SIMULTANEOUS DETERMINATION OF NAPROXEN AND ITS DESMETHYL METABOLITE IN HUMAN SERUM BY 2ND-DERIVATIVE SYNCHRONOUS FLUORESCENCE SPECTROMETRY

A simple, rapid, sensitive and selective method for the simultaneous d etermination of the non-steroidal anti-inflammatory drug naproxen (NAP ) and its main metabolite the 6-demethylated derivative (DNAP) in huma n serum is described. The method is based on the intrinsic fluorescenc e of both acids in alkaline aqueous solution. The broad-band overlappi ng conventional spectra of both compounds are resolved by means of sec ond-derivative synchronous fluorescence spectrometry, thus obviating t he need for pre-analysis sample separation techniques. NAP and DNAP ar e determined in serum supernatant solution after removal of proteins w ith acetonitrile at pH 11.7. Recoveries from sera spiked with NAP (5-7 0 mu g ml(-1)) and DNAP (0.25-5 mu g ml(-1)) ranged from 95 to 106% (m ean 99.6%) and from 95 to 104% (mean 100.1%), respectively.