Vapour Sorption Techniques for Particle Engineering - poster
Sabiyah Ahmed¹, Meishan Guo¹, Majid Naderi¹, Manaswini Acharya¹, and Daniel Burnett^2
1Surface Measurement Systems Ltd., Alperton, London, HA04PE
²Surface Measurement Systems Ltd., 2125 28th Street SW, Suite 1, Allentown, PA 18103, USA
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Drug substances intended for drug delivery to the lungs typically require particle size reduction. High energy processes are typically utilized to produce particles smaller than 10 μm but these processes are also known to influence crystallinity, which can lead to a reduction in physical and sometimes even chemical stability. Therefore, these materials may be conditioned following micronization before further processing. Such a “deamorphization” step typically involves the treatment of the materials with an appropriate solvent that plasticizes the material and induces crystallization. While the selection of the solvent is critical, the degree of control over the deamorphization process is also very important. A treatment time that is too short may lead to incomplete crystallization of the material, while overtreatment may cause partial dissolution and agglomeration.

In order to estimate the appropriate treatment time, knowledge of the crystallization kinetics may be predicted from Dynamic Vapour Sorption  (DVS) studies. Changes in surface chemistry; from a heterogeneous surface property to a homogeneous and low wettability surface property would affect the variability in powder flow behavior and agglomeration which may be monitored using Inverse Gas Chromatography Surface Energy Analyser (IGC-SEA).

Water vapor has been shown to induce crystallization for milled salbutamol sulphate, with one-step mechanism. DVS can be used to investigate moisture-induced crystallization kinetics, over a wide range of temperature and humidity conditions.

Silanisation process has clearly improved the flow properties of D-mannitol in a low-stress environment. iGC-SEA is a fast and accurate way to predict agglomeration and powder flow behavior, using surface energy heterogeneity and work of cohesion as the parameters.