Quantification of free and bound water in selected materials using dielectric and thermo-coulometric measurement methods

Abstract

Broadband electromagnetic characterization offers useful tools for the quantitative estimation of water content in a insulating solid materials. However, the correlation between electromagnetic characteristics and the amount of water in solids needs to be characterized using precise direct measurement methods. In this study, a two-port coaxial transmission cell has been characterized for water content estimation based on a study with the thermo-coulometric water detection method. The latter allows us to determine the proportions of the different water bonding forms that can exist in the material. The purpose of this paper is to provide a dielectric relaxation behavior study of the kaolinite clay from 10 MHz to 1.5 GHz, which was preceded by an experimental analysis of α-D-lactose monohydrate and the calcium oxalate monohydrate, which have stable water content under various humidity conditions.

Temperature Dependence of Sorption

“…At low a 2 (namely, high ϵ = − RT ln a 2 , i.e., ϵ > 4000 J mol –1 ), T ( s 2 – s 2 0 ) changes little. This large negative and near-constant T ( s 2 – s 2 0 ) signifies the restriction of the water molecule, which is reminiscent of the “bound water” hypothesis that has been invoked in biophysics and food science. − While the increase (i.e., becoming less negative) of T ( s 2 – s 2 0 ) at higher a 2 (i.e., lower ϵ) shows that water molecules are less restricted. This is reminiscent of the oft-used previous speculation of the “free water”, − yet our theory can provide quantitative measures on the state of sorbates directly from their isotherms.…”

“…This large negative and near-constant T ( s 2 – s 2 0 ) signifies the restriction of the water molecule, which is reminiscent of the “bound water” hypothesis that has been invoked in biophysics and food science. − While the increase (i.e., becoming less negative) of T ( s 2 – s 2 0 ) at higher a 2 (i.e., lower ϵ) shows that water molecules are less restricted. This is reminiscent of the oft-used previous speculation of the “free water”, − yet our theory can provide quantitative measures on the state of sorbates directly from their isotherms. Thus, the fluctuation theory sheds light on the state of sorbates based on the temperature dependence of sorption isotherms beyond the assumptions made by sorption models.…”

On the influence of water on THz vibrational spectral features of molecular crystals

“…Furthermore, water molecules can interact with pharmaceutical compounds in numerous ways, which can dramatically affect the performance of a final dosage form. For both food science and pharmacology, the role of water in mono-and polysaccharides is extremely interesting [26][27][28][29][30] . Overall, understanding the role of water in molecular crystals and macromolecules is still an actual challenge that can be tackled using vibrational spectroscopy.…”

“…For both food science and pharmacology, the role of water in mono-and polysaccharides is extremely interesting. [26][27][28][29][30] Overall, understanding the role of water in molecular crystals and macromolecules is still an actual challenge that can be tackled using vibrational spectroscopy.…”