AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Macro-Raman Spectroscopy on Respirable Particles Collected by a Single-nozzle Cascade Impactor
HUI WANG, Lisa Williams, Susan Hoe, David Lechuga-Ballesteros, Reinhard Vehring, University of Alberta
Abstract Number: 474 Working Group: Instrumentation and Methods
Abstract A Monte-Carlo model was developed to predict the minimum sample volume required for representative sampling from potentially heterogeneous microparticle-based powder samples, characterized by different particle size distributions and compositions. Simulation on commercial carrier free pressurized metered dose inhaler (pMDI) Seretide$^® 50, containing 50 µg fluticasone propionate (FP) and 25 µg salmeterol xinafoate (SX) each dose, and lactose-carrier based dry powder inhalers (DPI) Seretide$^®, consisting of 100, 250, or 500 µg FP and additional 25 µg SX each dose, indicated that at least millions of particles need to be sampled to achieve less than 3% relative sampling error with high confidence (95%) after 5 independent sampling events. A single-nozzle impactor, utilizing standard scanning electron microscopy (SEM) stub as its impaction plate, was then designed and manufactured for the collection of highly dispersed respirable aerosols for subsequent bulk property analysis. One single dose of pMDI Seretide$^® 250, containing 250 µg FP and 25 µg SX, was actuated into the impactor, and particles were concentrated onto a stage with selected cutoff diameter of 1.05 µm. The new single nozzle impactor successfully collected about 200 µg of the 275 µg dose. Collected particles were directly transferred for ultramicroscopic morphology characterization and also filled into a 0.16µL-sample cavity of a custom designed dispersive macro-Raman instrument for spectroscopic analysis. In comparison to the spectrum of powders extracted from the pMDI canister by a traditionally used freezing-cutting-evaporation method, a separate spectrum with less than 3% spectral differences was acquired, indicating representative impactor sampling and macro-Raman measurement.