• Bulletin of the Korean Chemical Society
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• 제20권5호
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• pp.573-576
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• 1999

The rate constants and kinetic solvent isotope effects (KSIE, KMeOH/kMeOD) for solvolyses of para-substituted phenylchloroformates in CH3OH, CH3OD, H2O, D2O, 50% D2O-CH3OD were determined at 15.0 and 25.0℃ using conductometric method. Kinetic solvent isotope effects for the solvolyses of para-substituted phenyl chloroformates were 2.39-2.51, 2.21-2.28, and 1.67-1.69 for methanol, 50% aqueous methanol, and water, respectively. The slopes of Hammett plot for solvolysis of para-substituted phenyl chloroformates in methanol, 50% aqueous methanol, and water were 1.49, 1.17 and 0.89, respectively. The Hammett type plot of KSIE, log (KSIE) versus p, can be a useful mechanistic tool for solvolytic reactions. The slopes of such straight lines for para-substituted phenyl chloroformates are almost zero in methanol, 50% aqueous methanol, and water. It was shown that the reaction proceeds via an associative SN2 and/or general base catalysis addition-elimination (SAN) mechanism based on activation parameters, Hammett p values, and slopes of Hammett type plot of KS-IE.

• 한국응용과학기술학회지
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• 제41권2호
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• pp.520-529
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• 2024

Lycium barbarum extract has a high potential to be developed as a health functional food due to the various health-promoting effects of Lycium barbarum. This study analyzed changes in nutritional and functional components depending on the extraction solvent (purified water and a mixture of purified water and alcohol) and the condition of the sample. The nutritional components (carbohydrates, protein, fat, ash), organic acids, amino acids, total phenolic compounds, and total flavonoids of the extract produced during the extraction process were analyzed. The nutritional composition and functional substances of the extracts showed some differences depending on the type of solvent and the condition of the sample. The amounts of crude protein (7.61%), crude fat (1.63%), carbohydrate (90.22%), and ash (0.54%) of dried Lycium barbarum extract using purified water as a solvent were similar to those of the powder sample extract. The highest content of citric acid was 4.31 mg/mL, similar to the case of acetic acid, when the powder sample used a mixture of purified water and alcohol as a solvent. The highest amino acid content was 357.39 mg/mL when the powder sample was mixed with purified water and alcohol as a solvent. The total amount of phenolic compounds was 686.16 g/L when the powder sample was extracted with a mixture of purified water and alcohol as a solvent. The highest total flavonoid content was 111.32 g/L when the powder sample was extracted with a mixture of purified water and alcohol as a solvent.

• Mass Spectrometry Letters
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• 제8권2호
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• pp.29-33
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• 2017

Understanding the mechanisms that control and concentrate the observed electrospray ionisation (ESI) response from peptides is important. Controlling these mechanisms can improve signal-to-noise ratio in the mass spectrum, and enhances the generation of intact ions, and thus, improves the detection of peptides when analysing mixtures. The effects of different mixtures of aqueous: organic solvents (25, 50, 75%; v/v): formic acid solution (at pH 3.26) compositions on the ESI response and charge-state distribution (CSD) during mass spectrometry (MS) were determined in a group of biologically active peptides (molecular wt range 1.3 - 3.3 kDa). The ESI response is dependent on type of organic solvent in the mobile phase mixture and therefore, solvent choice affects optimal ion intensities. As expected, intact peptide ions gave a more intense ESI signal in polar protic solvent mixtures than in the low polarity solvent. However, for four out of the five analysed peptides, neither the ESI response nor the CSD were affected by the volatility of the solvent mixture. Therefore, in solvent mixtures, as the composition changes during the evaporation processes, the $pK_b$ of the amino acid composition is a better predictor of multiple charging of the peptides.

