• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.562-567
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• 2007

The stereoselective synthesis of chiral terminal epoxide is of immense academic and industrial interest due to their use as versatile starting materials as well as chiral intermediates. In this study, new polymeric chiral Co(salen) complexes bearing tallium (III)chloride and iron (III)chloride (ferric chloride) have been synthesized and characterized. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides using water and phenol derivatives as nucleophiles. The easily prepared polymeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ and phenol nucleophiles, providing enantiomerically enriched terminal epoxides (> 98% ee). The system described in this work is very efficient for the synthesis of chiral epoxide, 1,2-diol and ${\alpha}$-aryloxy alcohol intermediates.

• Journal of the Korean Chemical Society
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• v.52 no.1
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• pp.16-22
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• 2008

on-line system for preconcentration and separation of lead(II) is presented. The method is based on the complex formation of Pb(II) with adsorbed Methyl thymol blue on activated carbon. The conditions of preparing the solid phase reagent and of quantitative recovery of Pb(II) from diluted solutions, such as acidity of aqueous phase, solid phase capacity, and flow variables were studied as well as effect of potential interfering ions. After preconcentration step, the metal ions are eluted automatically by 5 ml of 0.5 M HNO3 solution and the lead ions content was determined by flame atomic absorption spectrometry. Under the optimum conditions, the lead ions in aqueous samples were separated and preconcentrated about 1000-fold by the column. The detection limit was 0.001 g mL-1. Lead has been determined in river and tap water samples, with recovery of 98 to 102%.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1532-1534
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• 2003

We attempted to fabricate a dendrimer Langmuir-Blodgett(LB) films containing 48 pyridinepropanol functional end group. As the pyridinepropanol functional group could form a complex structure with metal ions. In this study the samples for electrical measurement were fabricated to two types metal complexes with $Pt^{4+}$ ions by LB method. And we have investigated the surface activity at the air-water interface as well as the electrical properties for the monolayers of G4-48PyP dendrimer complex with metal ions($Pt^{4+}$ ions) by different method. In the surface pressure-area(${\pi}$-A) isotherms of the dendrimers, the stable condensed films formed at the air-water interface and the different method of metal complex showed the difference on molecular behavior. We have studied the electrical properties of the ultra thin dendrimer LB films investigated by the current-voltage (I-V) characteristics of metal/dendrimer LB films/metal(MIM) structure. In conclusion, it is demonstrated that the metal ion around G4-48PyP dendrimer can contribute to make formation of network structure among dendrimers and it result from the change of electrical properties.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.16-18
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• 2002

We attempted to fabricate a dendrimer Langmuir-Blodgett(LB) films containing 48 pyridinepropanol functional end group. As the pyridinepropanol functional group could form a complex structure with metal ions. In this study the samples for electrical measurement were fabricated to two types metal complexes with $Pt^{4+}$ and $Fe^{2+}$ ions by LB method. And we have investigated the surface activity at the air-water interface as well as the electrical properties for the monolayers of pure G4-48PyP dendrimer and its complex with metal ions($Pt^{4+}$ and $Fe^{2+}$ ions). In the surface pressure-area($\pi-A$) isotherms of the dendrimers, the stable condensed films formed at the air-water interface and the metal ions effect showed the difference on molecular behavior. We have studied the electrical properties of the ultra thin dendrimer LB films investigated by the current-voltage(I-V) characteristics of metal/dendrimer LB films/metal(MIM) structure. In conclusion, it is demonstrated that the metal ion around G4-48PyP dendrimer can contribute to make formation of network structure among dendrimers and it result from the change of electrical properties.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.5
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• pp.589-594
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• 2007

The effect of synergists having chelating ability on inhibiting browning were studied with a giucose-glutamic acid model for doenjang containing citric acid as the anti-browning agent and iron ion. The model solutions were prepared by dissolving 0.1 M glucose, 0.1 M glutamic acid, 50 mM citric acid, 0.2 mM $FeCl_2$ and synergist in 1 M phosphate buffer (pH 7.0), heating at $50^{\circ}C$ for 24 hr and storing at $30^{\circ}C\;or\;40^{\circ}C$ for four weeks. Synergists were chitosan, gallic acid, methyl benzoate, pyrophosphate and tannic acid; they were used at the following concentrations: gallic acid, pyrophosphate and tannic acid at 0.015% and 0.15%; chitosan and methyl benzoate at 0.0075% and 0.015%. Anti-browning capacities had a tendency to decrease greatly after three weeks in the case of storage at $30^{\circ}C$, whereas they decreased with storage time during storage at $40^{\circ}C$. However, anti-browning capacities of samples containing 0.015% tannic acid and 0.15% pyrophosphate were higher than that of sample without synergist by 32% after storage at $30^{\circ}C$ for four weeks. Gallic acid, tannic acid and pyrophsphate also inhibited the formation of Maillard reaction intermediates such as fluorescent compound and 3-deoxyglucosone due to the high chelating ability with iron ion after four weeks of storage at $30^{\circ}C$. The effect of these compounds on the inhibition of formation of Maillard reaction intermediates was higher at 0.15% than at 0.015%. Moreover, gallic acid increased the browning by forming colored complexes, and tannic acid generated black precipitates. Therefore, pyrophosphate of food additives was found to be the most useful synergist of citric acid, the anti-browning agent for doenjang.