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A second-derivative spectrophotometric method for the determination of naproxen in the absence or presence of its 6-desmethyl metabolite in human plasma is described. The method consists of direct extraction of the non-ionized form of the drug with pure diethyl ether and determination of the naproxen by measuring the peak amplitude (mm) in the second-order derivative spectrum at a wavelength of 328.2 nm. The efficiency of the extraction procedure expressed by the absolute recovery was 94.6 +/- 0.7% (mean +/- s) for the concentration range tested, and the limit of quantification attained according to the IUPAC definition was 2.42 mg l-1. The linear dynamic range for naproxen was 5.0-100.0 mg l-1, the correlation coefficient for the calibration graphs was excellent, r = 0.99993 (n = 6), the precision (Sr) was better than 4.58% and the accuracy was satisfactory (Er < 2.32%). The results obtained by the proposed method were in good agreement with those found by an HPLC method.

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The goal of this work is to investigate the direct chromatographic separation of the enantiomers of fluoxetine and its active metabolite norfluoxetine. The liquid chromatographic retention behavior of these enantiomers on a P-cyclodextrin bonded-phase column was investigated with respect to mobile phase composition, pH, ionic strength, and solvent selectivity. Relationships were established between these factors and the three most important chromatographic parameters: retention time, resolution, and selectivity. Most of the evidence suggests that the unique selectivity of this column isdue to inclusion complex formation, which provides the physical basis for enantiomeric resolution. After these studies a set of optimum chromatographic conditions was chosen for the simultaneous separation/ determination of a mixture of the four enantiomers using fluorescence detector. Since FL is marketed as a racemic mixture, the pharmacology, metabolism, and pharmacokinetics of the enantiomers of FL and its metabolites have important clinical implications. The enantiomers of FL exhibit the biochemistry and pharmacology in vitro and in vivo of selective 5-HT uptake inhibitors with about equal potencies.However, many differences have been reported in the literature with regard to their relative pharmacological potencies. (+)-(S)-FL appears to be slightly more potent than (-)-(R)-FL in blocking 5-HT uptake in vivo or preventingp-chloroamphetamine induced depletion of brain 5-HT.4 (+)-(3-FL was also seen more potent when the two enantiomers were compared for their abilities to lower food intake in meal-fed rats and in 2-deoxyglucose-induced hyperphagic rats. serotonin uptake activity of (+)-(S)-NR was 16-fold greater in vitro and 20-fold greater in vivo than that of (-)-R-NR.7*8 Therefore, the difference in the duration of action between the isomers of FL can be partially explained on the basis of conversion of (-)-(R)-FL to the relatively inactive (-)-(R)-NR.A limited number of analytical methods have been reported for the assay of FL and NR in biological Only one of these methods7 was capable of successfully separating and quantitating the enantiomers of FL and NR using an indirect chromatographic procedure (chiral derivatization). The present work describes a simple, sensitive, and direct chromatographic method for the determination of the enantiomers of FL and NR using fluorescence detection.Optical resolution by direct chromatography is possible through reversible diastereomeric association between a chiral selector introduced into a column and the solute enantiomers. For the application of cyclodextrins (CDs) in this stereoselective process, two different approaches have been recently designed the use of chemically bonded cyclodextrins (CDs) silica stationary phased3 and the application of CDs as mobile phase additives in RP-HPLC. l4 In this paper the use of a P-cyclodextrin bonded stationary phase has been used to investigate the resolution of the enantiomers of fluoxetine and