The effect on the stability of the isomers of aminosalicylic acid of formation of their sodium salts has been studied by use
of differential scanning calorimetry and thermogravimetry, coupled with evolved gas analysis by Fourier transform infrared
spectroscopy. X-ray powder diffraction and infrared spectroscopy provided complementary information. The DSC curves for the
sodium salts of all of the isomers showed complex dehydration/decomposition endotherms. From the initial mass losses of the
TG curves, the amounts of water per mole of salt were estimated as 0.5, 2.4 and 1.4 moles for the sodium salts of 3-aminosalicylic
acid, 4-aminosalicylic acid and 5-aminosalicylic acid, respectively. TG-FTIR results for the sodium salt of 3-aminosalicylic
acid showed the evolution of carbon dioxide in three stages: below 150C, between 200 and 300C and continuous formation up
to 500C. This behaviour differs from that of 3-aminosalicylic acid itself, which forms CO2 between 225 and 290C. For the sodium salt of 4-aminosalicylic acid, the formation of carbon dioxide starts from 250C and
is still being formed at about 650C. 4-aminosalicylic acid decarboxylates above 150C. 5-aminosalicylic acid and its sodium
salt showed no evolution of carbon dioxide below 600C.
Nifedipine complexes with β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), 2-hydroxypropyl-β-cyclodextrin (2HP-β-CD), randomly
methylated-β-cyclodextrin (RM-β-CD) and heptakis(2,6-O-dimethyl)-β-cyclodextrin (DM-β-CD) have been prepared by both kneading and heating methods and their behaviour studied by
differential scanning calorimetry (DSC), diffuse reflectance mid-infrared spectroscopy (FTIR) and X-ray diffractometry (XRD).
DSC revealed the nifedipine melting endotherm with onset at approximately 171°C for the kneaded mixtures with β-CD, γ-CD and
2HP-β-CD, thus confirming the presence of nifedipine in the crystalline state, while some decrease in crystallinity was observed
in the DM-β-CD kneaded mixture. With RM-β-CD, however, broadening and shifting of the nifedipine endotherm and reduction in
its intensity suggested that the kneading could have produced an amorphous inclusion complex. These differing extents of interaction
of nifedipine with the cyclodextrins were confirmed by FTIR and XRD studies.
The thermal behaviour of benzoic and salicylic acids is compared with the behaviour of 1:1 molar ratio physical and kneaded
mixtures of these acids with each of three different cyclodextrins (b-, hydroxypropyl-b-, and g-cyclodextrin). Differential
scanning calorimetry and thermogravimetry coupled with evolved gas analysis by Fourier transform infrared spectroscopy were
used for the thermal studies and X-ray powder diffraction and infrared spectroscopy provided complementary information. Thermal
studies of benzoic acid with the cyclodextrins showed significant interactions in both physical and kneaded mixtures of benzoic
acid/b-cyclodextrin and benzoic acid/hydroxypropyl-b-cyclodextrin. Interactions in the kneaded benzoic acid/g-cyclodextrin
mixtures were the most extensive as might be expected for the cyclodextrin with the largest molecular cavity. The results
for the salicylic acid/b-cyclodextrin and salicylic acid/hydroxypropyl-b-cyclodextrin mixtures were similar to those for benzoic
acid/b-cyclodextrin and benzoic acid/hydroxypropyl-b-cyclodextrin. Again, the kneaded salicylic acid/g-cyclodextrin mixture
showed the most interaction.
The theoretical background relevant to the use of pyrometry in the study of fast processes involving rapid temperature changes initially solid samples is outlined. Pyrometers of various kinds are described briefly and their applications in the study of pyrotechnic reactions, schock-wave research, thermal imaging and the measurement of thermophysical properties are reviewed.
The thermal behaviour of Ba[Cu(C2O4)2(H2O)]·5H2O in N2 and in O2 has been examined using thermogravimetry (TG) and differential scanning calorimetry (DSC). The dehydration starts at relatively
low temperatures (about 80°C), but continues until the onset of the decomposition (about 280°C). The decomposition takes place
in two major stages (onsets 280 and 390°C). The mass of the intermediate after the first stage corresponded to the formation
of barium oxalate and copper metal and, after the second stage, to the formation of barium carbonate and copper metal. The
enthalpy for the dehydration was found to be 311±30 kJ mol−1 (or 52±5 kJ (mol of H2O)−1). The overall enthalpy change for the decomposition of Ba[Cu(C2O4)2] in N2 was estimated from the combined area of the peaks of the DSC curve as −347 kJ mol−1. The kinetics of the thermal dehydration and decomposition were studied using isothermal TG. The dehydration was strongly
deceleratory and the α-time curves could be described by the three dimensional diffusion (D3) model. The values of the activation
energy and the pre-exponential factor for the dehydration were 125±4 kJ mol−1 and (1.38±0.08)×1015 min−1, respectively. The decomposition was complex, consisting of at least two concurrent processes. The decomposition was analysed
in terms of two overlapping deceleratory processes. One process was fast and could be described by the contracting-geometry
model withn=5. The other process was slow and could also be described by the contracting-geometry model, but withn=2.
The values ofEa andA were 206±23 kJ mol−1 and (2.2±0.5)×1019 min−1, respectively, for the fast process, and 259±37 kJ mol−1 and (6.3±1.8)×1023 min−1, respectively, for the slow process.
Triprolidine hydrochloride, C19H22N2HClH2O (TPH) is a well-known antihistamine drug, which is reported as being photosensitive. Solid-state photostability studies
of TPH were undertaken by irradiating TPH and its binary mixtures with β-cyclodextrin (BCD) and glucose, using an Atlas Suntest
CPS+ irradiation chamber and conditions according to the guidelines of the International Committee on Harmonization (ICH). HPLC
analysis was used to determine the extent of photodegradation. XRD results showed that changes in the TPH crystal structure
had occurred during irradiation and that these changes increased with the time of irradiation. Although the potential for
isomerization under the influence of UV-light to the pharmaceutically inactive Z-isomer exists, results have proved that this
transformation for solid-state TPH would require more extreme light conditions. The results of this study thus illustrate
the general light stability of TPH in the solid-state.