• Bulletin of the Korean Chemical Society
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• v.16 no.10
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• pp.977-980
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• 1995

A new chiral stationary phase (CSP 2) derived from cyclohexylamide of (S)-naproxen has been prepared. CSP 2 has shown greater enantioselectivities for the two enantiomers of N-(3,5-dinitrobenzoyl)-a-amino esters and amides than the CSP derived from 3,5-dimethylanilide of (S)-naproxen (CSP 1) as expected from the reciprocity conception of chiral recognition. However, CSP 2 has been found to be worse than CSP 1 in resolving N-(3,5-dinitrobenzoyl)-a-arylalkylamines, supporting the previously proposed chiral recognition mechanism which utilizes the 3,5-dimethylphenyl group of CSP 1 as an alternative π-basic interaction site. In addition, CSP 2 has been found to be reasonably good in resolving the two enantiomers of a variety of other π-acidic racemates.

• Bulletin of the Korean Chemical Society
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• v.15 no.6
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• pp.497-502
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• 1994

A new chiral stationary phase (CSP) for the liquid chromatographic resolution of enantiomers was prepared from (S)-naproxen and 3,5-dinitroaniline. The 6-alkoxy-2-naphthyl group of the CSP was presumed to act as a ${\pi}$-basic interaction site for resolving ${\pi}$-acidic racemates while the 3,5-dinitroanilide group of the CSP was presumed to play a role as a ${\pi}$-acidic interaction site for resolving ${\pi}$-basic racemates. From the chromatographic resolution trends of N-alkylamide derivatives of ${\alpha}$-arylalkylamines on the CSP prepared, the chiral recognition mode involving the intercalation of the amide alkyl chain of the less retained enantiomers between the connecting tethers of the CSP was proposed.

• Analytical Science and Technology
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• v.34 no.4
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• pp.180-190
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• 2021

This study compared the efficacy of chiral GC and chiral HPLC for the analysis of nicotine. To develop a suitable dispersive liquid-liquid microextraction (DLLME) method, the following parameters were optimized: pH, extraction solvent, dispersive solvent, type and quantity of salt, and laboratory temperature. The validation of the method was carried out by the established HPLC method. The LODs were 0.11 ㎍/mL and 0.17 ㎍/mL for the (S)- and (R)- enantiomers, respectively. The LOQs were 0.30 ㎍/mL and 0.44 ㎍/mL, respectively. The optimal calibration range was between 0.30-18 ㎍/mL and 0.44-4.40 ㎍/mL, respectively, and the correlation coefficient (r²) was 0.9978-0.9996. The intra-day accuracy was 79.9-110.6 %, and the intra-day precision was 1.3-12.0 %. The inter-day accuracy was 87.8-108.0 %, and the inter-day precision was 4.0-12.8 %. E-liquid and biological fluids (urine and saliva) were analyzed using the established method.

• YAKHAK HOEJI
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• v.53 no.2
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• pp.60-68
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• 2009

In terms of chiral issue, two enantiomers of chiral drugs often differ significantly in their pharmacological, toxicological and pharmacokinetic profile. Chiral switches of racemic drugs have been redeveloped as single enantiomers. Several chiral resolution techniques in chirotechnology are introduced and the most used chiral HPLC chromatographic method among several chiral analysis techniques is described with its several advantages. Several types of chiral HPLC columns derived from their chiral selectors are discussed with their property and applications for enantiomer separation.

• Bulletin of the Korean Chemical Society
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• v.8 no.1
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• pp.45-47
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• 1987

After conversion to their 3,5-dinitrobenzoyl or 3,5-dinitroanilide derivatives, the enantiomers of a number of drugs may be chromatographically separated on various ${\alpha}$-arylalkylamine-derived chiral stationary phases (CSPs). While each CSP used in this study is useful, CSP 1 is best able to resolve the 3,5-dinitroanilide derivative of Ibuprofen while CSP 9 generally gives rather large ${\alpha}$ values for the resolution of 3,5-dinitrobenzoyl derivatives of the enantiomers of ${\beta}$-adrenergic blocking drugs.

• Preventive Nutrition and Food Science
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• v.13 no.1
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• pp.54-59
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• 2008

This study was conducted to investigate the effect of pH on the formation of furfural compounds from glucose and fructose reacting with amino acid enantiomers in the Maillard reaction. Hydroxymethylfurfural (HMF) content was highest at pH 4.0, and decreased with increasing pH. HMF was significantly higher in glucose-based systems than fructose-based systems. Furfuryl alcohol (FFA) and 5-methyl-2-furaldehyde (MF) were not increased with increasing pH, and only small amounts were formed. In addition, 2-furaldehyde (F) was found to increase in the systems, as pH increased. However, the content was small and variable. 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) was only found in Glc/D-Asn, Glc/L-Lys and Fru/D-Lys system, but the content was not increased with increasing pH. 2-acetylfuran (AF) was higher in Glc (or Fru)/L-Lys and Glc (or Fru)/D-Lys systems at pH 7.0. However, at pH 4.0, the content of AF was higher in the Glc (or Fru)/Gly and Glc (or Fru)/L-Asn systems. Therefore, this study aimed to observe the effect of pH, sugars and amino acid enantiomers on the production of furfural and related compounds by the Maillard reaction. A clear tendency was observed for some classes of compounds to be more easily formed at higher or lower pH. HMF was more readily formed at lower pH, while FFA, F, DMHF and MF were inhibited by acidic conditions. Particularly, compounds like FFA, F and MF were not affected by pH changes. In addition, DMHF and MF were only formed in L-Lys and D-Lys system.

