Jae Jeong Ryoo

Liquid Chromatographic Enantiomer Separation of N‐Phthaloyl Protected α‐Amino Acids on Coated and Immobilized Chiral Stationary Phases Derived from Polysaccharide Derivatives

Abstract Liquid chromatographic enantiomer separation of N‐phthaloyl (PHT) protected α‐amino acids on several coated and immobilized chiral stationary phases (CSPs) derived from polysaccharide derivatives was performed. The coated CSP of Chiralpak AD showed more or less enantioseparation than the covalently bonded CSP of Chiralpak IA with the same chiral selector of amylose tris(3,5‐dimethylphenylcarbamate). However, the coated Chiralcel OD showed greater enantioseparation than the covalently bonded Chiralpak IB with the same chiral selector of cellulose tris(3,5‐dimethylphenylcarbamate). Among all examined CSPs, Chiralcel OD afforded the greatest performance for enantiomer resolution of N‐PHT α‐amino acids and, therefore, all analytes enantiomers were baseline separated on Chiralcel OD. The chromatographic method developed in this study was usefully applied for determination of the enantiomeric purity of commercially available N‐PHT α‐amino acids analytes.

Simultaneous analysis of anionic, amphoteric, nonionic and cationic surfactant mixtures in shampoo and hair conditioner by RP-HPLC/ELSD and LC/MS

A simple and simultaneous analysis method for four (anionic, amphoteric, nonionic, and cationic) classes of surfactants in shampoo and hair conditioner was newly developed. Analysis of the surfactants was performed using a reversed-phase HPLC (RPLC) combined with evaporative light scattering detection (ELSD) without any pre-treatment. An optimum analysis condition for the resolution of both four main surfactant mixtures used in shampoo and five main surfactants used in hair conditioner could be established under a gradient mobile phase condition with acetonitrile, tetrahydrofuran and water. The detection limits were 2.5-30 microg mL(-1) except for SLES (150 microg mL(-1)), and the calibration curves, i.e. the log-log plots, were linear in the working range of 2.5-5250 microg mL(-1) with R(2) values of above 0.998. The observed precision was less than 5% R.S.D. The elution peaks were identified by a liquid chromatography-mass spectrometer (LC-MS) equipped with an electrospray interface operating in mixed-mode.

Covalently Bonded and Coated Chiral Stationary Phases Derived from Polysaccharide Derivatives for Enantiomer Separation of N‐Fluorenylmethoxycarbonyl α‐Amino Acids with Fluorescence Detection

Abstract Liquid chromatographic comparisons for enantiomer resolution of N‐fluorenylmethoxycarbonyl (FMOC) α‐amino acids with fluorescence detection were made on covalently bonded type chiral stationary phases (CSPs) (Chiralpak IA and Chiralpak IB) and coated type CSPs (Chiralpak AD and Chiralcel OD) derived from polysaccharide derivatives of the same chiral selectors. This is the first study reported of enantiomer resolution with fluorescence detection on covalently bonded type CSPs, Chiralpak IA and Chiralpak IB. In general, covalently bonded type CSPs (Chiralpak IA and Chiralpak IB) showed lower enantioseparation than coated type CSPs (Chiralpak AD and Chiralcel OD) for enantiomer resolution of these analytes, respectively. Owing to higher sensitivity and broader solvent compatibility in fluorescence detection on Chiralpak IA and Chiralpak IB than in UV detection, however, this analytical method is expected to enlarge their application of enantiomer resolution, such as an online HPLC monitoring of asymmetric synthesis.

Enantioseparation of racemic N-acylarylalkylamines on various amino alcohol derived π-acidic chiral stationary phases

Five tau-acidic chiral stationary phases (CSPs), CSP 4, CSP 5, CSP 6, CSP 7 and CSP 8, were prepared by connecting the N-(3,5-dimethylbenzoyl) derivative of (R)-alaninol, (S)-leucinol, (1S,2R)-ephedrine and (S)-tert-leucinol and the O-(3,5-dinitrobenzoyl) derivative of (R)-phenylglycinol to silica gel through a carbamate or urea linkage. The CSPs were applied to the resolution of various racemic N-acyl-1-naphthylaminoalkanes by chiral HPLC, and the chromatographic resolution results were compared with those of previously reported CSPs (CSP 2, CSP 3), which are derived from N-(3,5-dinitrobenzoyl)-(1S,2R)-norephedrine and N-(3,5-dinitrobenzoyl-(R)-phenylglycinol. Based on a comparison of the resolution results for each CSP, the role of each functional group on the five chiral selectors is explained.

