• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.485-495
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• 1992

The viscosities of organic compounds (alcohols, acetates, alkanes, acids, substituted $NH_2$) in liquid states, gas states and the binary mixtures of n-alkane / 1-chloroalkane were calculated by molecular modeling techniques. The molecular descriptors of molecular modeling technique are Molecular connectivity indices, Wiener indices and ad hoc descriptors, which can encode the information of compound properties about the effect of size, branching, cyclization, unsaturation, heteroatom content, polarizability, and so on. The successful results among method have been Molecular connectivity indices, binary mixtures of n-alkane / 1-chloroalkane, Wiener indices for gas state and ad hoc descriptor for liquid states. Also we obtained the regression equations for viscosities using molecular modeling indices for gas, liquid states and binary mixtures of n-alkane / 1-chloroalkane. The calculated viscosity values for organic compounds are in good agreement with experimental results.

• Journal of the Korean Physical Society
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• v.73 no.10
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• pp.1437-1443
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• 2018

In this work, $SnO_2$ modified with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) separately and combined sensitized by using the co-precipitation method and their sensing behavior toward ethanol vapor at room temperature were investigated. An interdigitated electrode (IDE) gold substrate is very expensive compared to a fluorine doped tin oxide (FTO) substrate; hence, we used the latter to reduce the fabrication cost. The structure and the morphology of the studied materials were characterized by using differential thermal analyses (DTA) and thermogravimetric analysis (TGA), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller surface area and Barrett-Joyner-Halenda (BJH) pore size measurements. The studied composites were subjected to ethanol in its gas phase at concentrations from 10 to 200 ppm. The present composites showed high-performance sensitivity for many reasons: the incorporation of $SnO_2$ and CNTs which prevents the agglomeration of rGO sheets, the formation of a 3D mesopourus structure and an increase in the surface area. The decoration with rGO and CNTs led to more active sites, such as vacancies, which increased the adsorption of ethanol gas. In addition, the mesopore structure and the nano size of the $SnO_2$ particles allowed an efficient diffusion of gases to the active sites. Based on these results, the present composites should be considered as efficient and low-cost sensors for alcohol.

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.269-272
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• 2015

$La_2Ce_2O_7$ and $CeO_2$ membranes were fabricated from the corresponding powders derived from sol-gel process with polyvinyl alcohol binder. These powders and membranes were characterized by XRD, BET, and FE-SEM analysis. Hydrogen and CO gas permeation experiments were performed using Sievert's type equipment. Both fluxes on these membranes were found to decrease with increase of the temperature. This phenomenon was followed by the surface and Knudsen diffusion mechanism. The hydrogen permeability of the $La_2Ce_2O_7$ membrane was found to be $7.27{\times}10^{-5}mol/m^2sPa$, with perm-selectivity of 7.24 at 303 K.

• Preventive Nutrition and Food Science
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• v.17 no.3
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• pp.234-238
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• 2012

The volatile aroma constituents of Chrysanthemum zawadskii var. latilobum K. were separated by hydro distillation extraction (HDE) method using a Clevenger-type apparatus, and analyzed by gas chromatography-mass spectrometry (GC/MS). The yield of C. zawadskii var. latilobum K. flower essential oil (FEO) was 0.12% (w/w) and the color was light green. Fifty-five volatile chemical components, which make up 88.38% of the total aroma composition, were tentatively characterized. C. zawadskii var. latilobum K. FEOs contained 27 hydrocarbons, 12 alcohols, 7 ketones, 4 esters, 1 aldehyde, 1 amine, and 3 miscellaneous components. The major functional groups were terpene alcohol and ketone. Borneol (12.96), (${\pm}$)-7-epi-amiteol (12.60), and camphor (10.54%) were the predominant volatiles. These compounds can be used in food and pharmaceutical industries due to their active bio-functional properties.

• Journal of the Korean Applied Science and Technology
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• v.7 no.1
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• pp.71-76
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• 1990

Transesterification reactions (methyl methacrylate with monoethanolamine, methyl methacrylate with n-butyl alcohol, dimethylphthalate with ethylene glycol, dimethyl phthalate with monoethanolamine) were kinetically investigated in the presense of various metal acetate catalysts at $110^{\circ}C$. The amount of reactants was measured by gas and liquid chromatography, and the reaction rates also measured from the amount of reaction products and reactants upon each catalyst. The transesterification reactions were carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd, Maximum reaction rates were appeared at the range of 1.4 to 1.6 in electronegativity of metal ions and maximum catalytic activities were obserbed at the range of 1.5 to 1,8 in instability constant of metal acetates.

