Dynamics of Pharmaceutical Amorphous Solids: The Study of Enthalpy Relaxation by Isothermal Microcalorimetry

Prediction of the Onset of Crystallization of Amorphous Sucrose Below the Calorimetric Glass Transition Temperature from Correlations with Mobility

“…Here, the standard deviation is based on only two independent measurements, so it is only considered to be a rough indication of the uncertainty of the measurement. The relaxation times for spray-dried sucrose were significantly higher than those of either freeze-dried sucrose or quenched-cooled sucrose (values reported earlier 20,22 and shown for comparison in Table 2), with the difference increasing with decreasing temperature relaxation time constants were similar for two different samples of spray-dried sucrose. Clearly, processing differences do impact relaxation time.…”

Correlations between Molecular Mobility and Chemical Stability During Storage of Amorphous Pharmaceuticals

“…73 Global mobility, as indicated by t, in amorphous pharmaceuticals at temperatures below T g can be determined from enthalpy relaxation time, which can be measured by conventional DSC, modulated temperature DSC 74,75 and isothermal microcalorimetry. 76,77 The enthalpy relaxation times measured for amorphous indomethacin, PVP and sucrose indicated that significant global mobility may be expected even at temperatures well below T g . 78 The enthalpy relaxation times of amorphous benzodiazepines also indicated that global mobility is significant at temperatures below T g .…”

Review: physical chemistry of solid dispersions

“…[82,[104][105][106][107] The above-discussed relaxation enthalpy study can be performed with isothermal microcalorimetry (TAM) as well. [108] The disadvantage of the KWW method is the fact that to reduce analysis time, glasses are annealed at temperatures that are not far below Tg in order to obtain a sufficiently large recovery endotherm signal. Therefore results are extrapolated from temperatures right below Tg to temperatures far below Tg, which correspond to the actual storage temperatures.…”