Pharmaceutical characterization of commercially available intravenous fat emulsions: estimation of average particle size, size distribution and surface potential using photon correlation spectroscopy.

Particle profiles such as the average diameter, size distribution and dispersion, as well as the zeta potential, of commercially available intravenous fat emulsions of high-calorie nutrient fluids (6 products) and drug carriers (4 products) were examined using photon correlation spectroscopy (dynamic light scattering). Wide variations were observed in number-weighted (dn), weight-weighted (dw) and z-average diameters, and dw/dn ratios as a measure of polydispersity. Average size is not sufficient for the pharmaceutical characterization of particles and the determination of size distribution or dw/dn value is essential for more precise information. Although measuring the zeta potential of fat emulsions is of considerable value in estimating their stability on long-term storage, a medium which accurately reflects the environment of the droplets in the system of interest should be chosen when diluting the emulsion.