SIMULTANEOUS LIQUID-CHROMATOGRAPHIC QUANTITATION OF SALICYCLIC ACID, SALICYLURIC ACID, AND GENTISIC ACID IN URINE

Abstract

A specific and sensitive method for the determination of salicylic acid, salicyluric acid and gentisic acid in urine was developed. Any proteins present are precipitated with methyl cyanide. After centrifugation, an aliquot of the supernate is directly injected into an octadecyl silane reversed-phase chromatographic column, then eluted with a mixture of water, butanol, acetic acid and sodium sulfate, and quantitated at 313 nm by UV detection according to peak-height ratios (with internal standard, o-methoxybenzoic acid) or peak heights (no internal standard). The method allows estimates within 25 min. Sensitivity was 0.2 mg/l for gentisic acid, and 0.5 mg/l for salicyluric and salicylic acid (20 .mu.l injection volume); response was linear with concentration to at least 2.000 g/l for salicylic acid and metabolites. Analytical recovery of salicylic acid and metabolites from urine is complete. Intraassay precision (coefficient of variation) is 5.52% at 7.5 mg/l for salicylic acid, 5.01% at 9.33 mg/l for salicyluric acid and 3.07 at 7.96 mg/l for gentisic acid. Interassay precision is 7.32% at 7.51 mg/l for salicylic acid, 5.52% at 8.58 mg/l for salicyluric acid, and 3.97% at 8.32 mg/l for gentisic acid. No significant interference in urine from patients being treated with various drugs other than aspirin was seen.