Abstract

A REVIEW ON THE APPLICATIONS OF THERMAL ANALYSIS.

Jinijith S.*

ABSTRACT

Thermal analysis includes all methods measuring some parameter during the heating of a sample. Differential scanning calorimetry (or differential thermal analysis) where the parameter is heat flow into and out of the sample and thermogravimetry where the parameter is the weight change of the sample are of great value for the pharmaceutical industry. Characterisation of drug substance, excipients, and packaging material: identification, purity, polymorphism, solvation, stability, etc. may be routinely done. Further examples demonstrating the use of these methods for the development of the dosage form are given: choice of the salt form, phase-diagrams, drug substance-excipient interactions, physical changes on processing or during storage, and even analysis of the dosage form. Thermal analysis methods are well- established techniques in research laboratories of pharmaceutical industry. The robustness and sensitivity of instrumentation, the introduction of automation and of reliable software according to the industrial needs widened considerably the areas of applications in the last decade. Calibration of instruments and validation of results follow the state of the art of cGMP as for other analytical techniques. Thermal analysis techniques are especially useful for the study of the behaviour of the poly-phasic systems drug substances and excipients and find a unique place for new delivery systems. Since change of temperature and moisture occur by processing and storage, changes of the solid state may have a considerable effect on activity, toxicity and stability of compounds. Current requirements of the International Conference of Harmonisation for the characterization and the quantitation of polymorphism in new entities re-enforce the position of thermal analysis techniques. This challenging task needs the use of complementary methods. Combined techniques and microcalorimetry demonstrate their advantages. This article reviews the current use of thermal analysis and combined techniques in research and development and in production. The advantage of commercially coupled techniques to thermogravimetry is emphasized with some examples.

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