Paired-ion high-performance liquid chromatographic assay for sulfinpyrazone in plasma

A specific and sensitive liquid chromatographic method is reported for the assay of sulfinpyrazone in plasma utilizing ion pairing between the tetrabutylammonium cation and the sulfinpyrazone anion. The method is rapid in that conventional extraction procedures are avoided in favor of using disposable cartridges packed with an octade-cylsilane bonded phase as a means of separating the drug from plasma. The samples were chromatographed on a C18 reversed-phase column using a mobile phase consisting of 0.005 M tetrabutylammonium phosphate in methanol-water (56:44). The coefficient of variation obtained was 4.5% and the response was linear over a range of 0.2-80 micrograms/ml.