Subnanometre size free volumes in amorphous Verapamil hydrochloride: a positron lifetime and PVT study through T(g) in comparison with dielectric relaxation spectroscopy

European Journal of Pharmaceutical Sciences : Official Journal of the European Federation for Pharmaceutical Sciences
Günter DlubekFranz Faupel

Abstract

Positron annihilation lifetime spectroscopy (PALS), a method well established for the study of polymers, is employed to characterize the temperature dependence of the free volume through T(g) in the amorphous pharmaceutical Verapamil hydrochloride. From the PALS spectra analyzed with the routine LifeTime9.0 the size (volume) distribution of local free volumes (subnanometre-size holes), its mean, v(h), and mean dispersion, sigma(h), were calculated. A comparison with the macroscopic volume from PVT-experiments delivered the hole density and the hole free volume fraction and in that way a complete characterization of the free volume microstructure. These data are used in correlation with structural (alpha-) relaxation data from broad-band dielectric spectroscopy in terms of the Cohen-Turnbull free volume model. An extension of this model, distinctions in the free volume behaviour of the glassy and supercooled-liquid state and different ways of extrapolating the equilibrium part of the free volume into the temperature range of the glass are discussed. The potential of the PALS method for the study of pharmaceuticals is briefly reviewed and some recently developed applications (analysis of density fluctuations) are illuminated.

References

Apr 17, 1999·International Journal of Pharmaceutics·C RustichelliG Gamberini
Aug 26, 2003·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·Hajime Tanaka
Sep 2, 2005·Journal of Pharmaceutical Sciences·G P JohariRavi M Shanker
Sep 7, 2005·Journal of Pharmaceutical and Biomedical Analysis·Romána ZelkóKároly Süvegh
Oct 13, 2007·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·J BartosJ Colmenero
Dec 31, 2008·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·Günter DlubekMarian Paluch
Jun 6, 2009·Journal of Pharmaceutical Sciences·Sisir Bhattacharya, Raj Suryanarayanan
Jul 14, 2009·Journal of Pharmaceutical Sciences·K AdrjanowiczR Lunio

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Citations

Feb 13, 2016·Journal of Pharmaceutical Sciences·Hiroshika GoshimaMichael J Pikal
Dec 18, 2016·The Journal of Chemical Physics·F PuosiD Leporini
Jan 20, 2017·Journal of Physics. Condensed Matter : an Institute of Physics Journal·S BerniniD Leporini

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