Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: A. Gazzaniga x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract

A hydrated form of theophylline-7-acetic acid obtained by recrystallization from water is described and characterized in terms of thermal properties, physical stability with respect to relative humidity and dehydration kinetics. The hydrate resulted to be stable at ambient conditions. Fitting of experimental dehydration data to solid state reaction equations suggests a three dimensional phase boundary reaction proceeding from the surface of the crystal inward along three dimensions. The relevant activation energy calculated from the Arrhenius plot is 173 kJ/mol.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: F. Giordano, A. Rossi, R. Bettini, A. Savioli, A. Gazzaniga, and Cs. Novák

Abstract  

The thermal behavior of binary mixtures of paracetamol and a polymeric excipient (microcrystalline cellulose, hydroxypropylmethylcellulose and cross-linked poly(vinylpyrrolidone)) was investigated. The physical mixtures, ranging from 50 to 90% by mass of drug, were submitted to a heating-cooling-heating program in the 35–180C temperature range. Solid-state analysis was performed by means of differential scanning calorimetry (DSC), hot stage microscopy (HSM), micro-Fourier transformed infrared spectroscopy (MFTIR), and scanning electron microscopy (SEM). The polymeric excipients were found to address in a reproducible manner the recrystallization of molten paracetamol within the binary mixture into Form II or Form III. The degree of crystallinity of paracetamol in the binary mixtures, evaluated from fusion enthalpies during the first and second heating scans, was influenced by the composition of the mixture, the nature of the excipient and the thermal history. In particular, DSC on mixtures with cross-linked poly(vinylpyrrolidone) and hydroxypropylmethylcellulose with drug contents below 65 and75%, respectively, evidenced the presence only of amorphous paracetamol after the cooling phase. Microcrystalline cellulose was very effective in directing the recrystallization of molten paracetamol as Form II.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: F. Giordano, A. Rossi, I. Pasquali, R. Bettini, E. Frigo, A. Gazzaniga, M. Sangalli, V. Mileo, and S. Catinella

Abstract  

The thermal behaviour of Diclofenac was investigated using Differential Scanning Calorimetry, Hot Stage Microscopy, and Thermogravimetric Analysis. A discrepancy was observed between the melting point values recorded under dynamic flow of either dry nitrogen (180C) or air (160C). By means of High Performance Liquid Chromatography/Mass Spectrometric analyses, it has been possible to ascribe this difference in melting points to the formation of three degradation products as a result of intramolecular cyclization and condensation reactions during the heating process in an oxidative atmosphere.

Restricted access