• 한국산업보건학회지
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• 제6권2호
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• pp.209-221
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• 1996

The purpose of this study was to find a suitable cosolvent to $CS_2$ so that desorption efficiency can be improved for both polar and non-polar organic solvent mixtures collected on an activated charcoal tube. Cosolvents added to $CS_2$ include: DMF(N,N-dimethylformamide): $CS_2$ (v/v 1:99), DMF:$CS_2$(v/v 3:97), BC (butyl carbitol, 2-(2-butoxy ethoxy) ethanol):$CS_2$(v/v 1:99), and BC:$CS_2$(v/v 3:97)). The results obtained were as follows : 1. Comparing the desorption efficiency of $CS_2$ with those of $CS_2$ with 1, 3, 5 % DMF and 1, 3 % BC cosolvents for two different groups of charcoal tubes each containing 8 different polar and non-polar organic solvents with 3 different concentration levels, the desorption efficiencies of the cosolvent-added $CS_2$ increased significantly for all polar organic solvents regardless of concentration levels tested. For non-polar organic solvents, no noticeable improvement was detected except xylene and trichloroethylene. The desorption efficiency of xylene increased significantly while that of trichloroethylene increased significantly at the lowest concentration level tested. 2. Either 5 % DMF or 3 % BC was the most suitable cosolvent because the desorption efficiency for non-polar organic solvent mixtures was similar or slightly improved compared with that of $CS_2$, while those of for polar organic solvent mixtures were above 75 % except for cyclohexanone. 3. The smallest variations in desorption efficiency represented by the ratio calculated from the maximum to minimum desorption efficiency for all concentration levels tested were found when 3 % BC was used as a cosolvent. The above results indicate that the desorption efficiency of $CS_2$ particularly for polar organic solvent mixtures collected on a charcoal tube can be significantly improved by the use of cosolvents such as 5 % DMF or 3 % BC. A caution, however, is in order for selecting a cosolvent whenever the cosolvent itself is being used in the workplace or the impurities contained in the cosolvent may interfere with the analytical results. In addition, to improve desorption efficiencies for such organic solvents as cyclohexanone or ketones, it is recommended to use suitable collection and desorption media other than the traditional method of charcoal tube collection/$CS_2$ desorption.

• 한국산업보건학회지
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• 제7권1호
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• pp.3-18
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• 1997

This study was conducted to evaluate desorption efficiencies by types of desorption solvent for polar and non-polar organic compounds collected on activated charcoal tubes. Analytes tested were toluene, m-xylene, isobutyl alcohol, n-butyl alcohol, cellosolve acetate, and butyl cellosolve. Three different concentration levels of spiked sample were made. Types of cosolvent mixed with the main solvent, $CS_2$, were methanol, pentanol, and dimethylformamide (DMF) and the cosolvent for methylenechloride was methanol. The amounts of cosolvent added to the main solvent were 1, 5, and 10% by volume (v/v%), respectively. The results were as follows: 1. For all mixed solvents except 1% methanol and 1% pentanol with $CS_2$, desorption efficiency significantly increased, compared with that of $CS_2$ alone. 2. Desorption efficiency increased by increasing analyte loading on charcoal tube regardless of mixed solvents used and the material polarity. 3. For all cosolvents mixed with $CS_2$ by 1% and 5% volume, desorption efficiency for non-polar compound was significantly higher than that of polar compound. For the 10% mixed solvents and the methylenechloride mixed with methanol, the results were opposite. 4. The lowest mean percent bias of 4.79% was obtained from the 5% DMF-$CS_2$ mixed solvent, followed by 4.82% from the 10% DMF-$CS_2$ solvent while the highest bias of 23.26% was from the solvent of $CS_2$ alone. Based on the results of this study, in order to increase desorption efficiency, it is recommended to add such cosolvents as methanol, pentanol, and DMF to $CS_2$, preferably 5% by volume for analyzing polar compounds collected in charcoal tubes.

• 한국분말재료학회지
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• 제10권1호
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• pp.6-14
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• 2003

The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical $CO_2$ debinding by using cosolvent or binary mixture of propane + $CO_2$. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical $CO_2$. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical $CO_2$ debinding, second method is to use mixture of supercritical propane + $CO_2$, as solvent. In case of using mixture of supercritical propane + $CO_2$, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + $CO_2$ for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical $CO_2$.

