• Journal of the Korean Applied Science and Technology
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• v.10 no.1
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• pp.9-22
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• 1993

Recent studies on enzyme reactions in organic solvents are revived. The reactions are classified into three categories: heterogeneous, biphasic and homogeneous systems. The following subjects are described and discussed about the heterogeneous system. 1) The maximal expression of enzyme activity in organic solvents in terms of water content, hydration of enzyme, and equilibriun of water between enzyme and substrate solution. 2) Solvent effect on the catalytic power of enzyme. 3) Thermostability and thermoreactivity. 4) Applications of the enzyme reactions to synthetic chemistry.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3267-3273
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• 2011

Ag(I) carboxylate gelators with mixed-ligands were systemically investigated to understand the mechanism of the organic gel formation. The gelators constructed 3-D networks of nanometer-sized thin fibers which facilitated gel formation in various aromatic organic solvents, even at very low concentrations. The loss of reflection peaks in the X-ray diffraction data indicated the reduction of strong interactions between the long alkyl chains as the Ag(I) carboxylates formed gels by maximizing their interactions with the organic solvents. The gelation temperature ($T_{gel}$) was measured to explore the interaction between the gelator molecules and solvents depending on their composition and concentration. Based on the gelation phenomena, a dissociation/re-association mechanism was proposed.

• Environmental Mutagens and Carcinogens
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• v.19 no.2
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• pp.102-107
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• 1999

A population monitoring studies for assessing the genotoxicity of occupationally exposed mixed organic solvents to printers were performed by using the chromosome aberration assay and the cytokinesis-blocked micronucleus assay. The incidence of chromosome aberrations and micronuclei was studied in the peripheral blood lymphocytes of 51 male printers and their matched controls in Seoul area. Smoking habits and duration of employment were taken into account. The frequencies of micronucleus in peripheral lymphocytes of printers were significantly different in comparision with control subjects. Also there were significant increase in the frequencies of micronucleus by duration of exposure. The frequencies of chromosome aberrations showed no significant differences between printers and their matched controls.

• Journal of Photoscience
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• v.12 no.3
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• pp.119-122
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• 2005

The photophysical properties of coumarin 6 laser dye have been studied in two solvents; ethanol and acetonitrile using steady-state fluorescence depolarization technique. The experimentally measured reorientation time of coumarin 6 is more or less the same in given solvents at particular temperature. It is found that coumarin 6 rotates slower in acetonitrile than in ethanol especially at higher values of viscosity over temperature. We also measure the ground and excited state dipole moments of coumarin 6 by solvent perturbation method. The results found that excited state dipole moment is greater than ground state dipole moment, which indicates that excited state is more polar than the ground state.

• Journal of the Korean Chemical Society
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• v.22 no.1
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• pp.7-11
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• 1978

The reactions of 2,4-dinitroiodobenzene with para subtituted anilines in acetonitrile-methanol binary solvent mixtures have been studied. Rate constants for reactions in methanol rich solvents are greater than for reactions in acetonitrile rich solvents. Kinetic results show that the bond formation step is rate determining in the solvent system studied. The solvent effect can be explained by stabilization of the transition state by formation of hydrogen bond between oxygen atom of methanol and hydrogen atom of aniline.

• Journal of Microbiology and Biotechnology
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• v.12 no.5
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• pp.793-800
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• 2002

The mycolic acids and fatty acids of mycolic acid- containing bacteria in various types of fluids were analyzed using capillary gas chromatography and mass spectrometry. As model strains, Brevibacterium and Coryebacterium species, which have corynomycolic acids ill the range of $C_{32}C_{36}$ in the whole cell, were investigated. Optimized solvents extraction procedures for the mycolic acids and fatty acids from the culture fluids were: chloroform/methanol (1:2, v/v) as the first extraction solvents fur 4 h; and chlorofunuwater (1:1, v/v) as the second extraction solvents far 1 h. These conditions gave above 95% recovery yields fur mycolic acids from the culture fluids. The mycolic acid profile for the whole cells and the culture fluids were similar fur all the media tested. Thus, the procedure described here could be applied for the identification of mycolic acid-containing bacteria in fermentation broth or liquid from of foods.

