Minimisation of salicylic acid formation during preparation of aspirin products for analysis by high-performance liquid chromatography

Abstract

The simultaneous separation of aspirin and its degradation product salicylic acid, together with caffeine and paracetamol, can be achieved by reversed-phase high-performance liquid chromatography. The accuracy of measurement of salicylic acid is reduced by conversion of aspirin into salicylic acid during sample preparation. This is a serious limitation when other components of aspirin preparations, such as carbonates, catalyse the conversion or when sample solutions are prepared in advance for use with an autoinjector. A sample solvent containing acetic anhydride, oxalic acid and acetic acid has been found to reduce hydrolysis to about 5% of that of a conventional solvent (methanol).