GraviSorb Series – Gravimetric Water Sorption Analyzers
The GraviSorb is a fully automated, gravimetric, multi-sample, high load capacity, high resolution, and dynamic water vapor sorption analyzer. It measures adsorption and desorption isotherms of water vapor both accurately and sensitively, including sorption kinetics, with minimal operator involvement. The weight of up to 12 samples is monitored and recorded as the relative humidity is automatically varied by blending dry carrier gas with a saturated gas stream.
The carousel balance design of the GraviSorb allows increased analysis throughput by simultaneous investigation of up to 12 different samples, or 11 + 1 if one station is running an empty sample chamber or even a reference material for direct comparison. The GraviSorb is an ideal solution for the determination of water uptakes for research and quality assurance.
The complete automatic measuring process together with the precise balance, broad climate range and user-friendly software make it the ideal instrument for high sample throughput with a minimum of costs and maintenance.
- Complete automated system: automatic weighing & changing of climate according to settings of the user
- Easy-to-use, with a minimum of maintenance
- User-friendly software with advanced Excel export
- Results storage in a database with backup function
- High sample weight capacity, up to 125 g (up to 250 g as an option)
- High resolution & precision by using a 0.01 mg resolution balance
- 12 (11+1) samples can be measured simultaneously
Isotherms: Mass change as a function of changing relative humidity, increasing mass during adsorption (increasing %RH), decreasing mass during subsequent desorption (decreasing %RH)
Kinetics: time-dependent sorption studies give the rate of ad- and desorption
Effect of Temperature: isotherms and kinetics change as a function of temperature. Can be used to yield sorption enthalpies.
Literature and Norms
- Isothermal measurement of the sorption of vapours at solids (DIN 66138:2008-09)
- ASTM C 1104/C 1104Ma:2013
Dynamic Vapor Sorption
Dynamic Vapor Sorption (DVS) is a gravimetric sorption technique the measures the speed and volume by which a solvent is absorbed by a sample. For example a dry powder absorbing water.
Dynamic Vapor Sorption does this by varying the vapor concentration surrounding the sample and measuring the change in mass this produces. Most commonly used is water vapor however it is possible to use a broad range of organic solvents.
Dynamic Vapor Sorption is a trusted measurement tool and a vitally important part of quality control and is often used within the packaging arena, measuring efficacy, permeability as wellas the effects of temperature and humidity products and packaging.
Measuring Methods – Dynamic Vapor Sorption
Water vapor sorption follows the same physical rules and principles as gas sorption. The difference with gas sorption is that condensation of vapors must not influence the results of the measurement.
Because of this, the water uptake is often measured gravimetrically in a dynamic, humid gas flow (DVS – Dynamic Vapor Sorption) – these experiments can be carried out for many materials, such as pharmaceutical products, food, packing materials, building materials etc.
Static-Volumetric Vapor Sorption
Water vapor sorption can also be measured static-volumetrically in a measuring system with calibrated volume by measuring the equilibrium pressure. Corresponding analyzers exhibits a heated volume system, so that condensation in the manifold, valves or lines is avoided.
The liquid is stored in a glass-vessel, which is connected to the manifold with a valve/line-system. First the glass-vessel is evacuated to remove the air then the desired vapor phase is build up above the liquid phase. Dosing of this vapor into the measuring cell removes vapor from the manifold, more liquid from the glass-vessel is evaporated until the equilibrium state between liquid and gas phase is reached again.
Determination of the water sorption isotherm (ad- and desorption) are carried out fully automatically and different possibilities are offered for the analysis of isotherms: Determination of surface areas, pore volumes or heats of adsorption.
Mixture Adsorption of Vapors
Practical questions can be directly studied, e.g. investigation of the sorption behavior of humid adsorbents in a dry gas flow or the sorption behavior of adsorbents under a humid gas-vapor flow.
There is a huge difference between these two cases and both experiments can easily be prepared. Such investigations can be done flexibly with the mixSorb series including the coupling to external analytical devices to determine e.g. trace elements.
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