• Bulletin of the Korean Chemical Society
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• v.15 no.1
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• pp.74-77
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• 1994

Rare earth elements (REE) were individual separated by applying the gradient elution via HPLC using ${\alpha}-hydroxyisobutyric$ acid (HIBA) as an eluent. However, the overlap of Y and Dy peaks was too severe to obtain the resolution of these two peaks. The target transformation factor analysis (TTFA) was applied to resolve the elution peaks of Y and Dy. [A]$_{raw}$ formed from the absorbances of mixed solution was factor analyzed. The abstract factor analysis(AFA) was used to determine the number of components that contributed to the poorly resolved peaks. The error theory in the AFA showed that the number of components was 2. The test vectors which correspond to pure component were selected from the standard solutions of Y and Dy. TTFA was accomplished by target testing. The results showed that the resolution of two peaks as well as the determination of Y and Dy were possible by the factor analysis.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.617-618
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• 1998

A simple and reproducible pretreatment method was developed for the determination of dioxins in milk sample. Liquid-liquid extraction (LLE) was used for the initial extraction of the analyte from milk. For the elimination of interferences coextracted from milk, acid treatment followed by multilayer silica gel, and then alumina column clean-up were performed. The clean extract could be obtained without carbon column or high performance liquid chromatographic (HPLC) clean-up procedure. Polychlorinated biphenyles (PCBs) and dioxins were separated on neutral alumina activated at 180 ℃ for 12 hours. The final extract was analyzed by HPLC and high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). The recovery of dioxins spiked in milk at 75-300 ppt level was 83.3-98.9% and their relative standard deviation was 4.1-14%.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.619-624
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• 1998

A simple and reproducible pretreatment method was developed for the determination of dioxins in milk sample. Liquid-liquid extraction (LLE) was used for the initial extraction of the analyte from milk. For the elimination of interferences coextracted from milk, acid treatment followed by multilayer silica gel, and then alumina column clean-up were performed. The clean extract could be obtained without carbon column or high performance liquid chromatographic (HPLC) clean-up procedure. Polychlorinated biphenyles (PCBS) and dioxins were separated on neutral alumina activated at 180 ℃ for 12 hours. The final extract was analyzed by HPLC and high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). The recovery of dioxins spiked in milk at 75-300 ppt level was 83.3-98.9% and their relative standard deviation was 4.1-14%.

• KSBB Journal
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• v.11 no.5
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• pp.529-535
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• 1996

Methyl frucloside was purified from the aqueous sugar/methyl fructoside solution by liquid chromatography using Amberlite IRA-900, strong anion-exchange resin. The optimum operating conditions, resolution and productivity of methyl fructoside were discussed to evaluate the practical feasibility of the proposed chromatographic separation process of methyl fructoside which is useful as a new starting material for sugar ester synthesis. The linear chromatography model with HETP was well applied to the chromatographic separation process of methyl fructoside and the theoretical solution successfully predicted the elution chromatogram of methyl fructoside and sucrose at different superficial linear velocity of eluent for rectangular feed with different loading volume of packed bed. The optimum operating conditions were found to be 75% with the loading volume of packed bed at 1.13 cm/min of the superficial linear velocity at $60^{\circ}C$, and gave the productivity of methyl fructoside of 7 mg/g-resin/h with the resolution of 1.1.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.2978-2982
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• 2013

A doubly tethered $N-CH_3$ amide chiral stationary phase (CSP 4) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was applied to the resolution of an antiarrythmic agent, tocainide, and its analogues and the chromatographic resolution results were compared with those on a singly tethered N-H amide CSP (CSP 1), a singly tethered $N-CH_3$ amide CSP (CSP 2) and a doubly tethered N-H amide CSP (CSP 3) under an identical aqueous mobile phase condition. CSP 4 was found to be generally better than other CSPs in terms of the separation factors (${\alpha}$) and resolutions (RS). The retention times of analytes denoted by the retention factors ($k_1$) on CSP 4 were quite long compared to those on other CSPs because of the improved lipophilicity of CSP 4. The long retention times of analytes on CSP 4 were successfully controlled by the addition of a small amount of ammonium acetate to aqueous mobile phase without hurting the chiral recognition efficiency. The variation of the content and type of organic and acidic modifier in aqueous mobile phase was found not to change the chiral recognition efficiency significantly.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1551-1554
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• 2010

Two diastereomeric chiral stationary phases (CSPs) were applied to the liquid chromatographic resolution of various racemic ${\alpha}$-amino methyl esters, ${\alpha}$-amino N,N-diethylamides and ${\alpha}$-amino N-propylamides. The CSP incorporating (R)-3,3'-diphenyl-1,1'-binaphtyl and (R,R)-tartaric acid unit as chiral barriers did not show any chiral recognition. In contrast, the CSP incorporating (R)-3,3'-diphenyl-1,1'-binaphtyl and (S,S)-tartaric acid unit as chiral barriers was found to show excellent chiral recognition especially for the two enantiomers of ${\alpha}$-amino N-propylamides. Some of ${\alpha}$-amino methyl esters and ${\alpha}$-amino N,N-diethylamides were also resolved on the CSP incorporating (R)-3,3'-diphenyl-1,1'-binaphtyl and (S,S)-tartaric acid unit. From these results it was concluded that the two chiral units composing the diastereomeric CSPs can show "matched" or "mismatched" effect on the chiral recognition according to their absolute stereochemistry.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1775-1779
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• 2006

