Unusual chromatographic enantioseparation behavior of naproxen on an immobilized polysaccharide-based chiral stationary phase.
ABSTRACT Enantioseparation of naproxen was performed on an immobilized polysaccharide-based chiral stationary phase (CSP), Chiralpak IA, in the normal-phase mode. The effects of polar alcohol modifier in mobile phase and column temperature on retention, enantioseparation, and elution order were investigated. Two unusual phenomena were observed. One was solvent-induced reversal of elution order for the two enantiomers. Not only the type but also the content of polar alcohol modifier could induce the reversal. Another uncommon phenomenon was peak deformation under some chromatographic conditions.
- Journal of Liquid Chromatography & Related Technologies 11/2013; 37(3):433-445. · 0.64 Impact Factor
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ABSTRACT: This work reports a high-performance liquid chromatography normal-phase methodology to elucidate enantiomers of naphthalene derivatives, evaluated as melatoninergic agonists. For this purpose four different polysaccharide based chiral stationary phases were evaluated, namely Chiralcel OD-H (cellulose tris-3,5-dimethylphenylcarbamate), Chiralcel OJ (cellulose tris-methylbenzoate), Chiralpak AD (amylose tris-3,5-dimethylphenylcarbamate) and Chiralpak AS (amylose tris-(S)-1-phenylethylcarbamate) with different alcoholic modifiers on different amounts in n-heptane. A temperature study was carried out, between 20 and 40 °C and the apparent thermodynamic parameters were calculated thanks to the Van't Hoff linearization. For all compounds (except 3), ΔΔH° and ΔΔS° exhibited positive values ranging from 791.2 to 9999.3 J/mol and from 3.9 to 37.8 J/K/mol respectively, indicating entropically driven separations. Optimized conditions led to goof resolution of 2.37 for compound 1 on Chiralpak AS, with heptane–2-propanol 90:10 (v/v), at a temperature of 30 °C. Then they were transposed to the preparative scale for compound 1, generating 22 mg of each enantiomer with an 80% yield. The limits of detection and of quantification were determined to allow the calculation of the enantiomeric excess. They were found with very low values, equal to 0.32 and 1.05 µM and 0.33 and 1.11 µM, respectively, for peaks 1 and 2 of compound 1. Copyright © 2014 John Wiley & Sons, Ltd.Biomedical Chromatography 09/2014; · 1.95 Impact Factor
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ABSTRACT: Commercial (S)-naproxen was racemized under strong basic condition. After checking the peak position of (R)- and (S)-naproxen by analysis the recemized naproxen, optical purity of 19 commercialized naproxens sold in 2013 in Korea were examined by chiral HPLC. The Chiralcel OD-H column, ChiralHyun-LE(S)-1 column and LUX-Cellulose-1 column were used as chiral stationary phases and the mixed eluent of hexane:isopropanol:acetic acid as 100:1:0.1 was used as a mobile phase with a flow rate of 1.0 mL/min. Each data was obtained from an average value of at least three different experiments for each sample and the relative standard deviation of them appeared very small. The average optical purity values obtained from three different chiral columns were very similar and the total average optical purity value (99.32%) of nineteen commercialized naproxens used in this study were larger than those of three years ago (98.17%).Journal of the Korean Chemical Society 04/2014; 58(2).