• Journal of the Korean Chemical Society
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• v.53 no.2
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• pp.137-143
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• 2009

Liquid chromatographic enantiomer separation of N-tert-butoxycarbonyl (BOC) $\alpha$-amino acids and their ethyl esters was performed on covalently immobilized chiral column (Chiralpak IC) derived from polysaccharide derivative. The solvent versatility of the covalently immobilized Chiralpak IC in enantiomer separation of N-BOC $\alpha$-amino acid ethyl ester derivatives was shown and the chromatographic parameters of their enantioselectivities and resolution factors were greatly influenced by the nature of the mobile phase. Also the effect on the dissolving solvent for these analytes on the enantiomer separation using the same mobile phase and the examples of preparative enantiomer separation on analytical column were shown.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.49 no.2
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• pp.141-146
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• 2023

The efficient use of a chiral shift agent (3) containing bifunctional group (thiourea and tertiary amine) for the determination of the enantiomeric purity of racemic mixture (Hemiesters) has been studied. The diastereomeric complexes derived from a chiral shift agent (3) with various hemiesters gave rise to well separate signals of the methoxy protons of hemiesters. Good splitting signals for enantiomers of hemiesters in ¹H NMR are originated form the hydrogen bonds between carbonyl groups of hemiester and bifunctional groups of a chiral shift agent (3) such as thiourea moiety and tertiary amine. This study provides a quick and simple way to determine the chiral purity of hemiester using chiral transfer agent (3).

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.849-856
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• 1992

We prepared a simple, economic and versatile preparative system for an enantiomeric separation. Hydrophobic amino acid enantiomers were resolved in the preparative scale by a centrifugal liquid chromatography on the N-hexadecyl-L-proline coated reversed phase. The factors controlling the retention and resolution of racemic amino acids such as the concentration of Cu(Ⅱ), pH of the eluent, the type and content of organic modifier, and rpm of CLC were examined. Several mg of hydrophobic amino acid enantiomers were separated preparatively. To separate all of different amino acid enantiomers, various coating material will be investigated.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.76-84
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• 1990

Optical isomers of dansyl amino acids were separated by a chiral mobile phase addition method. Two metha and para isomers of xylenyl-L-proline were prepared and used as the ligands of copper(Ⅱ) chelate to resolve the dansyl amino acids. Their elution behaviors were similar to those obtained from the addition of copper (Ⅱ) benzyl-L-proline chelate. The matrix effect of the mobile phase such as pH, concentration of buffer and compositions of organic solvent acetonitrile affected the optical resolution. The separation mechanism could be explained by a cis-trans effect of the ligand exchange reaction and hydrophobic interaction between the ternary complex and the stationary phase.

• Analytical Science and Technology
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• v.22 no.2
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• pp.148-151
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• 2009

Enantiomer separation of N-fluorenylmethoxycarbonyl (FMOC) $\alpha$-amino acid was performed on covalently immobilized chiral column (Chiralpak IB) based on polysaccharide derivative as a chiral selector by reversed phase liquid chromatography. The effect of the reversed mobile phase on the chromatographic parameters of the enantioselectivities, resolution factors and retention times using covalently immobilized Chiralpak IB was shown. Also the enantiomer separation of N-FMOC $\alpha$-amino acid in the reversed and normal phase was compared and the results obtained in the former mobile phase were generally lower than those in the latter mobile phase.

• Journal of the Korean Chemical Society
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• v.30 no.2
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• pp.216-223
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• 1986

Separation of optical isomers of DNS derivatized amino acids by a reversed-phase high-performance liquid chromatography has been studied by adding a complex of an optically active amino acid (L-arginine) with the metal ion (Cu(II), Zn(II), Cd(II), Ni(II)) to the mobile phase. The separations are affected by the concentrations of acetonitrile, chelate and buffer. They are also affected by the pH and the kinds of metal and buffer. A separation mechanism, which is based on steric effect of the ligand exchange reaction for the formation of ternary complexes by the D,L-DNS-amino acids and the chiral additive associated with the stationary phase, is proposed to interpret the elution behaviors of D, L-dansyl-amino acids.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.44-50
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• 1990