A liquid chromatographic chiral stationary phase (CSP) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxilic acid without extra free aminopropyl groups on silica surface has been demonstrated to be quite effective for the resolution of various $\beta$-amino acids. The retention factors ($k_1$) for the resolution of $\beta$-amino acids on the CSP were quite large and the large retention factors might be quite attractive along with the reasonable separation factors ($\alpha$) for preparative scale enantioselective chromatography. The large retention factors on the CSP were found to be reduced effectively by adding ammonium ion to mobile phase without sacrificing the chiral recognition efficiency of the CSP. Consequently, the CSP is also quite applicable for use in analytical enantioselective chromatography.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1105-1109
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• 1998

A chiral stationary phase derived from (S)-N-(3,5-dinitrobenzoyl)leucine N-phenyl N-alkyl amide (CSP 2) was applied in separating the two enantiomers of various π-basic aromatic derivatives of leucine N-propyl amide in order to evaluate π-basic aromatic groups as an effective derivatizing group for the resolution of a-amino acids. Subsequently N-(3,5-dimethoxybenzoyl) group was found to be very effective as a π-basic aromatic derivatizing group. Based on these results, N-(3,5-dimethoxybenzoyl) derivatives of various a-amino N-propyl amides, N,N-diethyl amides and esters were resolved on the CSP derived from (S)-N-(3,5-dinitrobenzoyl) leucine N-phenyl N-alkyl amide (CSP 2) and the resolution results were compared with those on the CSP derived from (S)-N-(3,5-dinitrobenzoyl)leucine N-alkyl amide (CSP 1). The enantioselectivities exerted by CSP 2 were much greater than those exerted by CSP 1. In addition, racemic N-(3,5-dimethoxybenzoyl)-a-mino N,Ndiethyl amides were resolved much better than the corresponding N-(3,5-dimethoxybenzoyl)-a-mino N-propyl amides and esters on both CSPs. Based on these results, a chiral recognition mechanism utilizing the π-π donor-acceptor interaction and the two hydrogen bondings between the CSP and the analyte was proposed.

• Analytical Science and Technology
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• v.36 no.4
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• pp.143-151
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• 2023

Considering the greater role of α-amino acids in our daily lives, the enantiomer resolution of seven α-amino acids derivatized with fluorogenic reagent (4-fluoro-7-nitro-2,1,3-benzoxadiazole, NBD-F) by chiral HPLC on amylose or cellulose trisphenylcarbamate derived chiral stationary phases (CSPs) under simultaneous ultraviolet (UV) and fluorescence (FL) detection was performed. The degree of enantioseparation and resolution was affected by nature and selector backbones of the CSPs as well as the kind of amino acids. Baseline enantiomer separation and resolutions were observed for the enantiomers of all analytes as NBD derivatives especially on coated type amylose tris(3,5-dimethylphenylcarbamate) derived CSPs (Chiralpak AD-H and Lux Amylose-1). The other CSPs also showed good enantioselectivity except for the CSPs (Chiralpak IB, Chiralcel OD-H and Lux Cellulose-1) having cellulose tris(3,5-dimethylphenylcarbamate) as chiral selectors. The developed analytical chiral method was applied to determine the enantiomeric purity of seven commercially available L-α-amino acids and the impurities as D-forms were found to be in the range 0.08-0.87 %, respectively. The intra- and interday accuracy and precision assays showed high accuracy and precision of the developed analytical method. This chiral HPLC method for the enantiomer resolution of amino acids using fluorescent derivatization could be useful for the determination of enantiomeric purity of pharmaceuticals and biological study for amino acid type compounds among chiral drugs.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.3017-3021
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• 2011

Two chiral stationary phases (CSPs) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 bonded covalently to silica gel were applied for the first time to the resolution of racemic vigabatrin and its analogue ${\gamma}$-amino acids and the resolution results were compared to those on the commercially available Crownpak CR(+) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 coated dynamically onto octadecylsilica gel. While vigabatrin was not resolved at all on Crownpak CR(+), it was resolved quite well on the two CSPs. Among four vigabatrin analogue ${\gamma}$-amino acids, only two were resolved on Crownpak CR(+), but three were resolved on the CSP (CSP 1) containing residual silanol groups and all of four were resolved on the CSP (CSP 2) containing residual silanol group-protecting n-octyl groups. The improved lipophilicity in CSP 2 was proposed to be responsible for its superiority to CSP 1 for the resolution of vigabatrin and analogue ${\gamma}$-amino acids. In addition, the composition of aqueous mobile phase was found to affect the chiral recognition behaviors for the resolution of vigabatrin and analogue ${\gamma}$-amino acids on CSP 2.