The use of Quartz Crystal Microbalance as an analytical tool to monitor particles/surface and particle/particle interactions in dry ambient and pressurized conditions: a study using common inhaler components

Metered dose inhalers (MDI) and multidose powder inhalers (MPDI) are commonly used for the treatment of chronic obstructive pulmonary diseases and asthma. Currently, analytical tools to monitor particle/particle and particle/surface interaction within MDI and MPDI at the macro-scale do not exist. A simple tool capable of measuring such interactions would ultimately enable quality control of MDI and MDPI, producing remarkable benefits for the pharmaceutical industry and the users of inhalers. In this paper, we have investigated whether quartz crystal microbalance (QCM) could become such a tool. QCM was used to measure particle/particle and particle/surface interactions on the macro scale, by additions of small amount of MDPI components, in powder form into a gas stream. The subsequent interactions with material on the surface of the QCM sensor were analyzed. Following this, the sensor was used to measure fluticasone propionate, a typical MDI active ingredient, in a pressurized gas system to assess its interactions with different surfaces under conditions mimicking the manufacturing process. In both types of experiment QCM was capable to discriminate interactions of different components and surfaces. The results have demonstrated that QCM is a suitable platform for monitoring macroscale interactions and could possibly become a tool for quality control of inhalers.