• Journal of Food Hygiene and Safety
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• v.9 no.2
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• pp.89-94
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• 1994

A simple, safe, and sensitive gas chromatographic method using packed column and electron capture detector to analyze 2, 4-D herbicide in imported lemon, grapefruit, and orange was described and its usefulness evaluated. In this scheme of analysis the acid herbicide was converted into its alkyl esters by an one-step reaction prior to analysis. The herbicide in the fruits was extracted with ethyl acetate and partitioned against dichloromethane for purification, and the extracts finished partitioning were derivatized with alcohol, using sulfuric acid as a catalyst to form the corresponding alkyl derivatives. The analytical scheme studiedwas found to be applicable for the herbicide in the fruits without a column clean-up procedure. The mean recoveries of the herbicide for lemon samples fortified at 0.1 mg/kg and 1.0 mg/kg were 93% and 95%, respectively. The detection limit was 0.5 $\mu\textrm{g}$/kg for 2.4-D methyl ester.

• Journal of the Korean Society of Tobacco Science
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• v.8 no.2
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• pp.51-66
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• 1986

Volatile aroma components, non-volatile organic acids in lamina and stems of flue-cured(NC 2326) and burley ( Burley 21) were analyzed by gas chromatography and mass spectrometry, respectively. Then compositional differences of these components between lamina and stems were discussed. The contents of volatile components were higher in flue-cured than in burley tobacco, and it was also higher in lamina then in stem. The major aroma components in lamina were neophytadiene , nicotine, solanone and benzyl alcohol but those in stems were palmitic acid, neophytadiene, nicotine, solanone and phenyl ethyl acetate. On the other hand, the contents of non-volatile organic acids were higher in burley than in flue-cured tobacco, and these values of burley tobacco were higher in lamina than in stem but flue-cured tobacco were higher in stem than in lamina. The major acids in all the above four tabacco samples were malic, citric, oxalic and linolenic acid.

• Journal of the Korean Ceramic Society
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• v.28 no.3
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• pp.197-204
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• 1991

The photoelectrochemical conversion in SnO2 films deposited by spray pyrolysis using SnCl4-alcohol solution and N2 gas has been studied. The photocurrent increases with increasing deposition temperature up to 40$0^{\circ}C$ and then decreases, and the electron affinity decreases as the deposition temperature increases to 40$0^{\circ}C$. As the concentration of the spray solution increases, the photocurrent reaches a maximum value at the concentration of 0.05M, and the electron affinity is consistent. As the thickness of the film increases, the photocurrent increases with a maximum value at the thickness of 4600$\AA$, and electron affinity does not change.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1040-1044
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• 1999

A micro porous PTFE membrane desolvator (MMD) was built and evaluated for the on-line removal of organic solvents to facilitate the determination of trace metal contaminants in the solvents by ICP-AES. Three organic solvents, isopropyl alcohol (IPA), methanol, and dimethy sulfoxide (DMSO) were studied. The MMD reduced organic solvent concentration in the sample aerosol stream by 82% to 89%, as indicated by monitoring C(I) emission. Net signal intensity of Fe, Al, and Cu was increasing with higher organic solvent concentration, with the rate of increase being solvent dependent. The signal intensities for Mg and Pb followed the trend with the C(I) signal. Changing the sweep gas flow rate affected the optimum signal intensity. Wine samples were analyzed by the method of standard addition. The concentrations of B, Al, and Mg were determined with a relative precision of less than 2.3%.

• Korean Journal of Food Science and Technology
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• v.48 no.2
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• pp.122-127
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• 2016

The objective of this study was to identify the volatile compounds and aroma-active compounds from acai berry (Euterpe oleracea). Volatiles were isolated by high vacuum distillation using solvent-assisted flavor evaporation (SAFE) and liquid-liquid continuous extraction (LLCE). To identify the characteristic aroma-active compounds of acai berry, gas chromatography-mass spectrometry-olfactometry was used. Aroma-active compounds were evaluated by aroma extract dilution analysis (AEDA). A total of 51 and 54 volatile compounds from acai berry were identified from SAFE and LLCE extracts, respectively. Alcohols were confirmed to be important volatile compounds in acai berry, as the major volatile compounds were 2-phenylethanol, (Z)-3-hexenol, and benzyl alcohol. ${\beta}-Damascenone$ (berry, rose), trans-linalool oxide (woody), (Z)-3-hexenol (grass), and 2-phenylethanol (rose, honey) were considered the aroma-active compounds in acai berry. The most intense aroma-active compound of acai berry was ${\beta}-damascenone$.