Differentiating nonaqueous titration of salicylic acid and acetylsalicylic acid combination

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.

Simultaneous determination of aspirin and salicylic acid in bulk aspirin and in plain, buffered, and enteric-coated tablets by high-pressure liquid chromatography with UV and fluorescence detectors

A quantitative high-pressure liquid chromatographic method that uses a reversed-phase column coupled to UV and fluorescence detectors was developed to determine aspirin and salicylic acid in bulk aspirin and in plain, buffered, and enteric-coated tablets. The aspirin was dissolved, filtered, and injected into the chromatograph. The UV absorbance of aspirin was determined at 254 nm, and the fluorescence of salicylic acid was measured at 425 nm. Excipients and impurities did not interfere. Recoveries of 100% were obtained for aspirin and salicylic acid from simulated tablet formulations. Results obtained by the USP XIX procedure and the proposed method were compared. The coefficient of variation for the aspirin analysis was 0.59%; for salicylic acid, it was 1.69%. The rate of hydrolysis of aspirin to salicylic acid in the solvents used was < 0.05%/hr.

Determination of salicylic acid and aspirin in multicomponent tablets by liquid chromatography on a nonionic resin

Aspirin and free salicylic acid were determined in combinations containing caffeine, phenacetin, salicylamide, and acetaminophen by liquid chromatography on poly(methyl methacrylate) resin. Precision and accuracy were +/- 2% for salicylic acid, the latter at levels corresponding to 0.02% of the aspirin content.