DSC purity analysis of substances in drugs or foodstuffs is an important issue. In general, substances with significant amounts of impurity may produce unexpected reactions, lose their efficiency, or create toxic compounds. In the worst case, even just a few percent of an impurity could be toxic or even lethal.
Definition of Purity
According to the International Union of Pure and Applied Chemistry,
“A sample is sufficiently pure when the amount of each of the impurities which may interfere with the specific purpose for which the sample is required is so low that their combined effect is negligible within the desired limits of accuracy”.
The amount and nature of impurities in a substance is usually expressed as a percentage or in mole percent.
DSC Purity Analysis
Purity determination by DSC is based on the thermodynamics of an ideal eutectic system. This can be shown in the form of a phase diagram, explained in this webinar. Many mixtures of organic substances exhibit this type of behavior.