• KSBB Journal
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• 제18권5호
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• pp.385-392
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• 2003

초임계 이산화탄소를 이용한 효율적인 DDS 설계를 위한 기초연구로서 순수한 초임계 이산화탄소와 초임계 이산화탄소와 상용성이 있으면서 고분자에 대해서는 비용매로 작용하는 극성 공용매로 변형된 초임계 이산화탄소를 이용하여 생체분해성 고분자인 L-PLA의 미세입자 형성에 대하여 고찰하였다. L-PLA용액의 농도가 증가할수록 입자 크기는 증가하였으며, 약 4%이상의 농도에서는 입자들 간의 강한 응집으로 인하여 입자의 형태가 구형에서 섬유상으로 변화하였다. 침전기 내 초임계 유체의 온도가 높아짐에 따라 생성된 입자의 크기가 증가하였으며, 온도가 높아질수록 입자의 분포는 불균일하게 나타났다. 용액 유량이 증가함에 따라 전체적으로 구형 입자의 생성이 증가하였으며, 입자의 평균 크기는 증가하는 것으로 나타났다. 순수한 초임계 이산화탄소를 사용한 경우 모든 실험 조건에서 입자 회수율은 약 30∼40% 정도로 나타났다. 입자 회수율을 향상시키기 위해 극성 공용매를 초임계 이산화탄소와 혼합하여 입자를 제조하였다. 메탄올과 에탄올을 이산화탄소 대비 몰비 0.5로 혼합한 경우 회수율은 각각 80%와 70%로 매우 높은 값을 나타냈으며, 평균 직경 1 $\mu\textrm{m}$이하의 매우 작은 입자를 제조할 수 있었다.

• 공업화학
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• 제1권1호
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• pp.73-82
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• 1990

로진과 말레산무수물로부터 rosin-maleic anhydride adduct (RMA)를 합성하고 이를 방향족디이소시아네이트와 반응시켜서 폴리아미드이미드를 합성하였다. 반응촉매로는 Sodium methoxide ($CH_3ONa$)를 사용하였고 반응용제로는 N-메틸-2-피롤리돈 (이하 NMP)을 사용하였다. NMP는 방향족디이소시아네이트와 부반응을 하기 때문에 중합체의 수율과 점성도가 낮았다. 부반응을 줄이기 위하여 NMP에 방향족용제인 크실렌, 아세토페논, 벤조니트릴 및 니트로벤젠을 공용제로 혼합, 사용하였다. 극성이 비교적 작은 공용제의 혼합시 공용제 혼합비율이 60%인 경우 약 70%정도, 극성이 비교적 큰 공용제의 혼합계에서는 혼합비율이 40%인 경우 90% 이상의 수율로서 높은 수율을 얻을 수 있었다. 중합체는 무정형이거나 약간의 결정성을 갖는 구조였으며 고극성용제에서만 용해하였다. 중합체의 점성도는 0.12-0.26dl/g의 범위였다. 열분석 결과 중합체의 초기분해온도는 $330^{\circ}C$ 이상으로서 양호한 열안정성을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2689-2694
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• 2011

Novel 5'-norcarbocyclic adenine and guanine phosphonic acid analogues with 6'-electronegative moiety such as unsaturated C-C bond were designed and synthesized from commercially available 2-methylene-propane-1,3-diol (4). Regioselective Mitsunobu reaction successfully proceeded from an allylic functional group (${\pm}$)-12b at low reaction temperature in polar cosolvent (DMF/1,4-dioxane) to give purine phosphonate analogues (${\pm}$)-13 and (${\pm}$)-20. The purine nucleoside phosphonate and phosphonic acid analogues were subjected to antiviral screening against HIV-1. Guanine analogue (${\pm}$)-23 shows significant anti-HIV activity in PBM cell lines ($EC_{50}=8.1\;{\mu}M$).

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1440-1448
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• 2014

Co(II)-tetrasulfonated phthalocyanine (CoTSP) is known to be aggregated to dimer at high concentration levels in water. A study on the aggregation of CoTSP using multivariate curve resolution analysis of the visible absorbance spectra over a concentration range of 30, 40 and 50 ${\mu}M$ in the presence of dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), acetonitrile (AN) and ethanol (EtOH) in the concentration range of 0 to 3.57 M is conducted. A hard modeling-based multivariate curve resolution method was applied to determine the dissociation constants of the CoTSP aggregates at various temperatures ranging from 25, 45 and $65^{\circ}C$ and in the presence of various co-solvents. Dissociation constant for aggregation was increased and then decrease by temperature and concentration of phthalocyanine, respectively. Utilizing the vant Hoff relation, the enthalpy and entropy of the dissociation equilibriums were calculated. For the dissociation of both aggregates, the enthalpy and entropy changes were positive and negative, respectively. Molecular dynamics simulation of cosolvent effect on CoTSP aggregation was done to confirm spectroscopy results. Results of radial distribution function (RDF), root mean square deviation (RMSD) and distance curves confirmed more effect of polar solvent to decrease monomer formation.