Direct stereoselective assay of fluoxetine and norfluoxetine enantiomers in human plasma or serum by two-dimensional gas-liquid chromatography with nitrogen-phosphorus selective detection.
A method was developed and validated for the direct enantioselective assay of fluoxetine and norfluoxetine in human plasma or serum by two-dimensional capillary gas-liquid chromatography (GC). A Rtx-1 fused-silica capillary (15 mx0.25 mm I.D., 1.0 micrometer film thickness) and a hydrodex-beta-6-TBDM fused-silica capillary (25 mx0.25 mm I.D., 0.25 micrometer film thickness) were used. A three-step liquid-liquid extraction was used for sample preparation with fluvoxamine and nisoxetine as internal standards. The method provided linear calibration between about 5 and 250 ng/ml for (R)- and (S)-fluoxetine as well as 15 and 250 ng/ml for (R)- and (S)-norfluoxetine. The limits of detection were about 1.5 and 6 ng/ml, respectively. Intra-day precision (coefficient of variation) was estimated as being between 5.4 and 12.7% at plasma levels of 25, 100 and 200 ng/ml for the four enantiomers. Inter-day precision was between 5.3 and 9.1% at 100 ng/ml. The enantioselective separation of some racemic psychopharmaceuticals was tested with various cyclodextrin GC-capillaries. Advantages and disadvantages of direct enantioselective GC are discussed for the assay of racemic psychopharmaceuticals. Samples from a patient who was treated with racemic fluoxetine were measured. In agreement with literature, plasma levels of the (R)-enantiomers of fluoxetine and norfluoxetine were considerably decreased in comparison to the (S)-enantiomers.
Ulrich
Sven
S
Institute of Clinical Pharmacology, University Hospital Magdeburg, Leipziger Strasse 44, D-39120, Magdeburg, Germany. sven.ulrich@medizin.uni-magdeburg.de
D018687:Antidepressive Agents, Second-Generation / Q000097:blood*; D002849:Chromatography, Gas / Q000379:methods*; D005473:Fluoxetine / Q000031:analogs & derivatives* / Q000097:blood*; D006801:Humans; D009584:Nitrogen; D010758:Phosphorus; D015203:Reproducibility of Results; D013237:Stereoisomerism
D018687:Antidepressive Agents, Second-Generation; D005473:Fluoxetine; D010758:Phosphorus; C036139:norfluoxetine; D009584:Nitrogen