• Journal of the Korean Chemical Society
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• v.40 no.7
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• pp.492-500
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• 1996

The solvent extraction of trace Bi, Cd and In in seawater samples using ammonium pyrrolidine dithiocarbamate(APDC) as a complexing agent was studied. The pH of sample solution, the amount of APDC, the type of solvent and the shaking time were investigated together with back-extraction conditions. After the pH of 200 mL seawater was adjusted to 4.0 and 5.0 mL of 1% APDC was added, analytes were extracted with 10.0 mL of MIBK by shaking for 35 minutes. The organic phase seperated was washed with a 0.05 M NaOH 10.0 mL to remove HPDC. The analytes were stripped by the back-extraction of 5 minute shaking with 5 mL of 4 M HNO3 containing 150 ㎍/mL Pd(Ⅱ). Detection limits of Bi, Cd and In were 0.038, 0.0057 and 0.023 ng/mL, respectively. Both of Bi(Ⅲ) and In(Ⅲ) were not detected in two kinds of water samples of the East Sea and the contents of Cd(Ⅱ) were 0.018 and 0.016 ng/mL. The recoveries of over 90% showed that this procedure was applicable to the determination of such trace elements in seawater samples.

• Korean Journal of Food Science and Technology
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• v.32 no.1
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• pp.1-8
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• 2000

Fifty-seven extracts from flower, leaf and stem of Agastache rugosa O. Kuntze were prepared by varing extraction conditions: solvents (hot water, ethanol and NaCl solution); temp.$(60,\;80\;and\;100^{\circ}C)$ and solvent ratios (10 to 35 times per material). Lipid content of leaf was 9.54% and protein content of the flower where the essential amino acids were most abundant among all parts was 16.8%. Among six minerals (Na. Ca, Fe, P, K and Mg) detected from all parts of the plant, the content of K was the highest. Extraction yield rated higher in odor of water, ethanol and NaCl solution, respectively and the extractions reached eqilibrium in about 15 to 20 min, regardless of extraction conditions. pH values of all extracted solvents maintained neutral upon extraction and a few free sugars in forms of glucose and fructose were detected from ethanol extracts. Colors and organoleptic characteristics of the extracts which determine the properties of final products varied with extraction conditions.

• Korean Journal of Food Science and Technology
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• v.34 no.2
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• pp.174-179
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• 2002

A simple and sensitive analysis method based on reverse phase (RP) HPCL with flourescence detector was developed for simultaneous determination of bisphenol A (BPA), bisphenol F (BPF), bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE), and their degradation products, $BADGE{\cdot}H_2O$, $BADGE{\cdot}2H_2O$, $BFDGE{\cdot}H_2O$, $BFDGE{\cdot}2H_2O$, $BADGE{\cdot}HCl{\cdot}H_2O$, $BADGE{\cdot}HCl$, $BADGE{\cdot}2HCl$, $BFDGE{\cdot}HCl{\cdot}H_2O$, $BFDGE{\cdot}HCl$ and $BFDGE{\cdot}2HCl$, which were hydrolyzed and chlorinated forms of BADGE and BFDGE, in canned foods and food simulants. These compounds were identified by GC/MSD with $MSTFA-NH_4I-DTE$ derivatization. Recovery study was performed at each 100 ng/mL levels of BPA, BPF, BADGE and BFDGE added to canned foods and food simulants. This method was resulted in recovery of $90{\sim}114%$ with relative standard deviation of $4.1{\sim}7.0%$, detection limits of $6{\sim}11$ ng/mL and quantitation limits of $12{\sim}18\;ng/mL$. Calibration curves were linear with correlatin coefficients of 0.997 for BPF, 0.996 for BPA, 0.9987 for BFDGE, and 0.9989 for BADGE.

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.346-353
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• 2011

Base hydrolysis of 7-hydroxy-2H-chromen-2-one (HC) and 7-hydroxy-2H-chromen-2-one-4-acetic acid (HCA) in aqueous-methanol and aqueous-acetone mixtures were studied kinetically at temperature range from 283 to 313 K. The activation parameters of the reactions were evaluated and discussed. Moreover, the change in the activation energy barrier of the investigated compounds from water to water-methanol and water-acetone mixtures was estimated from the kinetic data. It is observed that the change in activation barriers is more or less the same for the hydrolysis of HC and HCA. Base hydrolysis of HC and HCA follows a rate law with $k_{obs}=k_2[OH^-]$. The decrease in the rate constants of HC and HCA as the proportion of methanol or acetone increases is due to the destabilization of $OH^-$ ion. The high negative values of entropy of activation support the proposal mechanism, i.e. the investigated reaction takes place via the formation of an intermediate complex. Moreover, these values refer to the rigidity and stability of the intermediate complex. Thus, the ring opening of the intermediate complex would be the rate controlling step.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.181-186
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• 2011

