Particle Size During Nebulization

Marcel Dekker, Inc. 270 Madison Avenue. New York, New York 10016 

Glass slide captures particles Aerosol collection 

As stated above, nebulizer function may be dependent on flow through 

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During nebulization from airjet nebulizers, cooling of the reservoir solution occurs which, together with vapor loss, results in concentration of the dmg solution. This in turn produces an aerosol output in which the drag concentration increases with time. Concentration of the dmg solution in the reservoir can lead to drug recrystallization with subsequent blockage within the device or variation in aerosol particle size. 

A compromise between the concentration of the precursor solution, the flow rate of air fed to the nebulizer, and the orifice of the nebulizer needs to be met in order to obtain crystalline materials with nanometric particle size. A further optimization parameter is the humidity degree of the air fed to the nebulizer, which needs also to be controlled as it ensures a constant precursor concentration during nebulization thus providing constant production rate and particle size [71],... 

The latter approach—completely drying the aerosol— while valid, is diffi-cnlt to perform experimentally (29). The low solids content of pharmaceutical nebulizer solutions results in dry aerosols that are too fine for reliable enough measurements to be made to allow back calculation with any accuracy. For example a typical nebulizer droplet distribution with a mass median diameter of 3 pm generated from a 0.1% drug solution would result in a dry particle distribution with a mass median diameter of 0.1 pm. Obtaining size distribution data with any reasonable resolution at this size is very problematic. A further issue is that the solids content of the original droplets must be known in order to perform the calculation, and this can vary considerably during the course of nebulization. This technique has therefore not been used extensively. 

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