DETERMINATION OF ANTIPYRINE METABOLITES IN HUMAN PLASMA BY SOLID-PHASE EXTRACTION AND MICELLAR LIQUID-CHROMATOGRAPHY

A rapid solid-phase extraction (SPE) procedure was developed for the q uantitative isolation of three important antipyrine (dipyrone) metabol ites from human plasma: 4-formylaminoantipyrine (FAA), 4-aminoantipyri ne (AA) and 4-methylaminoantipyrine (MAA). Separation and quantitation were performed using micellar liquid chromatography (MLC) with a 0.1 mol l(-1) sodium dodecyl sulfate (SDS)-2.5% pentanol mobile phase and UV detection at 262 nm. The metabolites were well resolved in less tha n 5 min using an octadecyl silica-bonded stationary phase. The extract ion procedure involved passing 0.3 ml of plasma sample through a dispo sable SPE cartridge packed with C-18 bonded porous silica. The adsorbe d metabolites were removed from the cartridge with methanol. The eluen t was evaporated to dryness and the residue was reconstituted with mob ile phase and injected into the chromatographic system. The cartridge blank interferent peaks, the effects on reproducibility of sample load ing in the cartridge and volume needed for desorption of metabolites w ere evaluated. The concentration of metabolites ranged between 2.4 and 4 mu g ml(-1). The present procedure yields recoveries for the three metabolites ranging from 93 to 100%. The relative standard deviation ( s(r)) ranged between 1.2 and 13.6%. Limits of detection (LODs) were 10 .5, 11.5 and 17.0 ng ml(-1) for FAA, AA and MAA, respectively.