Vapor equilibrium technique water control

Falk et al. conducted early FTIR studies of the structure of water in this ionomer, and the papers of these investigators serve as an excellent resource for the various band assignments, as tabulated in the book edited by Eisenberg and Yeager. The results of these studies were significant on a quantitative basis, in part, due to their careful control of water content by a vapor equilibrium technique that allowed for reproducibility as well as precise determination of the H20/SOs ratio. 

In the author s laboratory, two experimental techniques have been developed for controlling the water content. In the vapor equilibrium technique the membrane is suspended in a hygrostatic... 

Solid-phase microextraction is controlled by diffusion rates and partition effects. In typical quantitative analyses, for this technique to be reproducible, the extraction process should continue until the partitioning events reach equilibrium and all variables affecting the partitioning must be controlled. For a two-phase system, the extraction is dependent on the analyte s partition coefficient and the volumes of the solid phase and the water. In the headspace technique, equilibrium must be reached between all three phases the water, the vapor, and the solid phase. 

Miscellaneous techniques. Recently the rate of evaporation of water or other liquids from a wetted porous material imder diffusion-controlled conditions was shown to depend on the size of pores of the material [193]. This fact was interpreted in terms of the dependence of the equilibrium vapor pressure above the sample on the radius of the meniscus of the liquid in the pores. This technique is sensitive and relatively simple. However, estimation of the pore radius from the rate of evaporation is again based on the use of the Kelvin equation in a wide range of relative pressures and, therefore, inherits all the uncertainties of the technique and incorporates some additional assumptions. This technique reveals two maxima in the pore size distribution of the water-wetted hypercrosslinked material prepared from a styrene-0.3%... 

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