Comparison of liquid chromatography with fluorescence detection to liquid chromatography–mass spectrometry for the determination of fluoxetine and norfluoxetine in human plasma

A comparison study on fluoxetine (FL) and norfluoxetine (NORFL) quantitation in human plasma was carried out between the recently developed liquid chromatographic method with fluorescence detection (LC–FLD) and an earlier established liquid chromatography–mass spectrometry (LC–MS) laboratory procedure. Comparative method evaluation was based on the analysis of plasma samples obtained from Parkinsonian patients receiving 20 mg of FL per day. The LC–FLD method involves a two-step liquid extraction procedure without any derivatization, followed by direct chromatography on a Zorbax C8 reversed-phase column. The analytical results are discussed in terms of the method validation and the corresponding experimental protocol (r ≥ 0.998; CV < 9%; LOQ 20 μg/l). There was good correlation between FL, as well as NORFL, plasma levels as determined by the LC–MS and LC–FLD techniques (r = 0.9597, N = 16 and r = 0.9852, N = 14 for FL and NORFL, respectively). The results confirm that direct FL/NORFL fluorimetric determination is acceptable for routine use in pharmacokinetic and clinical studies.