Local Thermal Analysis by Structural Characterization (TASC)
Thermal analysis by structural characterization (TASC) is a new thermal technique that is based on image analysis combined with hot-stage microscopy (HSM, also called thermomicroscopy). The image analysis algorithm is sensitive to any change in structure as seen by digital optical microscopy. A key feature of the algorithm is that it accounts for any sample movement. Due to thermal expansion of the sample or the sample chamber, there is, at high magnification, usually some sample displacement and this needs to be removed, so the measurement is purely one of structural change. HSM has a variety of uses but struggles with opaque samples (such as filled samples) and cannot routinely detect glass transitions. TASC, when used with an imposed structure such as an indentation, can routinely measure glass transition temperatures because, when the sample softens, the indentation disappears. This is true even when analyzing opaque samples. TASC can also be used to measure melting temperatures, transitions in small (microgram) samples, dissolution behavior, and heterogeneity.
KeywordsMetastable Form Crystalline Drug Thermal Dissolution Metastable Polymorph Drug Melting
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