title: Determination of reference ultrasound parameters for model and hydrofluoroalkane propellants using high-resolution ultrasonic spectroscopy.
abstract: The aim of this research was to determine the reference ultrasonic velocity (v) and attenuation coefficient (alpha) for 2H, 3H-perfluoropentane (HPFP), 1,1,1,2-tetrafluoroethane (HFA-134a) and 1,1,1,2,3,3,3-tetrafluoroethane (HFA-227) propellants, for the future purpose of characterising pressurised metered dose inhaler (pMDI) formulations using high-resolution ultrasonic spectroscopy (HRUS). Perfluoroheptane (PFH) was used as a reference material for HPFP. With its velocity and attenuation coefficient determined at 25 degrees C, HPFP was subsequently used as a reference for HFA-134a and HFA-227. It was found that there is a linear decline in ultrasonic velocity with an increase in temperature. As with HPFP, the ultrasonic velocity of HFA-134a and HFA-227 were successfully calculated at 25 degrees C. However, the difference in density and viscosity between reference and sample prevented accurate determination of reference attenuation coefficient for the hydrofluoroalkanes. With ultrasonic velocity alone, dispersion concentration and stability monitoring for experimental pMDI formulations is possible using HRUS. However, at this point in time measurement of particle size is not feasible.
authors.affiliation: Advanced Drug Delivery Group, Faculty of Pharmacy, University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Hoe
authors.forename: Paul M
authors.initials: PM
authors.lastname: Young
authors.forename: Philippe
authors.initials: P
authors.lastname: Rogueda
authors.forename: Daniela
authors.initials: D
authors.lastname: Traini
mesh_terms: D000280:Administration, Inhalation; D000335:Aerosol Propellants; D002626:Chemistry, Pharmaceutical; D005466:Fluorocarbons / Q000737:chemistry; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D036501:Metered Dose Inhalers; D008956:Models, Chemical; D009038:Motion; D012016:Reference Values; D019141:Respiratory System Agents / Q000008:administration & dosage / Q000737:chemistry; D013057:Spectrum Analysis / Q000592:standards; D013678:Technology, Pharmaceutical / Q000379:methods* / Q000592:standards; D013696:Temperature; D014465:Ultrasonics; D014783:Viscosity; D010420:Pentanes
chemical_list: D000335:Aerosol Propellants; D005466:Fluorocarbons; D006845:Hydrocarbons, Fluorinated; D019141:Respiratory System Agents; C008806:perfluoropentane; D010420:Pentanes; C094049:apaflurane