Size analysis of metered suspension pressurized aerosols with the Quantimet 720

A method is described for particle sizing of pressurized metered suspension aerosols by collection in a settling drum followed by microscopic evaluation of the slides with a Quantimet 720 automatic image analyser. The method gives satisfactory representation of the distribution of particles settling to the drum base, and demonstrates the excellent stability and reproducibility between and within aerosol packs for two widely used inhalation products. There is much drug deposition of somewhat finer size distribution on the wall of the drum than on the drum base. In spite of this wall loss, the method gives only slightly higher results for the weight and number mean diameters, than when both wall and base distributions are considered. The Quantimet was found to be suitable for particle sizing salbutamol used in preparing aerosol products.