The liquid chromatographic retention behavior of structural isomers of phenols was investigated by a change of the mobile phase properties. The retention behavior of structural isomer of phenols in reversed phase liquid chromatography was affected by eluent electrolyte added. It can be seen that this behavior is illustrated by a mechanism of Langmuir isotherm and ion exchange between phenolate and the reversed phase coated with ions. The retention behavior was represented as two different areas according to the concentration of the electrolytes. These areas can be explained as counter ion and co-ion effect, respectively. The maximum retention values were dependent not upon the kinds of organic modifier but upon the kinds of electrolyte.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.5
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• pp.427-436
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• 2010

A total of 18 surface sediments within the special conservation zone in the Masan Bay were analyzed to investigate the spatial distribution and polluted pathway of polybrominated diphenyl ehters(PBDEs). Twenty-two PBDE congeners were detected and brominated diphenyl ether-209 (BDE-209) among them was predominant. The concentrations of BDE-209 and ${\Sigma}_{21}$PBDEs (sum of 21 PBDE congeners without BDE-209) ranged from 2.32 to 64.2 ng/g and from 0.72 to 8.24 ng/g, respectively. The spatial distribution of both BDE-209 and ${\Sigma}_{21}$PBDEs showed a negative gradient from the inner to the outer Bay, indicating that the source of PBDEs might be mainly located inside the Bay such as streams and an effluent of wastewater treatment plants. It was seemed likely that the major parameters determining levels of PBDEs in the Masan Bay were the distance discharging from their sources as well as the characteristics and movement of sediments due to the flow of sea water.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.562-569
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• 1994

The retention data of twenty one monosubstituted phenols in the eluent systems containing 30∼70% of methanol or acetonitrile as organic modifiers, on $ C_{18}$ and Phenyl columns were collected to investigate the effect of the substituted groups on the retention of phenols. The capacity factors of the solutes except amino phenols are greater on $ C_{18}$ than on Phenyl column. And all the solutes have shown greater capacity factors in methanol-water than that in acetonitrile-water as a mobile phase. Generally the elution order between meta and para isomers of monosubstituted phenols in consistent (p < m) regardless of the polarity of the substituted group. But the elution order between ortho and meta isomers of phenol varies with regard to the polarity of the substituted group. The retention of the monosubstituted phenols has been influenced by the interaction between the solute and unreacted silanol of columns as well as the interaction between the solute and $ C_{18}$ or phenyl group of columns. And then, the effect of unreacted silanol on the retention of the monosubstituted phenols is greater on $ C_{18}$ than on Phenyl column. And the greater hydrogen bonding acceptor basicity(${\beta}$) of the substituted group is, the greater this effect is. The relationship between the retention of the monosubstituted phenols and their parameters such as van der Waals volume(VWV) and hydrogen bonding acceptor basicity(${\beta}$) has been investigated. The good linearity has been observed in the plot log k' vs. (1.01VWV/100-1.84${\beta}$). In consequence, the retention of the monosubstituted phenols on $ C_{18}$ and Phenyl columns can be easily predicted by the parameter (1.01VWV/100-1.84${\beta}$).

• Journal of the Korean Magnetics Society
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• v.1 no.1
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• pp.1-5
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• 1991

The magnetic properties of the polycrystalline ${(Fe_{2}O_{3})}_{1-x-y}{(In_{2}O_{3})}_{x}{(Eu_{2}O_{3})}_{y}$(x=0.01, y=0.02과 x=0.02, y=0.03) have been studied by the methods of X-ray diffraction, $M\"{o}ssbauer$ effect, and magnetic hysteresis measurement. The X-ray diffraction patterns show that the samples have a same crystal structure as $\alpha-Fe_{2}O_{3}$. From the analysis of the temperature dependence of the quadrupole splitting and average half-width, it is found that the Morin transition occurs in the sample of x=0.01 and y=0.02 and the spin angle defined as the angle between the [111] crystal axis and antiferromagnetic vector, changes from about $35^{\circ}$ to the (111) plane as increasing the temperature in the sample of x=0.02 and y=O.03. The temperature dependence of magnetic hyperfine field is analyzed by using the spin-wave theory. The isomer shift values at room temperature are found to be given by about 0.35mm/s for the samples which means that the Fe ions belong to $3^{+}ion$. The temperature dependence of isomer shift was analyzed by using the Debye model.