Detection and determination of salicylic acid impurity in aspirin tablet formulations' by high performance liquid chromatography.

Salicylic acid is a major hydrolytic degradation product of aspirin, responsible especially for gastric irritation during oral aspirin administration. This impurity was investigated in 12 different brands of aspirin formulation readily available in our locality. A simple, rapid and sensitive high performance liquid chromatographic method was adopted for this investigation. The mobile phase was methanol/water (20/80, v/v) adjusted to pH 2.5 with phosphoric acid and was run on a 50 mm reversed-phase column monitored at 240 nm. The limit of detection for salicylic acid was 5 ng. Only three of these formulations showed the presence of salicylic acid impurity and all these contained salicylic acid in excess of the USP 1980 limit of 0.3% salicylic acid per tablet.