Dynamic Vapor Sorption (DVS)
Dynamic Vapor Sorption (DVS) is a gravimetric technique that measures how quickly and how much of a solvent is absorbed by a sample: such as a dry powder absorbing water. It does this by varying the vapor concentration surrounding the sample and measuring the change in mass which this produces. Water vapor is most commonly used, but it is also possible to use a wide range of organic solvents.
Dynamic Vapor Sorption is a valued tool in laboratories all over the world, within R&D, from polymorphism and compound stability studies to bulk and surface sorption effects of water and organic vapours. It is a vital part of quality control analysis techniques for both scale-up and production, and can even be found within the packaging area, measuring efficacy, permeability, and the effects of humidity and temperature on the samples within the packaging.
A schematic of a Dynamic Vapor Sorption (DVS) automated gravimetric sorption system is shown in Figure 1. The Surface Measurement Systems DVS instrument, now in use by many companies and research laboratories world-wide, rapidly measures uptake and loss of moisture or organic vapours by flowing a carrier gas at a specified relative humidity (or partial pressure) over a sample (which can weigh between 1 mg and 4 g) suspended from the weighing mechanism of an ultra-sensitive recording microbalance. This particular microbalance, the Surface Measurement Systems Ultrabalance, is used as it is capable of measuring changes in sample mass lower than 1 part in 10 million, providing unrivalled long-term stability required for accurate measurements of vapour sorption phenomena, which may take from minutes to days to complete depending upon the sample size and material. Indeed, a major factor in determining the sorption behaviour of materials is the need to establish rapid sorption equilibrium, therefore the DVS instrument allows sorption behaviour to be accurately determined on very small sample sizes (typically 10 mg), thus minimising the equilibration time required.
The DVS instrument is a fully automated instrument operating under the control of a dedicated PC computer. The DVS control software package supplied with the instrument provides a flexible and easy to use interface for setting up and running sorption /desorption experiments on the DVS instrument. In addition, the DVS Data Analysis Suite, which runs from within Microsoft Excel®, provides a powerful environment for rapid plotting and quantitative analysis of data.