Use of Sulfated Cyclofructan 6 and Sulfated Cyclodextrins for the Chiral Separation of Four Basic Pharmaceuticals by Capillary Electrophoresis

Sulfated cyclofructan 6 (S-CF6) and sulfated cyclodextrins (S-α-, β-, γ-CDs) are highly selective chiral selectors for the enantioseparation of basic solutes. In this study, S-CF6 was introduced for the enantiomeric separation of four basic pharmaceuticals (including tamsulosin, tiropramide, bupivacaine, and norephedrine) by capillary electrophoresis (CE), and the enantiomeric separation performance was compared with S-α-, β-, γ-CDs. The effects of the chiral selector type, chiral selector concentration, operating voltage, and column temperature were examined and optimized. Excellent resolutions were obtained for all solutes on these chiral selectors.

FT-Raman Spectra of o-, m-, and p-Nitrophenol Included in Cyclodextrins

FT-Raman spectra of o-, m-, and p-nitrophenol included in α-cyclodextrin (CD), β-CD, hydroxypropyl (HP) β-CD, andsulfated β-CD were recorded. The phenyl ν(C=C) band of o- and p-nitrophenol in the CD inclusion complexes was shifted to higher wavenumber thanthat of pure o- and p-nitrophenol,whereas the phenyl ν(C=C) band of m-nitrophenol in the CD inclusion complexes was shifted to lower wavenumber than that of pure m-nitrophenol. The ring νCH peak of o-nitrophenol in the CD complexes was shifted to higher wavenumber than that of pure o-nitrophenol, whereas the ring νCH peak of m- and p-nitrophenol in the CD complexes was shifted to lower wavenumber than that of pure m- and p-nitrophenol.

Determination of optical purity of 3,5-dimethoxybenzoyl-leucine diethylamide by chiral chromatography and 1H and 13C NMR spectroscopy

(R)-N-3,5-dinitrobenzoyl (DNB) leucine derived chiral selector was used as an HPLC chiral stationary phase for the resolution of various racemic amino acids derivatives. In this study, determination of optical purity of an amino acid derivative was performed by chiral high performance liquid chromatography and 1H and 13C NMR spectroscopy by using the DNB leucine derived chiral selector. The accuracy and precision of each optical purity value are calculated and the data are compared to each other.

Comparison of monomeric and polymeric chiral stationary phases

Two-type polymeric chiral stationary phases (pCSPs) were prepared by surface grafting of chiral acryl-type monomers on a silica gel surface modified with 3-(trimethoxysilyl)propylmethacrylate. The prepared pCSPs were characterized by IR, Fr-Raman, scanning electron microscopy, and elemental analysis. In addition, two-type monomeric chiral stationary phases (mCSPs) were also prepared. The racemic analytes were separated using the prepared mCSPs and pCSPs. The separation factor (alpha) and capacity factor (k1) of the racemic analytes for the pCSP and mCSP were compared. The alpha and k1 values of the mCSP were higher than those of the pCSP.

Resolution of N-acyl-1-naphthylalkylamide on amide and sulfonamide-derived π-acidic chiral stationary phases

Two π-acidic chiral stationary phases (CSP 3, CSP 4) were prepared by connecting the N-3,5-dinitrobenzamide derivative or 2,4-dinitrobenzenesulfonamide derivative of (S)-leucinol to silica gel through the carbamate linkage. The CSPs were applied in resolving seven racemic N-acyl-1-naphthylaminoalkanes by chiral HPLC, and the chromatographic resolution results were compared. From the comparison of the resolution results of the two CSPs, the role of amide and sulfonamide group in each chiral selector of CSP 3 and CSP 4 and an iso-butyl and phenyl group on the chiral center of each CSP 2 and CSP 3 were explained.

Complexation of the Non-steroidal Anti-inflammatory Drug Loxoprofen with Modified and Unmodified β-Cyclodextrins

The inclusion complex of the anti-inflammatory drug, loxoprofen, with β-cyclodextrin-(CD), sulfated β-CD, and glycerol ether β-CD was studied by UV-VIS absorption and 1H-NMR spectroscopy in solution. The inclusion complex of loxoprofen with β-CDs was prepared by freeze-drying, and then characterized in the solid state by thermal analysis, X-ray diffraction, FT-IR and FT-Raman spectroscopy, and scanning electron microscopy (SEM). Furthermore, a physical mixture of loxoprofen/β-CD (1/1, mol-%) in the solid state was also characterized. The solubility of the loxoprofen increased on addition of β-CDs. The solubility enhancement of the loxoprofen with β-CDs is in the following order: glycerol ether β-CD > sulfated β-CD > β-CD.