• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.175-182
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• 2004

Colloidal coating solution was prepared to enhance the hydrophilic property of the film surface. Water and ethanol were used as the dispersion media and (glycidoxypropyl) trimethoxysilane (GPS) as a binder in the colloidal silica coatings. Ethylene diamine was added to the colloidal silica solution as the curing agent. The colloidal silica solution was regarded as a hard-sphere suspension model with low volume fraction of the silica particles. Rheological properties of the silica suspensions modified with GPS have been investigated as a function of pH and concentration. The acidic solution showed high viscosity change by fast hydrolysis reaction and adsorption of the organic binders on the surface of silica particles. However, the hydrolysis was slow at the basic condition and the binders combined with themselves by condensation. The viscosity change was smallest at pH 7. The viscosity increased with the curing time after adding ethylenediamine, and the increase of viscosity at low pH was higher than that at high pH. The hydrophilic properties of the coating film were investigated by the contact angle of water and film surface. The smallest contact angle was shown under the strong acidic condition of pH 2.

• Food Science and Biotechnology
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• 제16권4호
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• pp.543-548
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• 2007

Low-energy processing technology, which enhances the utility of defatted soybean flour (DSF), was developed using extrusion processing. DSF was extruded at different conditions using a twin screw extruder and then, dried at $40^{\circ}C$ for 20 hr. The nitrogen solubility index (NSI), viscosity, water solubility index (WSI), and water absorption index (WAI) of DSF increased after extrusion processing. The density of DSF extrudates decreased with the decrease in water content from 53 to 33% and the increase in extrusion temperature from 110 to $160^{\circ}C$. The addition of NaOH from 1.2 to 1.8% and citric acid from 1 to 5% increased the total solubility (TS) of DSF due to the decrease of protein coiling and hydrophobic bonds formation during extrusion processing. When viscozyme was reacted first, TS, NSI, and soluble carbohydrate content of DSF hydrolysates increased about 12, 6, and 7%, respectively, compared to them reacted with protease first. The TS and NSI of DSF hydrolysates were increased about 15 and 10%, respectively, by extrusion processing at alkaline and acidic pH. Extrusion processing at alkaline and acidic pH contributed the increase of efficiency to hydrolyze DSF samples using enzyme.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.809-814
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• 2011

A method based on the TMS derivatives and acidic hydrolysis was developed for the simultaneous determination of free and conjugated steroidal hormones in surface water. A silylation of five natural and two synthetic steroidal hormones was achieved with N-methyl-N-(trimethylsilyl) trifluoroacetamide/$NH_4I$ (1000:3) under catalysis of dithioerythritol for 60 min at $80^{\circ}C$. TMS derivatives of the steroid hormones containing multifunctional groups offer a single derivative product under this condition. The accuracy of the analytes was in the range of 87 to 110% at a concentration of 20 and 50 ng/L with relative standard deviations of less than 10%. The method detection limit was in the range of 0.01 to 0.02 ng/L for surface water. Natural steroidal hormones were detected in a concentration range of 0 to 1.03 ng/L in free form and 0 to 14.6 ng/L in conjugated form, respectively. We found that most of the natural hormonal steroids exist in conjugate forms (43 to 100%) in river water.

• 약학회지
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• 제26권4호
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• pp.223-229
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• 1982

Uremia is associated with defective protein binding of weakly acidic drugs, whereas the protein binding of basic drugs tends to be normal. The exact chemical nature of compound(s) and mechanism for these changes as yet is unknown, and has not been defined. Organic solvent extraction of pooled normal human urine following hydrolysis by hydrochloric acid produced an extract, which when added to normal human serum, was capable of inducing binding defects similar to those in uremia. Binding defects were observed with the weakly acidic drugs such as nafcillin, salicylate, sulfamethoxazole and phenytoin while the binding of the basic drugs such as trimethoprim and quinidine were unaffected. The binding defects induced by the hydrolyzed urine extract could readily be corrected by same organic solvent extraction of acidified serum and the defects could be transferred to the normal human serum using the organic solvent layer at the physiologic pH (7.4). Followed by reacidification ind extraction of the binding defects induced serum with the same solvent, separated several fractions were obtained on thin-layer chromatography. One of these fractions could reinduce the binding defects and this factor(s) is apparently weakly acidic compounds and tightly bound to serum at physiologic pH, but extractable at acidic pH, and its molecular weight range is approximately 500 or less similar to those seen in uremia. These findings strongly support the hypothesis that the drug binding defect in uremia is due to the accumulation of endogenous metabolic products which arc normally excreted by the kidneys but accumulate in renal failure.

• Journal of the Korean Wood Science and Technology
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• 제41권4호
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• pp.287-292
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• 2013

진한 산 가수분해 반응 중 2차 가수분해 조건에서 포도당과 자일로스의 반응을 수소 핵자기 공명 분광분석을 통하여 정량적으로 분석하였다. 정량분석은 아노머성 수소, 퓨란과 개미산의 특징적인 피크를 이용하여 실시하였다. 진한 산 가수분해의 2차 가수분해 조건에서 포도당의 일부가 5-hydroxymethylfufural (5-HMF) 중간 구조를 거쳐 levulinic acid와 개미산으로 분해되었음을 확인하였다. 자일로스는 furfural 중간 구조를 거쳐 개미산으로 분해가 되었으며, 포도당은 자일로스보다 2차 가수분해 조건에서 산에 의한 퓨란계 화합물의 전이가 느리게 전환되어 단당의 안정성이 높았다. 퓨란계 화합물로 전환된 이후, 산에 민감한 5-HMF는 쉽게 formic acid와 levulinic acid로 전환되었지만, furfural은 formic acid로의 분해 반응이 더디게 진행되어 furfural의 농도가 5-HMF보다 상대적으로 높게 나타났다.

