Void forming index: A new parameter for detecting microstructural transformation caused by powder agglomeration

Area of Science:

• Pharmaceutical Sciences
• Materials Science

Background:

• Powder agglomeration during storage reduces dry powder inhaler (DPI) performance.
• Capillary forces and crystalline transformations under humidity typically cause agglomeration.
• Correlating limited crystalline transformation with agglomeration is challenging.

Purpose of the Study:

• To investigate inverse gas chromatography (iGC) for direct detection of powder agglomeration.
• To establish a novel index for evaluating powder agglomeration in DPI development.

Main Methods:

• Utilized inverse gas chromatography (iGC) to measure lactose powder.
• Employed powder X-ray diffraction (PXRD) and dynamic vapor sorption (DVS) for comparison.
• Monitored pressure drop changes during iGC measurements.

Main Results:

• iGC detected significant pressure drop changes in lactose, unlike PXRD and DVS.
• Lactose powder agglomerated after iGC measurement, correlating with pressure drop.
• A novel Void Forming Index (VFI) was developed based on iGC pressure drop.

Conclusions:

• Pressure drop changes during iGC measurement indicate powder agglomeration onset.
• The Void Forming Index (VFI) offers a valuable tool for assessing powder agglomeration.
• VFI can aid in the development and optimization of dry powder inhalers.