Investigation of electrostatic properties of pharmaceutical propellants

Abstract

This study addresses the intricate field of measuring electrical volume resistivity in hydrofluorocarbons, specifically focusing on the measurement and application of resistivity in pharmaceutical propellants. Presented research introduces a novel method to measure resistivity in propellants used in metered-dose inhalers (MDIs) for respiratory diseases. It also scrutinizes the influence on the generated current in hydrofluorocarbon liquids produced by different valve stem materials and flow rates. The initial part of this dissertation provides an in-depth review of the resistivity cell designs, developed over the past three decades, emphasizing the practical aspects of cell design and highlighting the development of cells for testing the resistivity of refrigerants in liquid phase under high pressures. This review succinctly addresses contemporary standards, limitations, and constructional details of both academic and commercial cells and intends to serve as an instrumental guide for future researchers aiming to develop custom resistivity cells for dielectric liquids. It also looks into fundamentals of electrostatic charge and charge transfer as well as into previous research about electrostatic charge influence arising from the interaction with inhaler materials, inhaler designs and drug formulation. It explores measurement methods of abovementioned charge in previous studies. Further, this thesis examines the practical application of measuring the DC volume resistivity of pharmaceutical propellants like R134a, R152a, and R227ea, which are significant in treating respiratory diseases like asthma via metered-dose inhalers. The study elucidates the relationship between the electrical charging of aerosols, valve stem materials and the delivery efficiency of medicaments to the lungs, emphasizing the role of resistivity in this mechanism. Overall, this thesis integrates theoretical foundations with practical developments to advance the field of electrical volume resistivity measurement in liquid hydrofluorocarbons as well as their interactions with various polymer surfaces, offering significant contributions to the understanding of resistivity in refrigerants and pharmaceutical propellants and proposing innovative solutions to overcome the limitations of existing technologies.