Figure 2. Shows DVS Isotherm Plots for one sample with multiple solvents
Benefits of using the method
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, from pharmaceutical, food, personal care and health to energy, aerospace, agriculture and environment and building materials industries.
DVS 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.
DVS is also a widely use instruments in many by laboratories and recognised by Pharmacopoeia for the characterisation of solid state dosage forms in the pharmaceutical industry.