Differential thermal analysis methodology

In a manner similar to that just described for differential thermal analysis, DSC can be used to obtain useful and characteristic thermal and melting point data for crystal polymorphs or solvate species. This information is of great importance to the pharmaceutical industry since many compounds can crystallize in more than one structural modification, and the FDA is vitally concerned with this possibility. Although the primary means of polymorph or solvate characterization s centered around x-ray diffraction methodology, in suitable situations thermal analysis can be used to advantage. 

These parameters need to be considered for reactions that go towards the intended completion as well as for possible upsets (see section C). Measuring methodologies for determining characteristic material property values (Stoffkenngrofcen), e.g., differential thermal analysis ("DTA"), calorimetry, and adiabatic experiments, and their possible use and applications are given in the literature /1, 2, 3, 41. 

Methodology for studying the polymorphism of fats, among which thermal analysis, most typically, differential scanning calorimetry (DSC), X-ray diffraction (XRD), neutron diffraction, infrared absorption spectroscopy, and nuclear magnetic resonance (NMR), are briefly mentioned here. 

When one polymorph can be thermally converted to another, differential scanning calorimetry (DSC) analysis cannot be used to deduce the heat of transition between the two forms, and so solution calorimetry represents an alternative methodology. This situation was encountered when evaluating the polymorphs of losartan [140], Enthalpies of transition were obtained in water (A(A//sol) = 1.723 kcal/mol) and in A A-dimethylformarnide (A(A//S0 ) = 1.757 kcal/mol), with the equivalence in results demonstrating the quality of the results. Although enthalpy does not indicate stability, the authors deduced from solution calorimetry that form I was more stable than form II at ambient temperature. 

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