Application note 101: Moisture Sorption Properties of Pharmaceutical Materials Studied by Dynamic Vapour Sorption

Dynamic Vapour Sorption (DVS) has long been used for investigating the interaction of water vapour with active pharmaceutical ingredients (API’s), excipients and pharmaceutical formulations. This overview application note summarises several examples of using DVS for pharmaceutical-related applications including: hygroscopicity, moisture content, moisture-induced phase transitions, hydrate formation/loss, and amorphous content.


The water vapour or moisture 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. According to the US Pharmacopeia, moisture is not treated as an impurity, but water in a drug substance should be monitored and controlled as strictly as possible. (USP general chapter 1241). Further, the moisture content affects crystallinity and influences storage modulus, permeability, density and melting point of pharmaceutical products. In particular to amorphous materials, moisture can significantly alter the glass transition temperature, and even initiate spontaneous transformation to the crystalline form. Additionally, water facilitates hydrolysis and induces drug degradation. Finally, water content is routinely used in determining the dry and solvent-free assay value of a drug substance.

For the above reasons, a rapid, highly-sensitive and automated method to study moisture sorption properties is desired. Hence, the invention of the Dynamic Vapour Sorption (DVS) instrument by Surface Measurement Systems in the early 1990’s. Today, the DVS is widely used across numerous industries for investigating the vapour sorption properties of solids, fibres, gels, particulates, and composite materials. This application note summarises several DVS applications related to drugs, excipients, and pharmaceutical ingredients.

App 101

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