DYNAMIC DSC PURITY ANALYSIS STUDIES OF 2 COMPONENT DOPED SYSTEMS

Up to the present time, the accuracy and precision of dynamic DSC purity analysis measurements have been tested by using simple binary systems as models. For the most part, pure organic substances have served as host and eutectic-forming low level dopant. As a first step in considering whether the DSC method can be applied to multicomponent impure substances, the simple ternary model system, phenacetin doped with benzamide and p-aminobenzoic acid, has been studied. Separately, the two dopants form well defined eutectics with the host melting at 370 K (benzamide dopant) and 385 K (p-aminobenzoic acid dopant). When the two dopants are combined, a third eutectic melting at 353 K is produced. Evidence is presented confirming the fact that in the range 100-98.5 mole % purity, the total DSC measured impurity is the sum of the two individual dopant levels, and is independent of their relative proportions. © 1979.