In this study, we used 3-(trimethoxysilyl)propylmethacrylate(MPS) silane coupling agent for surface modification of silica nanoparticles. We studied effects of reaction conditions such as solvent pH, MPS hydrolysis time, reaction time, and molar ratio of MPS to Si-OH groups on silica nanoparticle surfaces, on the surface modification reactions of silica nanoparticles. Fourier Transform Infrared Spectroscopy(FTIR), Elemental Analysis(EA) and solid state crosspolarization magic angle spinning(CP/MAS) Nuclear Magnetic Resonance Spectroscopy(NMR) techniques were used to determine the type and the degree of surface modification. We found MPS reacts preferentially with Si-OH groups of the silica nanoparticles as monomeric form at solvent pH = 4.5. But increasing hydrolysis time of MPS from 30 mins to 90 mins, and molar ratio of MPS to Si-OH groups on silica nanoparticle surfaces, we found that MPS reacts preferentially with Si-OH groups of the silica nanoparticles as oligomeric form.

• 월간산업보건
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• s.90
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• pp.2-8
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• 1995

원자 흡수 분광법과 용매 추출을 이용한 크롬의 정량분석 조건을 연구하였다. tertiary amine류 중 octy기를 갖는 trioctylamine(TOA)과 quaternary ammonium salt류 중 octy1 기를 갖는 trioctylmethylammonium chloride(TOMAC)가 음이온 교환기로 사용되었다. 또한 첨가되는 산의 종류와 산의 농도 변화에 따라서 원자흡수분광기를 이용하여 흡광도를 측정하였다. TOA사용시 염산의 농도가 0.1M-0.3M사이, TOMAC사용시 염산의 농도가 0.03M-0.1M사이에서 최대 흡광도를 나타내었다. 산이 첨가된 MIRK에 용해된 TOA나 TOMAC와 Cr과의 mole농도 비율이 1:1이상이 된 것이 최대 추출효율을 보았다. 추출과정을 검토한 결과, 본 실험에서 사용된 방법은 비슷한 다른 방법들과 비교하여 보면 크롬의 추출효율이 좋은 것으로 판명되었다.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.350-351
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• 2000

알데히드는 여러 가지 악취물질중의 하나로서 공기 중에 미량으로 존재하면서 냄새를 일으키며, 건강 위해성도 큰 물질이다. 본 연구에서는 휘발성이 강하면서 건강에 유해하여 문제가 되고 있는 이러한 aldehyde 화합물을 간편하게 분석할 수 있는 방법을 개발하고저 하였다. 기존의 aldehyde 분석에서는 알데히드를 DNPH와 같은 유도체로서 변환시킨 뒤에 주로 HPLC로 분석하는 방법을 사용하였다. 이 방법은 보편적으로 많이 알려져 있으나 HPLC가 갖고 있는 단점(크로마토그파피의 낮은 분해능, 긴 분석시간, 다량의 고가 HPLC용매 소모)을 안고 사용해야 하는 불편한 점도 있다. (중략)

• Journal of the Korean Chemical Society
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• v.15 no.5
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• pp.219-222
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• 1971

The kinetics of the solvolysis of benzyl and p-or m-substituted benzyl bromides in various alcohols have been determined by an electric conductivity method. From these reactions, a curved Hammett plot is obtained and a mechanism is proposed to account for the nonlinear behavior observed. In addition, effects of solvent polarity on the activation parameters for the solvolysis of benzyl bromides are discussed.

• Analytical Science and Technology
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• v.18 no.5
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• pp.403-409
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• 2005

Polycyclic Aromatic Hydrocarbons(PAHs) contamination arises from several sources including processing of food(smoking, direct drying, cooking) and environmental contamination of air, water, or soil, the later being considered as the most important. In this study, to establish the analytical method for some PAHs[benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, indeno(1,2,3-c,d)pyrene] in fish, alkali digestion time, extraction solvents, elution volume of florisil cartridge for clean-up have been optimized. The methodology involved saponification and extraction with n-hexane, clean-up on Sep-Pak florisil cartridges and determination by HPLC/FLD(High Performance Liquid Chromatography/Fluorescence Detector). Overall method recoveries for 8 PAHs spiked into these products ranged from 90 to 106%.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.26-31
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• 1997

Bee venom (Apis mellifera) phospholipase $A_2$ solubilized in reversed micelles containing small amount of water stabilized by surfactant could catalyze the hydrolysis of dipalmitoyl phosphatidylcholine (DPPC). A sensitive and simple high performance liquid chromatographic (HPLC) methodology of phospholipase $A_2$ assay for the hydrolysis of DPPC was developed. Kinetic analysis of the phospholipase $A_2$-catalyzed reaction was found to be possible in reversed micelles. Among the surfactants and organic solvents tested, aerosol-OT and isooctane were most effective for the hydrolysis of DPPC in reversed micelles. Optimal temperature, optimal pH, $K_{m,app.},\;V_{max.,app.}$ and activation energy were determined to be $35{\sim}40^{\circ}C$, 7.0, 8.73 mM, 2.83 units/㎎ protein and 12.31 kcal/mole, respectively. The hydrolysis activity was dependent on water content and maximum activity was obtained at R value (=[water]/[aerosol-OT]) of 10.0.