Water vapor sorption on morphine sulphate was studied in a twin double sorption microcalorimeter at 25°C. The vapor sorption isotherm and the differential heats of sorption were determined simultaneously from dry condition to a water activity of 0.99. Two well resolved hydration steps were obtained on the sorption isotherm at water activities of 0.01 and 0.22 corresponding to the formation of dihydrate and pentahydrate of morphine sulphate. They were accompanied by constant values of the differential heats of sorption: –24 kJ mol–1(H2O) for the dihydrate formation and –10 kJ mol–1(H2O) for the pentahydrate formation.The calorimetrically obtained sorption isotherms were compared with the results of Karl Fisher titrations of morphine sulphate samples equilibrated at different water activities. The appearance of a liquid phase in the morphine sulphate at high water activities is discussed on the basis of the obtained differential heats of sorption and measured heat capacities of morphine sulphate at different water activities.
The gravimetric measurement of the moisture content of solids is discussed in comparison to other usual methods. Results of
measurements of silica gel are reported. Furthermore, we inform on standardisation work.
The amorphous content of different Desferal samples was quantified by recording its recrystallization using isothermal microcalorimetry in a static as well as in a flowing humid atmosphere. Furthermore water vapor sorption gravimetry was performed for the same purpose. These analytical methods result in a quantitative signal directly dependent on the content of the amorphous phase (recrystallization, water sorption equilibrium). Their sensitivity allows the detection of amorphous content below 1%. Methods are compared and advantages and disadvantages are discussed.
Authors:H. Bahaj, M. Bakass, C. Bayane, J. P. Bellat, M. Benchanaa, and G. Bertrand
Several theoretical and experimental studies examined watervaporsorption on different solid surfaces [ 1 – 4 ]. Indeed, the choice of adsorbent solid depends on adsorption capacity, adsorption kinetic, thermal
Authors:D. Berkün, D. Balköse, F. Tıhmınlıoǧlu, and S. Altınkaya
Two types of films consisting of sodium salt of carboxymethyl cellulose (NaCMC) and hydroxypropyl cellulose (HPC) as film
forming materials and glycerin as plasticizer were prepared, characterized and their water vapour sorption properties were
The water sorption isotherms of the films were measured using a magnetic suspension balance. Results show that diffusion of
water vapour in NaCMC based film is faster than that in HPC based films, due to the heterogeneous structure and larger pore
dimensions of the NaCMC films.
Authors:A. Schmidt, V. Niederwanger, and U. Griesser
Two polymorphic forms, a dioxane solvate and the amorphous form of the local anaesthetic drug prilocaine hydrochloride (N-(2-methylphenyl)-2-propylamino
monohydrochloride, PRCHC) were characterized by thermal analysis (hot stage microscopy, differential scanning calorimetry,
thermogravimetry), vibrational spectroscopy (FTIR, FT-Raman-spectroscopy), powder X-ray diffractometry and water vapor sorption
analysis. The formation and thermodynamic stability of the different solid phases is described and presented in a flow chart
and an energy temperature diagram, respectively. Mod. I (m.p. 169C) is the thermodynamically stable form at room temperature and present in commercial products. This form crystallizes
from all tested solvents except 1,4-dioxane which gives a solvate with half a mole of 1,4-dioxane per mole PRCHC. Mod. II
occurs only on desolvation of the dioxane solvate and shows a lower melting point (165.5C) than mod. I and a lower heat
of fusion. Thus, according to the heat of fusion rule, mod. II is the thermodynamically less stable form in the entire temperature
range (monotropism) but kinetically stable for at least a year. Freeze-drying of an aqueous solution leads to the amorphous
form. On heating and in moist air amorphous PRCHC exclusively crystallizes to the stable mod. I. PRCHC exemplifies that certain
metastable polymorphic forms are only accessible via a specific solvate, but not via any other crystallization path. Since
no crystallization from 1,4-dioxane was performed in earlier solid-state studies of this compound, PRCHC was to this date
rated as monomorphic.