex sph ere standards have been measured extensively using transmission electr on microscope (TEM) images of a large sub-population of such samples o r by means of the electrostatic classification method as refined at th e National Institute of Standards and Technology. The great success, i n the past decade, of on-line multiangle light scattering (MALS) detec tion combined with size exclusion chromatography for the measurement o f polymer mass and size distributions suggested, in the early 1990s, t hat a similar attack for particle characterization might prove useful as well. At that time, fractionation of particles was achievable by ca pillary hydrodynamic chromatography (CHDF) and field flow fractionatio n (FFF) methods. The latter has proven most useful when combined with MALS to provide accurate differential number fraction size distributio ns for a broad range of particle classes. The MALS/FFF combination pro vides unique advantages and precision relative to FFF, photon correlat ion spectroscopy, and CHDF techniques used alone. For many classes of particles, resolution of the MALS/FFF combination far exceeds that of TEM measurements. (C) 1998 Academic Press.