Brandon R A, Eadie M J, Smith M T
Ther Drug Monit. 1985;7(2):216-21. doi: 10.1097/00007691-198506000-00014.
An original, highly sensitive and specific high performance liquid chromatographic method has been developed for the measurement of aspirin and salicylate in plasma. Minimum concentrations of 10 micrograms/L (aspirin) and 0.5 mg/L (salicylate) can be measured using 1 ml of plasma. After collection, plasma is first treated with physostigmine sulfate to inhibit enzymatic hydrolysis of aspirin to salicylate. Maximal recovery is achieved using an acid extraction into anhydrous diethyl ether with a subsequent drying-down step in an iced water bath. Aspirin and salicylate are separated by elution with a mixture of methanol, 1-butanol, orthophosphoric acid, and water on a reversed-phase octadecyl silane column at 47 degrees C and detected at 234 nm by ultraviolet absorption. Quantitation is achieved using the peak height ratio of aspirin and salicylate to internal standard (m-anisic acid). The assay has been used for the study of simultaneous aspirin and salicylate pharmacokinetics after a single oral dose of 100 mg soluble glycinated aspirin for platelet antiaggregatory therapy in six subjects, one of whom was also studied after receiving a 600 mg dose.
