• Analytical Science and Technology
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• v.7 no.1
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• pp.25-31
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• 1994

As for analytes which did not represent the differences of the selectivity on the stationary and mobile phase, secondary chemical equilibrium theory was applied to study pH effects on the separation of alkylphenols. Mobile phase was consisted of an aqueous sodium carbonate-bicarbonate buffer and acetonitrile. The maximum selectivity for adjacent peak pairs was predicted from those values of $k^{\prime}_{HA}/k^{\prime}_{A-}$ and ${\Delta}pK$. The optimum pH determined by this method was 11.18 pH and solvent selectivity were considered at the same time to invoke the full range of selectivity effects possible for separations. Quaternary mixture composed of methanol, acetonitrile, tetrahydrofuran and water was adjusted to optimum pH 11.18. As the statistical simplex technique of an overlapping resolution map (ORM) was used to predict the optimized solvent system. The optimum solvent, which gives complete separation of alkylphenols, was determined as follws MeOH : ACN : THF = 14.4 : 81.8 : 2.8.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.1
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• pp.11-24
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• 2011

Working in a research laboratory means exposure to a wide range of hazardous substances. Several studies indicated that laboratory workers, especially working with chemicals, might have an increased risk of certain cancers. However, exposure assessment data in laboratory settings are scarce. This study was performed to examine several approaches for quantitatively assessing the exposure levels to volatile organic compounds (VOCs) among workers in chemistry laboratories. The list of 10 target VOCs, including ethanol, acetone, 2-propanol, dichlormethane, tetrahydrofuran, benzene, toluene, n-hexane, ethyl acetate, chloroform, was determined through self-administered questionnaire for six chemistry research laboratories in a university, a government-funded research institute, or private labs. From September to December 2008, 84 air samples were collected (15 area samples, 27 personal time weighted samples, 42 personal task-basis short-term samples). Real time monitors with photo ionization detector were placed during the sampling periods. In this study, benzene was observed exceeding the action levels, although all the results were below the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV). From the air sampling results, we concluded that (1) chemicals emitted during experiments could directly affect to neighbor office areas (2) chemical exposures in research laboratories showed a wide range of concentrations depending on research activities (3) area samples tended to underestimate the exposures relative to personal samples. Still, further investigation, is necessary for developing exposure assessment strategies specific to laboratories with unique exposure profiles.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.698-698
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• 2009

화력발전이 많은 비중을 차지하는 전력생산 산업은 온실가스($CO_2$)의 최대 배출 원으로 알려져 있으며 증가하는 전력 수요 뿐 만 아니라 다가오는 기후변화협약에 대응하기 위하여 $CO_2$ 회수 및 공정 개선에 관한 연구가 많이 수행되고 있다. 특히 현재 연구되고 있는 전력분야의 대표적인 $CO_2$ 회수기술은 연소 후 포집(Post-combustion capture), 순산소 연소(Oxy-fuel combustion), 연소전 탈탄소화(Pre-combustion) 3가지로 구분된다. 이중 연소전 탈탄소화 기술은 석탄가스화복합발전(IGCC) 기술과 연계하여 $CO_2$를 회수할 수 있는 방법으로 가스화 된 석탄가스에 Water-Gas Shift 반응과, $CO_2$ 분리로 얻어진 탈 탄소 연료를 통해서 전력을 생산한다. 이 기술의 핵심은 생성된 $CO_2/H_2$ 복합가스로부터 $CO_2$를 분리하는 공정으로 차세대 회수 기술로는 Membrance Reactor, SOFC, Oxygen Ion Transfer Membrane(OTM), 그리고 가스 하이드레이트가 있다. 이중 가스 하이드레이트는 $CO_2$의 회수 뿐 만 아니라 처리 기술에도 적용 가능하지만 우리나라에는 이에 관한 기술이 전무한 형편이다. 본 연구에서는 가스 하이드레이트 형성원리를 이용하여 정온 정압 조건에서 $CO_2/H_2$ 하이드레이트를 제조하였으며 특히, 하이드레이트 형성 촉진제인 THF(Tetrahydrofuran)를 첨가하여 THF 농도에 따른 상평형 및 속도론 실험을 수행 하였다. 이러한 연구는 연소전 탄소화 기술에서의 $CO_2$ 회수 분리에 대한 핵심 연구임과 동시에 탄소배출권 규제에 실질적인 기여를 할 수 있을 것으로 사료된다.

