Dynamic Vapour Sorption

The water vapour or sorption properties of pharmaceutical materials such as excipients, drug formulations and packaging films are recognised as critical factors in determining their storage, stability, processing and application performance. Moisture sorption properties are routinely determined for pharmaceutical materials and have traditionally been evaluated by storing samples over saturated salt solutions of established relative humidities and then regularly weighing until equilibrium is reached.

However, there are a number of disadvantages with these methods, including:

• The prolonged period of time taken for the samples to reach equilibrium using a static method, often many days and sometimes many weeks.
• Inherent inaccuracies as the samples have to be removed from the storage container to be weighed which can cause weight loss or gain.
• Static methods necessitate the use of large sample sizes (typically >1gm).
• The highly labour intensive nature of static methods.