title: Measuring Bipolar Charge and Mass Distributions of Powder Aerosols by a Novel Tool (BOLAR).
abstract: The Bipolar Charge Analyzer (BOLAR) was evaluated for measuring bipolar electrostatic charge and mass distributions of powder aerosols generated from a dry powder inhaler. Mannitol powder (5, 10, and 20 mg) was dispersed using an Osmohaler inhaler into the BOLAR at air flow rates of 30 or 60 L/min. As the aerosol sample was drawn through the BOLAR, the air flow was divided into six equal fractions. Five of them entered individual detection tubes with a defined cutoff diameter in the range of 0.95 to 16.36 μm (depending on the flow rate) and the remaining (i.e., the sixth) fraction passed through a reference chamber. The aerosols that entered the detection tubes were separated according to the particle charge polarity (positive, negative, or neutral) and charge was measured by separate electrometers. The deposited powder of a single actuation from the inhaler was chemically assayed using high performance liquid chromatography. Additionally, the aerosol measurements were conducted on a modified Classic Electrical Low Pressure Impactor (ELPI) for comparison of the net specific charge per size fraction. Spray-dried mannitol carried significantly different positively and negatively charged particles in each of the five defined particle size fractions. The charge-to-mass ratio (q/m) of positively charged particles ranged from +1.11 to +32.57 pC/μg and negatively charged particles ranged from -1.39 to -9.25 pC/μg, resulting in a net q/m of -3.08 to +13.34 pC/μg. The net q/m values obtained on the modified ELPI ranged from -5.18 to +4.81 pC/μg, which were comparable to the BOLAR measurements. This is the first full report to utilize the BOLAR to measure bipolar charge and mass distributions of a powder aerosol. Positively and negatively charged particles were observed within each size fraction, and their corresponding q/m profiles were successfully characterized. Despite some potential drawbacks, the BOLAR has provided a new platform for investigating bipolar charge in powder aerosols for inhalation.
authors.affiliation: Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wong
authors.affiliation: Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Lin
authors.affiliation: Department of Pharmacology and Pharmacy, Li Ka Shing Faculty of Medicine, The University of Hong Kong , Hong Kong SAR, China.
authors.forename: Philip Chi Lip
authors.initials: PC
authors.lastname: Kwok
authors.affiliation: Dekati Limited , Kangasala FI-36240, Finland.
authors.forename: Ville
authors.initials: V
authors.lastname: Niemelä
authors.affiliation: Pharmaxis Limited , Frenchs Forest, New South Wales 2086, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Crapper
authors.affiliation: Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Hak-Kim
authors.initials: HK
authors.lastname: Chan
mesh_terms: D000280:Administration, Inhalation; D000336:Aerosols / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D008353:Mannitol / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D009330:Nebulizers and Vaporizers; D010316:Particle Size; D011208:Powders / Q000737:chemistry*; D055672:Static Electricity; D013678:Technology, Pharmaceutical / Q000295:instrumentation*
chemical_list: D000336:Aerosols; D011208:Powders; D008353:Mannitol
keywords: Bipolar Charge Analyzer (BOLAR); Electrical Low Pressure Impactor (ELPI); Osmohaler; spray-dried mannitol powder; triboelectrification