Determination of acetylsalicylic acid and metabolites in biological fluids by high-performance liquid chromatography.

A new method has been developed for the determination of acetylsalicylic acid, salicylic acid, salicyluric acid and gentisic acid in plasma, urine and tissue homogenates by simple extraction with ethyl acetate, evaporation and redissolution and measuring by high-performance liquid chromatography. Linearity, reproducibility and recovery were determined. Experiments were carried out to investigate the decomposition of acetylsalicylic acid in plasma with fluoride at different temperatures. The method has been used for pharmacokinetic experiments and an example is given.