• Analytical Science and Technology
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• v.6 no.5
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• pp.453-462
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• 1993

The retention behaviors of polystyrenes influenced by mixed solvents are examined in thermal field-flow fractionation(ThFFF). Experimental data are obtained with polystyrene samples of molecular weights of 35,000, 110,000, 200,000 and 470,000 dissolved in organic solvents. The pure and mixed solvents are tetrahydrofuran(THF), chloroform(CHL), cyclohexane(CH), and benzene(BZ), respectively. The values of retention ratio(R) and thermal diffusion coefficient($D_T$) are measured with change of molecular weight and composition of mixed solvents. Atempts are then made to correlate the measured values with various physicochemical parameters of polymers and solvents. Studies suggest that R is significantly increased with the density of solvent and a good correlation is found between them. $D_T$ values decreases in the mixed solvent having has a higher concentration of poor solvent.

• Polymer(Korea)
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• v.38 no.4
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• pp.544-549
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• 2014

Double layered film consisting of polyimide/polysiloxane and interface with nano domain structure was fabricated through stepwise layer formation and subsequent aging steps. During aging of film, nano phase separation occurred between the top layer polysiloxane and the upper layer of polyimide, which was observed by transmission electron microscope (TEM). A stable and uniform polysiloxane layer was obtained, showing the reproducible pressure-sensitive adhesion (PSA) property with the peel strength of 8-13 g/inch at even $300^{\circ}C$. In addition, the resulting polymide/polysiloxane film was thermo-stable up to $435^{\circ}C$, providing the promising properties suitable for application in microelectronics processing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.316-319
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• 2000

In the case of immobilizing of glucose oxidase into polypyrrole (PPy) using electrosynthesis, the glucose oxidase (GOx) forms a coordinate bond with the polymer's backbone. However, because of intrinsic insulation and net-chain of the enzyme, the charge transfer and mass transport are obstructed during the film growth. Therefore, the film growth is dull. We synthesized the enzyme electrode by electropolymerization added some organic solvent, A formative seeds of film growth is delayed by adding the solvent. The delay is induced by radical transfer between the solvent and pyrrole monomer. In the case of adding ethanol, the radical transfer shares the contribution of dopant between electrolyte anion and GOx polyanion. This may lead to increase amount of immobilized the enzyme in ppy. However, adding tetrahydrofuran (THF), the radical transfer is more brisk, resulting in short chained polymer. Therefore, the doping level is lowered and then amount of immobilized of enzyme is decreased. For the UV absorption spectra of synthetic solution before synthesis and after, in the case of ethanol added, the optical density was slightly decreased for the GOx peaks. It suggests amount of GOx in the solution was decreased and amount of GOx in the film was increased. We established qualitatively that amount of immobilization can be improved by adding a little ethanol in the synthetic solution. It is due to radical transfer reaction. The radical transfer shares the contribution of dopant between small and fast electrolyte anion and big and slow GOx polyanion.

