Differential scanning calorimetry , theory

Reading M. Hourston DJ. Modulated Temperature Differential Scanning Calorimetry. Theory and Practical Applications in Polymer Characterisation. Dordrecht, Holland Springer, 2006. 

J. H. Flynn. Theory of Differential Scanning Calorimetry—Coupling of Electronic and Thermal Steps. In Analytical Calorimetry, vol. 3 R. S. Porter, J. F. Johnson, Eds. Plenum New York, 1974 17-44. 

Freire E. Differential scanning calorimetry. In Shirley BA, ed. Protein Stability and Folding— Theory and Practice. Totowa, NJ Humana Press, 1995 191-218. 

In most cases, the purity of a pharmaceutical substance is determined by comparison of the reference standard with the known purity assigned. On the other hand, when no reference standard sample is available, the purity is determined by an absolute method in which the calculated result is based on theory and not by a comparative method. Purity established by analytical methods such as phase-solubility analysis or differential scanning calorimetry (DSC) is known as absolute purity (Figs. 3 and 4). 

Figure 2 shows how glass transition temperatures (Tg) obtained by dynamic mechanical spectroscopy (DMS), percent crystallinities obtained by wide angle x-ray scattering (WAXS) or differential scanning calorimetry (DSC), experimental diffusion coefficients, and information on tortuosity obtained by studies of morphology, can be useful in applying both the theory of V D and the model of P D. The Williams-Landel-Ferry (WLF) parameters [18] c % and C2 , which can be determined by DMS, are needed as additional input for the theory of V D. Densities and thermal expansion coefficients are needed as additional input for the model of P D. 

In this paper, a thermodynamic phase transition is studied using Differential Scanning Calorimetry (DSC). This phase transition, which will be described according to the current thermodynamic theories as a first order or a second order one, is recorded on the DSC trace as an anomalous change in the differential power ZP, different from the normal IP variation only due to the heat capacity of the material. This variation, sharp or smooth, will be called the "transition peak". We define the height h of the peak as the distance between the heat capacity trace, or baseline, and the maximum during the course of the phase transition. In the case of a pure second order phase transition, this height is the diffe-... 

---