Aerosol Science 35 (2004) 755–764 www.elsevier.com/locate/jaerosci Electrostatic charge characterization of pharmaceutical aerosols using electrical low-pressure impaction (ELPI) William Glover ∗ , Hak-Kim Chan Faculty of Pharmacy, Pharmacy University of Sydney, Building A15, NSW Sydney 2006, Australia Received 18 September 2003; received in revised form 22 December 2003; accepted 22 December 2003 Abstract A novel method for characterizing the electrostatic charge in pharmaceutical aerosols was developed. Electri- cal low-pressure impaction (ELPI) was modied and optimized to allow the measurement of aerosol particles from metered dose inhalers (MDIs) for anti-asthmatic drugs. Two commonly used MDIs, Ventolin TM and Flixotide TM , were investigated for the charging properties of their emitted aerosols. Ventolin TM aerosol was found negatively charged, whilst Flixotide TM aerosol was bipolarly charged, containing both positive and neg- ative charged particles. The electrostatic charge measurements for both MDIs were reproducible with %CV ranging from 3.3% to 12.5% for 10 actuations from each of the inhalers. In addition, chemical assay was undertaken to obtain mass distributions of the aerosol collected inside the ELPI. Both MDIs showed that only a small amount of the drug was recovered from the submicron size range where a large amount of charge was present (negative charge for Ventolin TM and positive for Flixotide TM ). For the Flixotide TM , the majority of drug was recovered from the 1 to 10 m particles which were negatively charged. Hence, dierent particle size fractions of the aerosol can contribute dierently to the charge which can feasibly be studied by the ELPI method. ? 2003 Elsevier Ltd. All rights reserved. Keywords: MDI; Electrostatic charge; ELPI; Pharmaceutical aerosol; Inhaler 1. Introduction Pharmaceutical inhalation aerosols have become increasingly popular for delivery of drugs to the respiratory tract (Barnes, Drazen, & Rennard, 2002; Clark, 1995). Many physicochemical factors such as particle size, density, morphology, hygroscopicity, and surface energy will aect both the aerosol generation and subsequent deposition in the lungs after inhalation (Chew & Chan, 2002). * Corresponding author. Tel.: +61-2-93514450; fax: +61-2-93514391. E-mail addresses: wglover@pharm.usyd.edu.au (W. Glover), kimc@pharm.usyd.edu.au (H.-K. Chan). 0021-8502/$ - see front matter ? 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaerosci.2003.12.003