Particle Size Measurements in Aerosols
Pharmaceutical aerosols comprise a wide range of drug products which all are dispersed as droplets (wet aerosol) or particles (dry aerosol) in a gas for application. Hence, the device being used for dispersion plays a very important role as it impacts the dispersion efficiency and significantly influences the resulting aerosol particle size. For an aerosol’s therapeutic effect it is important how the particles behave in the gas they are dispersed in, i.e. how they distribute and deposit. Therefore, aerodynamic particle size is important in addition to a geometrical particle size—unlike many other formulations where only geometrical particle size is looked at. The chapter defines the differences in particle sizes and gives an overview of measurement techniques to determine aerodynamic particle size as well as other sizing techniques in use for aerosol particle sizing. Pharmacopoeial requirements are summarized and physiological implications as well as ideas to closer mimic the in vivo situation are discussed.
KeywordsAccessories to mimic in vivo situation Aerodynamic particle size Cascade impaction Geometric particle size Particle deposition mechanisms Pharmacopoeial requirements Sample dispersion
- Byron PR, Wei X, Delvadia RR, Longest PW (2013) Standardizing in vitro test methods to support aerosol drug evaluation in the clinic. Respir Drug Deliv 1:85–92Google Scholar
- de Backer J (2012) Novel imaging in assessing small airway disease and therapy. In: Proceedings of DDL 23. Edinburgh, ScotlandGoogle Scholar
- Dekati (2010) Dekati ELPI: electrical low pressure impactor. TampereGoogle Scholar
- Hinds WC (1999) Aerosol technology—properties, behavior and measurement of airborne particles. John Wiley & SonsGoogle Scholar
- Kippax P, Fracassi J (2003) Particle size characterisation in nasal sprays and aerosols. LabPlus InternationalGoogle Scholar