• Journal of the Korean Electrochemical Society
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• v.12 no.1
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• pp.54-60
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• 2009

The redox characteristics of 2-arylaldehydehydrazono-3-phenyl-5-substituted-2, 3-dihydro-1, 3, 4-thiadiazoles (1a-h) have been investigated in nonaqueous solvents such as 1, 2-dichloroethane (DCE), dichloromethane (DCM), acetonitrile (AN), Tetrahydrofuran (THF), and dimethylsulfoxide (DMSO) at platinum electrode. Through controlled potential electrolysis, the oxidation and reduction products of the investigated compounds had been separated and indentified. The redox mechanism had been suggested and proved. It had been found that all the investigated compounds were oxidized in two irreversible one-electron processes following the well-known pattern of The EC-mechanism; the first electron loss gives the corresponding cation-radical which is followed by proton removal from the ortho-position in the N-phenyl ring forming the radical. The obtained radical undergoes a second electron uptake from the nitrogen in the N = C group forming the unstable intermediate (di-radical cation) which undergoes ring closure forming the corresponding cation. The formed cation was stabilized in solution through its combination with a perchlorate anion from the medium. On the other hand, these compounds are reduced in a single two-electron process or in a successive two one-electron processes following the well known pattern of the EEC-mechanism according to the nature of the substituent; the first one gives the anion-radical followed by a second electron reduction to give the dianion which is basic enough to abstract protons from the media to saturate the (C = O) bond.

• Journal of the Korean Chemical Society
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• v.31 no.5
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• pp.419-424
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• 1987

Kinetic studies on the solvolysis of para-methyl benzyl nitrate and benzyl nitrate were carried out in aqueous methanol, ethanol, acetonitrile, acetone, tetrahydrofuran and dioxane mixtures at 60$^{\circ}$C. The rates were faster in protic solvent mixtures than in aprotic solvent mixtures. This was considered in the light of transition state stabilization by hydrogen bonding solvation of protic solvent mixtures. Grunwald-Winstein equation, extended Grunwald-Winstein equation and correlation between E$_T$(30) and rate constant were applied in order to discuss the transition state variations caused by changing benzyl substituents and solvents. The results showed that strong electrophilic assistance of solvent is operative in the the water-rich solvents.

• Textile Coloration and Finishing
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• v.30 no.3
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• pp.190-198
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• 2018

We fabricated high transmission and high scattering poly(ethylene-co-vinyl acetate)(EVA) films embedding $SiO_2$ nanoparticles to improve outcoupling efficiency in organic display. The 800nm diameter $SiO_2$ nanoparticles aggregated and formed $1.56{\mu}m$ (with ${\pm}0.853{\mu}m$ standard deviation) diameter microparticles in EVA. The total transmission of scattering film was 83.3% on Polyethylene terephthalate(PET), which was higher than reference 82.8% PET substrate. The diffuse transmission and haze of the $SiO_2$ embedded EVA film were 76.1% and 91.4%, respectively. The optimized condition was 1:1 weight ratio of $SiO_2$ nanoparticles to EVA in Tetrahydrofuran(THF) solution. When the ratio of $SiO_2$ was larger than 1, the total transmission decreased by the increase in backscattering of light due to high scattering. With the optimized condition, we could succeed to fabricate a large scale film(35m in length) with a roll-to-roll process.

• Korean journal of food and cookery science
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• v.6 no.4 s.13
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• pp.27-32
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• 1990

Lipids of Job's tears (Yullmoo) were extracted by the mixture of chloroform: methanol (2:1, v/v) and from these lipids, triglycerides were separated by column chromatography (Sephadex G-25 column) and then confirmed by thin layer chromatography (TLC) and reconfirmed by gas chromatography (GC). The triglycerides were fractionated into 6 groups on the basis of their partition numbers (PN) by reverse phase high performance liquid chromatography (HPLC) on a column Shimpack CLC-ODS using tetrahydrofuran-acetonitril (25:75) mixture as a solvent. Each of these collected fractions gave one to two peaks in the GC chromatograms according to the acyl carbon number (CN) of the triglyceride and fatty acid composition of the triglycerides were also analyzed by GC. From the results, the major triglycerides of Job's tears lipids were estimated to be C18:1 C18:2 C18:2 (OLL, 38.2%), C16:0 C18:2 C18:3 (PLLn, 15.7%), C18:1 C18:1 C18:2 (OOL, 12.6%).