Dynamic water vapor sorption

The Dynamic Vapor (English Dynamic Vapor Sorption , DVS) is a gravimetric measurement method for the sorption of water vapor to investigate to solid. In 1991, Daryl Williams developed the measurement method in which the weight gain and loss of a solid after a change in the ambient humidity is analyzed using a microfine balance . In particular, the time saved (10–100 times faster than current methods) when measuring hygroscopicity ensured that this method was quickly implemented in the pharmaceutical industry.

construction

The device for measuring dynamic water vapor sorption consists of a closed chamber in which a control unit controls the temperature and the humidity can be set from 0-100%. In this chamber there is a micro-scale that measures the changes in weight of the solid sample. A computer analyzes these changes in weight and regulates the humidity.

procedure

DVS diagram for microcrystalline cellulose . On the Y-axes the rel. Humidity and weight gain of the sample can be read. The X-axis indicates the time.

DVS diagram for microcrystalline cellulose. The weight gain is compared to the rel. Humidity applied. The lower measured values reflect the mass values when the air humidity increased. The upper measured values belong to the decreasing series of measurements.

A few milligrams of sample (usually 10 mg) are placed in the device and measured. First, at 0% humidity, the sample is weighed to the mass constant. The humidity is then increased (usually in 10% steps) and it is waited again until the sample no longer shows any change in weight. This is done up to a humidity of 100%. Then the humidity is lowered in equal steps and the changes in weight are observed again. At the end, the weight of the sample or the weight change in% is evaluated against the relative humidity in a diagram. Due to the steepness, shape and hysteresis of the diagram, conclusions can be drawn about hygroscopic properties, porosity, crystallinity and stability.

use

The method is used in particular in the pharmaceutical industry, but also in the food industry, to characterize active ingredients or auxiliary substances in more detail. The knowledge about the sorption behavior of a substance in relation to air humidity is crucial in order to be able to make statements regarding stability and to develop necessary stabilization concepts (e.g. airtight packaging).

Since the size and number of pores in powder particles also change the diagram, the DVS can be used for a more detailed characterization of powders or granules, especially to ensure consistent quality.

Individual evidence

^ The Use of Dynamic Vapor Sorption Method in the Determination of Water Sorption Limit and Setting Specification for Drug Substance. Retrieved February 20, 2017 .
↑ Carl L. Levoguer and Daryl R. Williams: The Characterization of Pharmaceutical Materials by Dynamic Vapor Sorption . Ed .: Surface Measurement Systems Ltd. November 24, 2006 ( micromeritics.com [PDF]).
↑ Sneha Sheokand, Sameer R. Modi, Arvind K. Bansal: Dynamic Vapor Sorption as a Tool for Characterization and Quantification of Amorphous Content in Predominantly Crystalline Materials . In: Journal of Pharmaceutical Sciences . tape 103 , no. 11 , p. 3364-3376 , doi : 10.1002 / jps.24160 .

[1] The Use of Dynamic Vapor Sorption Method in the Determination of Water Sorption Limit and Setting Specification for Drug Substance. Retrieved February 20, 2017 .

[2] Carl L. Levoguer and Daryl R. Williams: The Characterization of Pharmaceutical Materials by Dynamic Vapor Sorption . Ed .: Surface Measurement Systems Ltd. November 24, 2006 ( micromeritics.com [PDF]).

[3] Sneha Sheokand, Sameer R. Modi, Arvind K. Bansal: Dynamic Vapor Sorption as a Tool for Characterization and Quantification of Amorphous Content in Predominantly Crystalline Materials . In: Journal of Pharmaceutical Sciences . tape 103 , no. 11 , p. 3364-3376 , doi : 10.1002 / jps.24160 .