• 약학회지
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• 제45권6호
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• pp.623-633
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• 2001

Various bupivacaine-loaded microspheres were prepared using poly(d,1-lactide) (PLA) and poly(d,1-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. The effects of process conditions such as drug loading, polymer type and solvent type on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency and yield of PLGA micro- spheres were higher than those of PLA microspheres. The prepared microspheres had an average particle size below 5${\mu}{\textrm}{m}$. The particle size range of microspheres was 1.65~2.24${\mu}{\textrm}{m}$. As a result of SEM, the particle size of PLA microspheres was smaller than that of PLGA microspheres. In morphology studies, microspheres showed a spherical shape and smooth surface in all process conditions. In thermal analysis, bupivacaine-loaded microspheres showed no peaks originating from bupivacaine. This suggested that bupivacaine base was molecular-dispersed in the polymer matrix of microspheres. The release pattern of the drug from microspheres was evaluated for 96 hours. The initial burst release of bupivacaine base decreased with increasing the molecular weight of PLGA, and the drug from microspheres released slowly. In conclusion, bupivacaine-loaded microspheres were successfully prepared from poly(d,1-lactide) and poly (d,1- lactic-co-glycolide) polymers with different molecular weights allowing control of the release rate.

• 대한화학회지
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• 제30권1호
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• pp.3-8
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• 1986

물-글리세롤, 물-에틸렌 글리콜, 물-이소프로필 알코올 및 물-t-부틸 알코올의 2성분 혼합용매 중에서 cis-$[Co(en)_2ClNO_2]^+$착이온의 가용매 분해반응을 분광광도법으로 연구하였다. 용매의 극성이 커짐에 따라 반응속도도 커지는 경향이 있었으며 반응속도의 대수값과 $\frac{D-1}{2D+1}$값을 도시한 결과 비직선적인 관계를 나타내는 것으로 보아서 용매의 수소결합이나 분산력등의 비정전기적인 상호작용이 지배적으로 작용함을 알 수 있었다. log k와 Grundwald-Winstein의 Y값을 도시한 직선의 기울기와 Kivinen식에서 구한 전이상태에 관여하는 물분자의 수 n값으로부터 실험에 사용한 착물의 가용매 분해반응은 Id메카니즘으로 진행됨을 알았다. 한편 자유에너지 사이클의 결과는 초기상태에서 보다 전이상태에서 용매구조의 효과가 더 큼을 알 수 있었다.

• 한국인쇄학회지
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• 제31권1호
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• pp.15-37
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• 2013

Split digital printing into interior and outdoors on present advertisement. When is printing machine for interior mainly, use ink of water-based type. Equipment of this type embodies high resolution, but ink special quality light stability is weak. Also, when is printing machine for outdoors, printing machines of solvent or UV type are used because of water resistance and light stability. This printing machines hard to embody ink special quality high resolution mainly. And because outside is far visibility range, is uncommon in case high resolution requires embodiment. Therefore, high resolution of inside is water-based type considering this item and outside printing machine of low resolution solvent type mainly announce. Also, divide into eco-friendly latex ink type that is announced to water-based, solvent, UV according to ink type and the latest market using in occasion of digital printing machine used as advertisement industry. Color management that is been consistent of original image has a lot of difficulties by using substrate that is also various to digital printing machine for such various advertisement. But, consumers is rising realization about color or desire about quality improvement of color gradually in interior outside advertisement market. So, require solution method. Therefore, in this paper, eco-friendly ink use applied device calibration through linearization in done latex digital printing machine to basis. And studied right color management plan of digital printing for interior outside advertisement through three steps such as G7 calibration application and ICC profile application.

• 한국산업보건학회지
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• 제15권1호
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• pp.19-26
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• 2005

In previous report, we presented that petroleum based solvents used in dry cleaning shop was almost similar to stoddard solvent defined by ACGIH and NIOSH, and the occupational exposure standard of stoddard solvent could be used in total exposure assessment of those solvents. The specific aim of the this study was to evaluate of the solvent exposure used in commercial dry cleaning shops by using occupational exposure standard of stoddard solvent. We conducted first survey of 8 self-employed dry cleaning shops and 5 factory type dry cleaning shops from July to August, and second survey of the same shops from October to November in 2002. The exposure concentration to the solvent during loading and unloading activity of vented dry cleaning machine was 489.2ppm(GM), 270.3ppm(GM), respectively, which was almost excursion limit(500ppm) of ACGIH, and exceed the ceiling limit(312ppm) of NIOSH. The time-weighted average (TWA) worker exposure to the solvent was 21.3ppm(GM) at self-employed shops, 20.7ppm(GM) at factory type shops on first survey, and 31.1ppm(GM), 33.7ppm(GM), respectively on second survey. The TWA exposure concentration of workers with spotting and cleaning machine operating job was 25.4ppm(GM), which was 2.9 times higher than the TWA exposure concentration, 8.8ppm(GM) of press workers. All TWA exposure concentrations was lower than OEL(100ppm) of stoddard solvent. We found that the most heavy exposure process at dry cleaning was loading, unloading process, and the vent of dry cleaning machine was the main emission source for workers exposure to petroleum based solvent.

