The Dilution of Monodisperse Suspensions for Aerosolization

The use of aerosols produced by atomization of suspensions of monodisperse spheres, such as polystyrene latex spheres, is common for testing and calibrating air sampling equipment and studying aerosol behavior. The dilution required to yield a desired fraction of single particles has been customarily determined by trial. In this discussion a formula is developed for estimating the dilution required to produce a given singlet ratio (ratio of single particles to all particles), it being assumed that the atomizer used produces a droplet distribution which is log-normal. It is found that the dilution is proportional to the cube of the droplet distribution median diameter and inversely proportional to the cube of the monodisperse particle diameter. The fraction of droplets which do not contain particles is also calculated; this is found to depend only on the desired singlet ratio and the geometric standard deviation of the droplet distribution.