Dynamic Vapor Sorption
Dynamic vapor sorption (DVS) is a gravimetric technique that measures the quantity, and how quickly water vapor is adsorbed and/or absorbed by a material, such as cement, or an active pharmaceutical ingredient. Accurate measurements are achieved by controlling the temperature and humidity electronically, allowing excellent instrument baseline stability as well as accurate control of the generated relative humidity.
DVS instruments work by flowing precisely controlled concentrations of water vapors in dry air over a sample at a known flow rate and temperature. The sample rests on a digital microbalance which detects the sorption/desorption of water vapor through the increase or decrease in mass of the material as the relative humidity (RH) varies. DVS instruments can also perform isoactivity (or isohume) measurements in which materials are kept under constant RH conditions while linearly or stepwise varying the temperature.
Additionally, DVS instruments can be set up to assess permeability of water vapor through a thin barrier, e.g. packaging materials or membranes. The sample pan is filled with a known desiccant (e.g. molecular sieves), sealed with the membrane of interest, and exposed to high RH levels. Alternately, the sample pan is filled with water or saturated salt solutions with known water activity, sealed with the membrane of interest, and exposed to low RH levels.
Moisture sorption properties of a material can provide critical information on the stability, processing, performance, and storage of materials. Moisture sorption analysis is applicable to pharmaceuticals, food products, packaging, personal care products, fibers, building materials and agricultural materials.
Advantages
- Relatively quick way of obtaining the water sorption and desorption isotherm of the sample (typically in 3-5 days) compared to traditional methods (typically weeks to months)
Considerations
- Water vapor only (some organic solvents can be used for static vapor sorption only)
- Maximum %RH achievable depends on analysis temperature and instrument used
Sample Requirements
Recommended sample quantity is 1 to 100 grams. The sample pan has a base diameter of 50 mm and a depth of 11 mm.
This instrument is able to analyze up to 11 samples at a time.
Detection Range
The balance resolution is ± 10 µg (up to 100 g) or ± 100 µg (up to 220 g). The temperature range for analysis is 15 to 40°C, and the max relative humidity (RH) depends on analysis temperature (e.g. 0 to 95% RH at 25°C, 0 to ~70% RH at 15 or 40°C).
Data Reported
Change in mass versus either increase / decrease in %RH or in temperature (if %RH held constant). Permeability analysis is available upon request.
Sample Reports
Instrumentation
The ProUmid Vsorp Plus is used for DVS analysis at PTL.
