Determination of drug stability in aspirin tablet formulations by high-pressure liquid chromatography.

Salicylic acid and aspirin were resolved from the other salicylates in thermally degraded multicomponent tablets and determined quantitatively. The analytical method involved wetting the powdered tablet with acetic acid and diluting with chloroform to extract the drug components. Automated high-pressure liquid chromatographic analyses of filtered extracts were performed on a silica column with a mobile phase of acetic acid in heptane. The method was capable of resolving the major thermally induced transformation products in tablet formulations. It was sensitive to approximately 0.1 mg of salicylic acid/tablet. Good agreement with the compendial method for free salicylic acid was obtained.