Solid particles injected directly from four different pressurised metered dose inhalers were stably captured in an optical trap and examined online via Raman spectroscopy. Micron-sized particles of inhalable drugs were captured and analysed at a range of relative humidity (RH) conditions. One drug found to be hygroscopic was also analysed at temperatures closer to the inside of the human body. This technique represents a viable method for testing the suitability of specific particle size ranges of inhalable drugs with hygroscopic properties.
