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Journal of Thermal Analysis and Calorimetry
Authors: Vittorio Berbenni, Chiara Milanese, Giovanna Bruni, Alessandro Girella, and Amedeo Marini

Abstract

Simultaneous TG–DSC measurements have been used to study the solid state reaction in the system SnC2O4–4MgCO3·Mg(OH)2·xH2O (Sn:Mg = 0.5). The results obtained with physically prepared mixture and with mixture mechanically activated by high-energy milling are compared. Synthesis of the compound Mg2SnO4 has been attempted starting from both type of mixture: Mg2SnO4 forms by annealing the activated mixture at temperatures between 850 and 1,000 °C while it can hardly be obtained from physical mixtures even by thermal treatment at temperature as high as 1,300–1,350 °C. Mg2SnO4 prepared by annealing the activated mixture has been characterized by diffuse reflectance FT-IR spectroscopy, modulated temperature differential scanning calorimetry, scanning electron microscopy, and specific surface area measurements (B.E.T. method).

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Abstract

Copper Ferrite has been prepared by solid state synthesis of milled mixtures of copper basic carbonate [Cu(OH)2 · CuCO3] and iron (II) oxalate dihydrate [FeC2O4 · 2H2O]. The reaction mechanism has been studied by simultaneous TG/DSC analysis: the different steps of the mass loss process have been individuated along with the relevant enthalpy terms starting from both physical and mechanically activated mixtures. CuFe2O4 has been synthesized by annealing the mechanically activated mixture at 750–800 °C while no pure CuFe2O4 is obtained by annealing the physical mixture at temperatures as high as 1100 °C. CuFe2O4 has been characterized as concerns the molar het capacity, the tetragonal–cubic transition enthalpy and the Curie point.

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Abstract  

This work is part of a systematic study undertaken to find and optimize a general method of detecting the drug-excipient interactions, with the aim of predicting rapidly and inexpensively the long term stability of a pharmaceutical product and speed up its marketing. Here, in particular, the compatibility of haloperidol with several excipients (PVP, magnesium stearate and α-lactose) in binary and ternary mixtures, both as prepared and ball-milled, has been assessed by thermal methods, electron microscopy, IR spectroscopy and X-ray diffraction. The differences between the experimental behaviour of the systems and that expected as weighted average of similarly treated pure components are interaction indicators. The DSC has proven to be, among the selected analytical techniques, the most sensitive and specific in assessing the compatibility. A strong interaction has been observed between PVP and haloperidol. It is favoured by the mechanical stress and is more evident in the composition 20:80. On the contrary, α-lactose and magnesium stearate were found to be compatible with the drug.

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Journal of Thermal Analysis and Calorimetry
Authors: Giovanna Bruni, Vittorio Berbenni, Franco Sartor, Chiara Milanese, Alessandro Girella, Dionigio Franchi, and Amedeo Marini

Abstract

In this work, thermoanalytical, diffractometry, and microscopy measurements have been performed in order to characterize the effect of high energy milling on a drug active in the migraine prophylaxis and smoke cessation. We can assert that the mechanical treatment induces only a partial amorphisation of the solid phase, in particular it reduces the crystal order by producing lattice defects which propagate from the surface to the bulk crystal. For this reason, the DSC is able to detect the presence of ordered solid, while the powder X-ray diffractometry, because of its low penetration depth, does not reach the crystalline core of the particles.

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Journal of Thermal Analysis and Calorimetry
Authors: Giovanna Bruni, C. Milanese, G. Bellazzi, V. Berbenni, P. Cofrancesco, A. Marini, and M. Villa

Abstract  

The processes of production of drugs and dosage forms in the solid state often cause unwanted transformation of portions of the substances into amorphous state, with significant changes of properties such as stability and bio-availability. When this amorphous fraction is of the order of a few percent, it usually goes unnoticed, but it should be accurately determined within a quality control system. In this work, we consider a model drug, perphenazine, where partial amorphisation may be induced by standard mechanical treatments. We show that Differential Scanning Calorimetry (DSC) leads to consistent estimations of the amorphous fractions induced by the treatment. Furthermore, DSC also yields the expected amounts of amorphous perphenazine when analysing known mixtures of perfectly crystalline samples (untreated) and partially amorphous samples (treated). We show that even amorphous fractions of the order of 1% are accurately estimated by our method.

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Journal of Thermal Analysis and Calorimetry
Authors: Giovanna Bruni, Franco Sartor, Vittorio Berbenni, Chiara Milanese, Mariarosa Maietta, Dionigio Franchi, and Amedeo Marini

Abstract

In this study, we present a full thermal characterization of antidepressant paroxetine and summarize the results for another drug which treats depression: GW597599B. The main aim is to analyze how the thermodynamic and structural properties of these compounds are modified when the two drugs are mixed in the solid state. We begin by putting into evidence how dehydration and melting concur in shaping the calorimetric curves of paroxetine under different experimental conditions. Equipped with this knowledge, we are able to interpret the thermal response of the physical mixtures paroxetine:GW597599B, in terms of partial eutectic formation and simple superposition of contribution from the two compounds.

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