3/17/2021 0 Comments Phase Dvs
Wikipedia is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization.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.
DVS was originally developed to replace the time and labor-intensive desiccators and saturated salt solutions to measure water vapor sorption isotherms. For water sorption isotherms, water relative vapor pressure is more commonly expressed as relative humidity. Phase Dvs Series Of StepIn a DVS experiment this is accomplished by exposing a sample to a series of step changes in relative humidity and monitoring the mass change as a function of time. The sample mass must be allowed to reach gravimetric equilibrium at each step change in humidity before progressing to the next humidity level. Then, the equilibrium mass values at each relative humidity step are used to generate the isotherm. Isotherms are typically divided into two components: sorption for increasing humidity steps and desorption for decreasing humidity steps. Sorption can be further divided into adsorption (sorbate located on the surface) and absorption (sorbate penetrates the bulk). The kinetic data (Figure 1a) shows the change in mass and humidity as a function of time. From the kinetic results, the rate of water uptake and water diffusion coefficients can be determined. The equilibrium mass values at the end of each humidity step were used to calculate the sorption and desorption isotherms (Figure 1b). The difference in water vapor uptake between the sorption and desorption isotherms is called the hysteresis. The shape and location of the isotherm hysteresis can elucidate information about the sorption mechanism and sample porosity. Although an isotherm experiment is the most common use of a DVS instrument, humidity (or other vapor) ramping experiments can be performed to investigate vapor-induced phase changes. ![]() Both equilibrium vapor sorption isotherms and vapor sorption kinetic results can yield vital information for materials ranging from pharmaceuticals to fuel cells. Although water sorption experiments are most common, the use of organic vapor in DVS experiments can reveal additional sample properties. The below sections highlight how DVS experiments are utilized in several industries. Gravimetric vapor sorption experiments are one of the most sensitive methods for determining amorphous contents, 5 6 7 which may have a detrimental impact on the stability, manufacturability and dissolution characteristics of the formulated drug product. ![]() Phase Dvs Skin Samples HasThe hydration behavior of skin samples has also been studied by DVS. Other moisture sorption applications related to the personal care industry include the dehydration of contact lenses and superabsorbent polymers. Water is typically supplied to the fuel cell by humidifying the gas feed stream. The level of hydration within the proton exchange membrane is vital to its performance: if the hydration level is too low, the polymers exhibit greatly reduced ionic conductivity; 25 if hydration level is too high, excess water can flood the pores in the gas diffusion layer and impede mass transport within the electrode structure. For these reasons, DVS has been used to study the water sorption and transport properties of proton exchange membranes. By using this site, you agree to the Terms of Use and Privacy Policy.
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