• 대한화학회지
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• 제38권5호
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• pp.391-396
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• 1994

강산성 용액에서 $\alpha$-벤족시스티렌(1)의 가수분해를 속도론적으로 다루었다. 과염소산이 5.5M보다 낮은 농도($H_o$ < -3.0)에서 수화파라메타 $\omega$ = + 7.6, $\Phi$ = + 0.54를 얻었다. 용매동위원소효과 $k_{H_2O}/k_{D_2O}$는 0.72였고, Hammett $\sigma^+$ 상수에 대한 치환기 효과 $\rho$ = -0.60이었다. 이 결과와 다른 증거로부터 이 산도 범위에서 엔올에스테르의 가수분해는 $A_{AL}$2 형태의 메카니즘에 의해 진행되었다. 과염소산 농도가 5.5 M 이상에서는 동위원소효과, $k_{H_2O}/_{D_2O}$는 3.32이었고, 치환기 효과, $\rho$=-1.6이었으며, 속도상수는 산도함수, $H_o$에 비례하였다. 따라서 반응메카니즘은 변하여 올레핀이 양성자화되는 첫단계가 속도결정단계가 된다.

• Journal of Ginseng Research
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• 제29권3호
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• pp.126-130
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• 2005

Ginseng saponins have been known as main active principles and are quantified as the index components of ginseng and its products for quality control. However ginseng saponins are easily hydrolyzed in acidic solutions of crude drug preparations. Due to the hydrolysis of saponins in acidic condition, it is generally difficult to determine ginseng saponins In crude drug preparations. Ginseng saponins, prosapogenins and sapogenins of crude drug extracts were quantified by HPLC. Ginseng saponins were quantified by HPLC on $Lichrosorb-NH_2$ column with acetonitrile/water/1-butanol(80:20:10, v/v). Ginseng $prosapogenin-Rg_2$ and $-Rg_2$ were extracted with ethyl acetate from $50\%$ acetic acid hydrolyzates of saponin fractions and quantified by HPLC on $Lichrosorb-NH_2$ column with acetonitrile/water(90:10, v/v). Ginseng sapogenins, panafadiol and panaxatriol, were extracted with diethyl ether from $7\%-sulfuric$ acid hydrolyzates of saponin fractions and quantified by HPLC on ${\mu}-Bondapak\;C_{18}$ column with acetonitrile/methano1/chloroform(83:10:7, v/v). These methods of analyses of sapogenins and prosapogenins were more useful for quality control than those of ginseng saponins in some of crude drug preparations.

• 펄프종이기술
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• 제44권3호
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• pp.9-14
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• 2012

Formed fermentation inhibitors during acid saccharification leads to poor alcohol production based on lignocellulosic bio-alcohol production process. In this work, it is focused on the formation of fermentation inhibitors from xylan, which is influenced by reaction tempearature and time of acidic sacharifiaction of xylose and glucuronic acid. In second step of concentrated acid hydrolysis, part of xylose and glucuronic acid was converted to furfuraldehyde and formic acid by dehydration and rearrangement reactions. Furfural was form from xylose, which was highly sensitive to reaction temperature. Formic acid was come from both xylose and glucuronic acid, which supposed to main inhibitor in biobutanol fermentation. Reaction temperature of second hydrolysis was main variables to control the furfural and formic acid generation. Careful control of acid saccharification can reduce generation of harmful inhibitors, especially second step of concentrated sulfuric acid hydrolysis process.

• 한국분말재료학회지
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• 제11권2호
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• pp.118-123
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• 2004

A formation of aluminum hydroxide by hydrolysis reaction in the water has been studied by using nano aluminum powder fabricated by pulsed wire evaporation(PWE) method. The hydroxide type and morphology depending on temperature and pH were examined by structural analysis. The Boehmite($Al_2O_3$.$H_2O$ or AIO(OH)) was predominantly formed in high temperature region over 4$0^{\circ}C$, while the Bayerite($Al_2O_3$.$H_2O$ or $Al(OH)_3$) below $30^{\circ}C$ of hydrolysis temperature. The Boehmite formation was preferred to the Bayerite in acidic solution in the same hydrolysis temperature. The slowly formed Bayerite phase showed facet crystalline structure, while the fast formed Boehmite was fine fiber with a large aspect ratio of several nm in diameter and several hundred nm in length, and with much larger specific surface area(SSA) than that of Bayerite. The highest SSA was about $420m^2$/g.

• 한국식품저장유통학회지
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• 제17권2호
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• pp.261-266
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• 2010

식물체의 플라보노이드 성분 함량 분석에 필요한 적정 가수분해 조건을 구명하기 위하여 은행잎을 이용하여 중심합성법으로 설계한 산 가수분해 시간과 HCl 농도에 따라 myricetin, quercetin, kaempferol 함량을 HPLC로 분석하고, SAS의 반응표면분석법으로 산 가수분해 조건의 최적화를 시도하였다. HCl 0.5~2.5 M, 0.5~2.5시간 범위 내에서 10개의 구간을 잡아서 최적화한 결과 1.5~1.9 M의 HCl 농도와 1.4~2.0시간의 가수분해 조건에서 myricetin, quercetin, kaempferol 성분이 가장 높았다. Superimposing하여 구한 식물체의 플라보노이드의 적정 가수분해 조건은 HCl 1.5 M, 1.5시간이었으며, 이 조건에서 구한 플라보노이드 함량의 예측치와 측정치는 95% 이상 일치하였다. 본 연구에서 구한 적정 가수분해 조건을 이용하여 녹차잎, 무화과잎, 상동나무잎의 플라보노이드 함량을 분석하여 보았다.