• Journal of environmental and Sanitary engineering
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• v.16 no.1
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• pp.66-71
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• 2001

The objective of this study was to depict the kinetic behavior of the platinum catalyst for the deep oxidation of aromatic solvents and their binary mixtures. The oxidation kinetics of aromatic solvents, which were benzene, toluene and m-xylene, was studied on a 0.5% $Pt/{\gamma}-Al_2O_3$ catalyst. Deep oxidation of binary mixtures, which were 1:1 in volume, was carried out and the inlet concentration was controlled in the range of 133 and 333ppmv. An approach based on the two-stage redox model was used to analysis the results. The deep oxidation conversion of aromatic solvents was inversely proportional to inlet concentration in plug flow reactor. This trend is due to the zeroth-order kinetics with respect to inlet concentration. The kinetic parameters of multicomponent model were independently evaluated from the single compound oxidation experiments. A simple multicomponent model based on two-stage redox rate model made reasonably good predictions of conversion over the range of parameters studied.

• Journal of Photoscience
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• v.4 no.3
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• pp.105-112
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• 1997

The fluorescence quenching of 2, 5-di-(5-tert-butyl-2-benzoxazolyl)-thiophene (BBOT) by aniline in five different solvents namely heptane, hexane, cyclohexane, dioxane and acetonitrile has been carried out at room temperature with a view to understand the quenching mechanisms. The experimental results show positive deviation in the Stern-Volmer plots in all the solvents. In order to interpret these results we have invoked the Ground state complex and sphere of action static quenching models. Using these models various rate parameters have been determined. The magnitudes of these parameters suggest that sphere of action static quenching model agrees well with the experimental results. Hence this positive deviation is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check these bimolecular reactions as diffusion-limited and to estimate independently distance parameter R$^1$ and mutual diffusion coefficient D. Finally an attempt has been made to correlate the values of R$^1$ and D with the values of the encounter distance R and the mutual diffusion coefficient D determined using the Edward's empirical relation and Stokes-Einstein relation.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.595-606
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• 2000

In order to compare analytical conditions for measuring PAHs(polycyclic aromatic hydrocarbons) in ambient air, a series of experiment were conducted using three different types of extraction methods that include:(1) accelerated solvent extraction (ASE), (2) soxhlet, and (3) sonification methods. Efficiency and relevant analytixal parameters for each of these methods were examined on five different types of solvents that include:(1) 10% diethyl ether in n-hexane(v/v), (2) dichloromethane, (3)cyclohexane.(4) toluene, and (5) Benzene: ethanol (4:1). Comparison of extraction efficiency for various combinations between methods and solvents was made through an application of both internal and external standard calibration techniques. The extraction efficiency tests, when checked using both internal and external standards, allowed us to derive meaningful comparison among different techniques and among solvents.

• Textile Coloration and Finishing
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• v.16 no.2
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• pp.8-14
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• 2004

The purpose of this study was to investigate dyeing properties and antibacterial activities of cotton and silk fabrics treated with Ginkgo biloba leaf extracted with three kinds of aqueous solvents: distilled water, electrolytic reduction water and electrolytic oxidation water. The optimum dyeing condition of Ginkgo biloba leaf was 120 min at 8$0^{\circ}C$. Electrolytic reduction water had the highest dyeability to both cotton and silk compared with electrolytic oxidation water and distilled water. A color of extract by distilled water and electrolytic oxidation water showed yellowish Yellow Red, extract by electrolytic reduction water showed reddish Yellow Red. Irrespective of kinds of extraction solvents, appropriate acidity of medium was pH 9∼11 and pH 3 for cotton and silk fabrics, respectively. Colorfastness to laundering and Light fastness showed generally low but crocking fastness was excellent. Antibacterial activities of the treated fabrics above were 99.9%.