Influence of cohesive properties of micronized drug powders on particle size analysis

Particle size analysis results with respect to micronized, mean particle size below 10 microns, furosemide, chloramphenicol palmitate and acetaminophen particles are dealt with in this paper. Special consideration was given to the effect of the agglomeration of particles on data generated by three size measurement techniques. The physicochemical basis for preparing sufficiently well dispersed and stable suspensions for analysis by employing mechanical methods of pretreatment are shown. Furthermore, methods to determine the state of dispersion and methods to assess the individual particle size before size analysis are described. An attempt was also made to establish the statistical confidence that can be assigned to a particular instrument and the confidence level that may be placed on comparative data obtained with the different particle size analysers. Results especially showed the impact of the agglomeration of very small furosemide particles, mean size 3 microns, on particle size analysis and the importance of controlling the cohesive properties of this drug. To overcome the problems associated with agglomeration more attention must be paid to the physical properties of the drug substance. Combining particle size analysis with bulk density, surface area and microscopical studies also helped to identify potential problems.