Surface Measurement Systems (SMS) has provided instruments, chiefly dynamic vapor sorption systems, for solids characterization, including powders and fibers, for 18 years. Dr. Nishil Malde, International product manager at SMS told IBO, “SMS coined the phrase ‘Dynamic Vapour Sorption’ (DVS). We were the first company to develop and manufacture the first commercial, fully automated DVS instrument 18 years ago.” Since then, DVS has become an accepted technique, with multiple companies now offering DVS systems. With 60 employees, SMS has offices in North America, France and Germany. Its main office is in London.

DVS analysis determines the adsorption and desorption isotherms of solids. A sample is placed on a suspended microbalance within a temperature-controlled chamber, and subjected to an environment of water vapor or organic molecules. The solid’s mass changes, based on the rate at which molecules adsorb or desorb into its surface as a function of partial pressure, allow for the calculation of its isotherms. Once the isotherms are known, numerous characteristics can be deduced, such as a sample’s surface area and activation energy. Over time, SMS has differentiated its systems by adding capabilities, according to Dr. Malde, including “the ability to characterize the interaction of both water and solvent vapors in real time and the introduction of incorporating hyphenation techniques, such as performing Raman/NIR characterization in situ with DVS isotherm measurements.” The company also develops its own microbalances, with up to 0.1 mg resolution, for its DVS systems.

Although the company’s DVS instruments are used in many industries, their popularity in pharmaceuticals is greater the rest. According to Dr. Malde, “50%–60% of our market is in the pharmaceutical industry from pre-formulation to production support. Our remaining market share comprises food, biomaterials, cosmetics, personal care, polymer/fiber/films/paper, catalysts and chemical industries worldwide.” The DVS technique can characterize and measure numerous pharmaceutical properties including moisture stability and glass transition, the study of which is important for developing stable amorphous compounds at specific humidities. Another important application is the determination of low-amorphous content for drugs. Depending on the amorphous content, the stability, manufacturability and dissolution of a formulated drug may be compromised. Advantages of DVS over other gravitational methods for such detection include labor savings, the ability to study the entire partial pressure range of a sample, and higher throughput.

In addition to its standard DVS system, the DVS Advantage, SMS offers multiple DVS systems for specific markets and applications. These products include the DVS Vacuum for porous solids, and the DVS HT for high-throughput analysis of multiple samples. Applications for the DVS HT include quality control, polymorph screening and batch-to-batch analysis. The newest DVS system, the DVS Intrinsic, is designed specifically for water-only sorption markets, such as the food industry. Applications for this market include shelf-life prediction. A notable feature of the Intrinsic is its small footprint of 26 x 39 x 47 cm (0.85 x 1.28 x 1.54 ft).