Introduction of the electrical Next Generation Impactor (eNGI) and investigation of its capabilities for the study of pressurized metered dose inhalers

Purpose: To introduce the design of the electrical Next Generation Impactor (eNGI), and validate its proposed function as a method of electrostatic characterization for pressurized metered dose inhaler (pMDI) formulations. Methods: Flixotide® (fluticasone propionate), Ventolin® (salbutamol sulphate), and QVAR® (beclomethasone dipropionate) were used as model pMDIs in this study. At an airflow rate of 30 l/min, five individual actuations of each pMDI were introduced into the electrical low-pressure impactor (ELPI), Next Generation Impactor (NGI), and the eNGI. Charge profiles for each actuation were measured by the ELPI and eNGI, while mass profiles were recorded by the all three impactors. Results: The difference in estimated mass median aerodynamic diameters and geometric standard deviations for all pMDIs using the NGI and eNGI were not found to be statistically significant (p < 0.05). The mean charge profiles from the ELPI and eNGI overlap well between 0.54 and 6.61 μm (Flixotide® and Ventolin®), and between 0.615 and 11.72 μm (QVAR®), where the majority of the impacted doses were collected. Conclusion: For the analysis of pMDIs, the eNGI is comparable to the NGI in measuring particle size distribution, while still being comparable to the ELPI in measuring charge distribution.