Vapour pressure sorption analysis

More recent examples of the construction of energy-temperature diagrams for drug polymorphs include those published by Schmidt and co-workers for two local anaesthetics, hydroxyprocaine hydrochloride (HPCHC, Figure 9, 11) and salicaine hydrochloride (SLCHC, Figure 9,12) [49,50]. Comprehensive solid-state analysis of these compounds included HSM, DSC, TG, FUR and Raman spectroscopy, SSNMR, PXRD, single crystal XRD and vapour pressure sorption analysis. 

X-ray diffraction methods (powder, single crystal) Spectroscopy (UV, IR, Raman, solid-state NMR) Thermal analysis, microcalorimetry, solubility determination, vapour pressure determination Moisture sorption Microscopy and micromeritics... 

This reasoning was followed by Flory and Rehner in their analysis of swelling networks. We may also calculate the equilibrium from a free energy which does not contain 0, provided the result is corrected afterwards by means of equation (78). Clearly, this method is equivalent, since /c>/7z == ( 0/dV)Vo = —upo, where a represents the hydrostatic pressure due to network interlinking. Barkas and Cassie have used this method to correct the sorption isotherm of wood and of wool. In Fig. 21 the drawn curve represents the sorption of water by wool measured directly. The swelling involved in this sorption, however, is opposed by forces whose Sorption magnitude may be estimated from stress-strain data in the stretch of wool. If the vapour pressure is corrected according to equation (78), one finds the much lower vapour pressures of the dotted curve. This curve extends no further than to 50% relative vapour pressure. 

Dronen DM, Reineccius GA. 2003. Rapid analysis of volatile release from powders using dynamic vapour sorption atmospheric pressure chemical ionization mass spectrometry. Journal of Food Science 68 2158-2162. 

Rapid analysis of volatile release from powders using dynamic vapour sorption atmospheric pressure chemical ionization... 

Solubility of Gaseous Mixtures Comparison with Experimental Data. The experimental determination of the solubility of gas mixture components in a solid polymer is a very complicated task relative to the measurement of solubility of a pure gas or vapour. Indeed, very few mixed gas sorption data are available in the technical literature. To compare with predictions of the NELF model, only the experimental data for the solubility of GO2/C2H4 mixtures in PMMA at 35°C (4, 75, 76) will be considered in this article. Since the volume dilation produced by the gas mixture is not available, the analysis of the data is confined to the low pressure range, where the swelling of the glassy polymer may be neglected. Indeed, in the calculation which follows the non-equilibrium solubility is estimated from the NELF model assuming... 

In the sorption experiments, a polymeric sample is suspended to a quartz spring balance, having a measured extension, in a vacuum chamber. A vapour or a gas is then introduced and maintained at a constant pressure. The gas or vapour dissolves and diffuses into the polymer and the weight gain is gravimetrically measured. The analysis is focused on the initial part of the mass-gain curves. 

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