• Analytical Science and Technology
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• v.33 no.2
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• pp.59-67
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• 2020

Nadolol is a β-blocker drug, which effectively manages hypertension and angina pectoris. Its chemical structure allows the formation of four possible stereoisomers. A coupled column high-performance liquid chromatographic (HPLC) system with UV and fluorescence detection was investigated for simultaneously determining four nadolol enantiomers in human plasma. The plasma samples were prepared using a convenient liquid-liquid extraction process and passed through HPLC. Nadolol was initially separated from the endogenous compounds or other impurities in human plasma on a Phenomenex silica column, and its enantiomers were resolved and determined on a Chirapak AD-H column. The developed HPLC method achieved an effective chiral separation and significantly eliminated endogenous compound interference. This optimal HPLC method was validated following FDA guidelines. The results showed good selectivity, linearity, accuracy (90.50 % - 105.27 %), and precision (RSDs < 9.52 %) for each enantiomer. This method was also successfully applied to determine nadolol enantiomers in the plasma samples of a healthy male volunteer (after orally administering 80 mg racemic nadolol), proving its suitability for nadolol stereoselective pharmacokinetic studies.

• Archives of Pharmacal Research
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• v.23 no.2
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• pp.178-181
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• 2000

In order to study the simultaneous determination of (+)- and (-)-cetirizine in human urine we have developed a chiral separation method by HPLC. A chiral stationary phase of $\alpha$$_1$-acidglycoprotein, the AGP-CSP was used to separate the enantiomers. The pH of the phosphate buffer, as well as the content of the organic modifier in the mobile phase, markedly affected the chromatographic separation of (+)- and (-)-cetirizine. A mobile phase of 10 m㏖/1 phosphate buffer (pH 7.0)-acetonitrile (95 : 5, v/v) was used for the urine assays. Ultraviolet absorption was monitored at 230nm and roxatidine was employed as the internal standard for quantification. (+)-Cetirizine, (-)-cetirizine and the internal standard were eluted at retention times of 12, 16, and 32 mins, respectively. The detection limit for cetirizine enantiomers was 400 ng/$m\ell$ of urine. A pharmacokinetic study was conducted with the help of 5 healthy female volunteers who were administered with a single oral dose of racemic cetirizine (20 mg). The peak area ratios provided by the cetirizine enantiomers were linear(r>0.997) over a concentration range of 2.5-200 ${\mu}g/ml$. The peak of the excreted cetirizine enantiomers appeared in the urine sample during the period of 1-2 hrs following the administration of the oral dose. The excreted level of (+)-cetirizine was slightly higher than (-)-cetirizine but the difference was not statistically significant. However, this method appears to have applications for enantioselective pharmacokinetic studies of racemic drugs.

• Archives of Pharmacal Research
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• v.26 no.2
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• pp.114-119
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• 2003

A high performance liquid chromatographic (HPLC) method was developed for the qualitative and quantitative determination of benzophenanthridine alkaloids from the methanol extracts of Hylomecon hylomeconoides and H. vernale (Papaveraceae). Achiral and chiral methods were adapted for the separation of 6-methoxydihydrosanguinarine (1), 6-acetonyldihydrosanguinarine (2) and dihydrosanguinarine (3). The achiral reversed phase HPLC method made it possible the simultaneous separation and determination of 1, 2 and 3 within 20 min on ODS column using acetonitrile-phosphate buffer (50 mM, pH 7.0) (50 : 50, v/v). The separation and determination of 1 and 2 enantiomers was available using chiral columns. The same amount of (+) and (-)-enantiomers of 1 was found from the methanol extract of specimen, indicated that 1 could be the artifact produced by the reaction of sanguinarine with methanol. H. hylomeconoides showed higher level of 1 and 3 in compared with H. vernale, especially in root samples permitting the possibility of chemical discrimination between two species.

• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.411-415
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• 1990

The dabsylation of amino acids has been applied to resolve their optical isomers with the use of chiral mobile phase in high performance liquid chromatography. The dabsyl amino acids were successfully separated on reversed phase column($C_{18}$) by adding a chiral L-benzylproline-Cu(II) chelate to the mobile phase. The separation selectivity of the dabsyl amino acid enantiomers was not less than that of dansyl amino acids. The retention order of the dabsyl amino acid enantiomers was as those of the dansyl amino acid enantiomers except dabsyl threonine. The optical selectivity of the dabsyl amino acids increase with pH of the mobile phase and concentration of the chelate, but slightly decreases with concentration of buffer and organic solvent composition. However serine, methionine, valine, and leucine showed a slight decrease in the optical selectivity with increase in pH. The retention times of the dabsyl amino acids decreases with increasing pH and acetonitrile concentration but increases with the concentration of the chiral chelate added. The mechanism of the optical resolution is based on a stereospecific interaction including a intramolecular hydrophobic effect and SN-2 reactivity of the ligand exchange chromatography.It is advantageous to detect absorption at 436 nm, which is less interferent them the other detection systems. The derivatized dabsyl amino acids are stable for a month.