Determination of aspirin and salicylic acid in uremic patients' plasma using reversed-phase high-performance liquid chromatography.

A simple, rapid, and sensitive method for the determination of aspirin and salicylic acid in plasma of uremic patients is reported. After extraction with hexane, aspirin (ASA) and salicylic acid (SA) were quantified by high-performance liquid chromatography (HPLC) with ultraviolet detection at 229 nm. ASA and SA concentrations and peak-height ratios were linearly related up to 20 micrograms/ml. The lower limit of sensitivity was 0.1 microgram/ml for both compounds. The average recoveries of aspirin and salicylic acid were 27 and 54%, respectively. This procedure offers better performance than do previously described methods. The sample clean-up allows quantitation of a low concentration of aspirin in uremic patients' plasma, commonly rich in interfering endogenous substances.