Thermoanalytical and spectroscopic characterisation of solid-state retinoic acid.
Thermoanalytical (differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG/FTIR)) and spectroscopic (X-ray diffraction (XRD), ultraviolet-visible (UV-Vis), mass spectrometry (MS) and Fourier transform infrared diffuse reflectance (DRIFT) measurements have been used to characterise solid-state retinoic acid (RA) from a chemico-physical point of view. Between 130 and 160 degrees C, a phase transition takes place that does not correspond to the transition between the known monoclinic and triclinic phases (DSC and XRD evidence). By annealing in air (in the 130-160 degrees C temperature range and for different times), an exothermic oxidative degradation occurs that, depending on the thermal treatment, competes with the mentioned phase transition (TGA evidence). Spectroscopic techniques (UV-Vis, MS and DRIFT) allow one to conclude that the new solid phase is still constituted by retinoic acid with a different orientation of the side chain. Finally, RA does not undergo stable melting: the fragmentation patterns, both in air and in nitrogen, have been examined by TG/FTIR.
Berbenni
V
V
CSGI, Dipartimento di Chimica Fisica, Università di Pavia, Viale Taramelli 16, 27100 Pavia, Italy. berbenni@fisav.unipv.it
Marini
A
A
Bruni
G
G
Cardini
A
A
D000970:Antineoplastic Agents / Q000032:analysis*; D002152:Calorimetry, Differential Scanning; D017550:Spectroscopy, Fourier Transform Infrared; D013678:Technology, Pharmaceutical; D013818:Thermogravimetry; D014212:Tretinoin / Q000032:analysis*; D014961:X-Ray Diffraction
D000970:Antineoplastic Agents; D014212:Tretinoin