Electrostatic Properties of Particles for Inhalation

  • Martin Rowland

Student thesis: Doctoral ThesisPhD


Dry powder inhalers (DPIs) and pressurised metered dose inhalers (pMDIs) aredevices used to deliver therapeutic agents to the lungs. Typically, inhaled activepharmaceutical ingredients (APIs) are electrically resistive materials and are prone toaccumulating electrostatic charge. The build-up of charge on inhaled therapeutics hastraditionally been viewed as a nuisance as it may result in problems such as weighingerrors, agglomeration, adhesion to surfaces and poor flow. Energetic processing stepssuch as micronisation, blending, blister/capsule filling as well as fluidisation of the dosewill result in a large number of particulate collisions which can result in charge transfer.Charge present on aerosol particles may also affect the in vivo performance by alteringthe inhaler delivery efficiency and promoting electrostatic precipitation within the lung.This study aimed to develop and assess repeatable and reliable methods of performingelectrostatic measurements of particles for inhalation and to understand therelationship of charge with environmental relative humidity.A powder ladle was constructed to perform net charge measurements of inhalationgrades of lactose and used to assess the extent of triboelectrification during low shearturbula blending. Results demonstrated the importance of the method of addition usedto transfer a sample to a net charge measurement device.The electrical properties of DPI formulations were investigated using a Charge DecayTime Analyser. It was determined that both API concentration and relative humidityplay an essential role in governing the extent to which a DPI formulation can becomeelectrostatically charged and the subsequent rate of charge decay.Finally, the bipolar Next Generation Impactor (bp-NGI) was developed and assessedas a tool to measure the bipolar charge to mass ratios of therapeutic aerosol particlesin order to address the unmet need of combining a bipolar charge measurementsystem with an industry standard aerosol particle size classifier.
Date of Award1 Oct 2014
Original languageEnglish
Awarding Institution
  • University of Bath
SupervisorRobert Price (Supervisor)

Cite this