• Korea-Australia Rheology Journal
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• v.16 no.4
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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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• v.16 no.4
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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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• v.32 no.3
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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.

• YAKHAK HOEJI
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• v.26 no.4
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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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• v.41 no.4
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• pp.287-292
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• 2013

Reaction of glucose and xylose to secondary hydrolysis of concentrated acid hydrolysis was quantitatively analyzed by $^1H$-NMR spectroscopic method. Anomeric hydrogen, furan and formic acid peaks were selected for quantitative analysis. The glucose was converted to the formic acid and the levulinic acid via the 5-hydroxymethylfurfural (HMF) but the xylose was converted to the fufural, which further degraded to the formic acid. The conversion to furans was slower for the glucose than the xylose. But the 5-HMF formed from the glucose was unstable in acidic aqueous medium, resulted in fast conversion to the levulinic acid and the formic acid. The furfural was relatively stable than 5-HMF at acidic aqueous medium.

• Journal of the Korean Chemical Society
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• v.38 no.5
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• pp.391-396
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• 1994

The hydrolysis of $\alpha-benzoxystyrene(1)$ in strong acidic solution has been investigated kinetically. In perchloric acid concentration lower than 5.5 M($H_o$ < -3.0), hydration paramer $\omega$ = + 7.6, and $\Phi$ = + 0.54 were obtained. The solvent isotope effect $k_{H_2O}/K_{D_2O}$ is 0.72. The substituent effect was found to conform to the Hammett $\sigma^+$ constant with $\rho$ = -0.60. On the basis of these results and other evidence, the hydrolysis of the enol ester proceeds by $A_{AL}$2 type mechanism. In concentration greater than 5.5 M($H_o$ > -3.0), isotope effect, $k_{H_2O}/_{D_2O}$ is 3.32, substituent effect, $\rho$ is -1.60 and the rate is linear with the acidity function, $H_o$. Thus, the mechanism changes one involving initial, and rate-determining olefin protonation.

• Journal of Ginseng Research
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• v.29 no.3
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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.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.3
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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.

• Journal of Powder Materials
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• v.11 no.2
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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.

• Food Science and Preservation
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• v.17 no.2
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• pp.261-266
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• 2010

Acidic hydrolysis conditions prior to HPLC analysis of plant flavonoids was investigated by response surface methodology (RSM), using leaves of Ginkgo biloba L. Ten hydrolysis conditions using 0.5-2.5 M HCl and 0.5-2.5 hr hydrolysis time were chosen to form a central composite rotatable design (CCRD), and optimization by RSM was achieved by measuring myricetin, quercetin, and kaempferol levels by HPLC. Optimum hydrolysis condition was 1.5 M HCl for 1.5 hr. The levels of flavonoids obtained under the condition were in good agreement with predicted maximum values, with yields of more than 95%. These optimum hydrolysis condition was applied to analysis of flavonoid content in the leaves of Camellia sinensis, Ficus carica, and Sageretia theezans.