• Bulletin of the Korean Chemical Society
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• 제19권10호
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• pp.1036-1042
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• 1998

The preconcentration and determination of trace elements in water samples were studied by a solvent sublation utilizing dithizonate complexation. After metal dithizonates were formed, trace amounts of cadmium, cobalt, copper and lead were floated and extracted into small volume of a water-immiscible organic solvent on the surface of sample solution and determined in the solvent directly by GF-AAS. Several experimental conditions as formation condition of metal-dithizonate complexes, pH of solution, amount of dithizone, stirring time, the type and amount of surfactants, N2 bubbling rate and so on were optimized for the complete formation and effective flotation of the complexes. And also four kinds of light solvents were compared each other to extract the floated complexes, effectively. After the pH was adjusted to 4.0 with 5 M HNO3, 8.0 mL of 0.05% acetone solution of dithizone was added to 1.00 L water sample. The dithizonate complexes were flotated and extracted into the upper methyl isobutylketone (MIBK) layer by the addition of 2.0 mL 0.2% ethanolic sodium lauryl sulfate solution and with the aid of small nitrogen gas bubbles. And this solvent sublation method was applied to the analysis of real water samples and good results of more than 85% recoveries were obtained in spiked samples.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2007년도 춘계학술대회논문집
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• pp.380-390
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• 2007

The purpose of this study is to make a functional Hanji treated with an oriental lacquer which has various functionalities. The raw oriental lacquer produced in China was used in this study This lacquer was diluted with ethanol and terpene in different solvent ratios. The diluted lacquer in the solvents had two layers. The upper layer was solvent soluble and the lower contained precipitates. Hanji was treated with the solvent solubles and the mixture containing precipitates, and then properties of the Hanji were evaluated. The oriental lacquer consisted of 25.04% of water, 60% of urushiol, 3.13% of nitrogen-containing compounds, and 5.66% of gum. The pH of oriental lacquer was 5.3 and the viscosity was 1680 cP. The average weight, thickness, and density of Hanji treated with oriental lacquer tended to gradually decreased as the lower concentration of lacquer was used and as the solvent soluble was treated. Tensile strength of the treated Hanji decreased when the diluted lacquer was used and Hanji treated with terpene dilutes at the ratio of lacquer to solvent of 1:5 (v/v) showed higher tensile strength than ones treated with ethanol dilutes. The folding endurance decreased as the less concentrated lacquer was used and the highest value was obtained when 1:40 (v/v) of lacquer to solvent ratio in both ethanol and terpene mixture. Absorption ratio was higher in the Hanji treated with ethanol mixture, treated with the lacquer in higher concentration, and treated with ethanol mixture. Hanji treated with ethanol dilutes at 1:20 (v/v) and the lower ratio of lacquer to solvent showed a hydrophobic property. Amount of the bound dye materials tended to be decreasing as the concentration of lacquer becomes lower and it was higher in Hanji treated with ethanol mixture than with terpene mixture. Color of Hanji treated with the solvent diluted mixture was Y to YR-type, whereas that of Hanji treated with raw oriental lacquer was Y-type, terpene

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.99-103
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• 2008

Solvent extraction using salphen as a ligand has been investigated for the selective separation and determination of trace Fe(II) and Fe(III). A salphen ligand was synthesized, and solvent extraction variables, such as solution pH, the concentration of salphen, the type of organic solvent, auxiliary agents, oxidants and the effect of interference were optimized. Salphen is stable at pH 3-4, and Fe(III)-salphen complexes can be selectively extracted into an MIBK(4-methyl-2-pentanone) phase from an aqueous solution within this pH range. For the determination of the total amount of iron in 100 mL of aqueous solution, Fe(II) ions were completely oxidized using 0.05 mL of 3.5% H2O2 without side reactions. To evaluate its applicability, the proposed method was applied to determine trace Fe(II) and Fe(III) in several kinds of water samples. Reproducible results were obtained with RSD of less than 3.0%, and the recoveries for this reliability were obtained with 91-112%.