Fluorous derivatization and fluorous-phase separation for fluorometric determination of naproxen and felbinac in human plasma

Fluorous derivatization followed by fluorous-phase liquid chromatographic (LC) separation exploits the affinity between perfluoroalkyl compounds for highly selective and quantitative isolation of various analytes. However, the applicability of this technique as a simple pretreatment for fluorometric determination in clinical settings has not been fully explored. Here we show the applicability of this technique to the clinical determination of non-steroidal anti-inflammatory drugs (NSAIDs) in human plasma. Naproxen and felbinac, widely used native-fluorescent NSAIDs with a carboxyl group, can have toxic effects at acute doses, and were therefore chosen as representative NSAIDs. Samples were precolumn derivatized with a non-fluorescent fluorous amine, which allowed highly selective retention of only derivatized substances in the fluorous LC column. Thus, subsequently, only the retained fluorous-labeled and fluorescent analytes were detected fluorometrically at appropriate retention times. The detection limits for these two drugs were less than 11 fmol on column. Correlation curves were liner over the range of 0.04–10 and 5–250 nmol/mL plasma for both two drugs (r > 0.999) with good repeatability. Thus, this method offers a simple, sensitive, and selective solution for determination of NSAIDs in clinical settings.