Influence of humidity on the electrostatic charge and aerosol performance of dry powder inhaler carrier based systems

Paul M. Young, Adrian Sung, Daniela Traini, Philip Kwok, Herbert Chiou, Hak-Kim Chan

Research output: Contribution to journalArticlepeer-review

99 Citations (Scopus)


To investigate the influence of storage relative humidity (RH) on the aerosolisation efficiency and tribo-electrification of carrier based dry powder inhaler (DPI) formulations using the next generation impactor (NGI) in vitro methodology and the electrostatic low pressure impactor (ELPI). Micronised salbutamol (d 0.5 1.48 ± 0.03 μm) was blended with 63–90 μm sieve fractioned α-lactose monohydrate carrier and stored at a range of humidities (0–84% RH). The aerosolisation efficiency after storage for 24 h periods was investigated using the NGI. The same experiment was conducted using the ELPI, with corona charger switched off, to measure the net charge vs. mass deposition profile. Significant variations in the aerosolisation efficiency of the formulation were observed with respect to storage RH. In general, the fine particle fraction aerosol performance measured by NGI and ELPI (fraction with mass median aerodynamic diameter <4.46 and 4.04 μm, respectively) followed a positive parabola with aerosol performance increasing over the range 0–60% RH before decreasing >60% RH. Analysis of the ELPI charge data suggested that the micronised salbutamol sulphate had an electronegative charge when aerosolised from lactose based carriers, which was most electronegative at low RH. Increased storage RH resulted in a reduction in net charge to mass ratio with the greatest reduction at RH >60%. The aerosol performance of this binary system is dependent on both electrostatic and capillary forces. The use of the ELPI allows a degree of insight into how these forces affect formulation performances after storage at different RH.
Original languageEnglish
Pages (from-to)963-970
Number of pages8
JournalPharmaceutical Research
Issue number5
Publication statusPublished - May 2007
Externally publishedYes


  • aerosol
  • DPI
  • dry powder inhaler
  • electrostatics
  • ELPI
  • humidity
  • inhalation


Dive into the research topics of 'Influence of humidity on the electrostatic charge and aerosol performance of dry powder inhaler carrier based systems'. Together they form a unique fingerprint.

Cite this