• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.405-406
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• 2005

A theoretical investigation of the solid-phase mechanochemical synthesis of nano-sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3-mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact-friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano-TlCl by dilution of initial (2NaCl + $Tl_2SO_4$) mixture with the exchange reaction product (diluent, $zNa_2SO_4$, $z=z^*=11.25$) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano-TlCl obtained experimentally were compared with those for the model reaction KBr + TlCl + zKCl = (z + 1) KCl + TlBr ($z=z_l^*=13.5$), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2557-2560
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• 2010

To assay for antioxidant capacity of natural products considered important in producing human health benefits, a practical and economical method using pellet techniques was developed. A standard visualizing reagent, 1,1diphenyl-2-picryl-hydrazyl (DPPH), was mixed with a water-miscible polyvinyl alcohol (PVA), serving as a solid phase support for the DPPH reagent. A DPPH pellet was prepared by dropping a small volume of the DPPH solution onto PET film, and drying in an oven. The PVA-based DPPH pellet was dissolved into water, in which the water-miscible PVA plays as a non-ionic surfactant to help the DPPH reagent to be dissolved into the solvent. Using the DPPH assay, the antioxidant capacity of water-soluble extracts of black soybean, barley, green tea, and green gram was examined. Among the natural products tested, green tea showed the highest antioxidant capacity. This PVA-based DPPH antioxidant assay can be further applied in the natural food, raw plant material, and health product inspection field.

• 한국응용과학기술학회지
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• 제20권4호
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• pp.358-365
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• 2003

Zirconium nitride powders were synthesized at a relatively lower temperature using methane as a reducing agent in the nitridation of zircoia. $ZrO_2$ powder was prepared by a sol-gel technique. The resulting sol-gel was centrifuged, and the gel was washed with deionized water. Anhydrous ammonia was used as the nitrogen source and methane was used as the reducing agent. Conversion diagrams show the equilibrium solid phase as a function of reagent concentrations for a specific temperature and gas pressure for the reagent system $NH_3-ZrO_2-CH_4$. The reagent concentration ranges within which pure ZrN is formed increase with increasing reaction temperature. Low pressure with an excess of hydrogen decreases the reaction temperature at which pure ZrN is formed. Low pressure together with the introduction of excess hydrogen into the reaction system increases Zr and N conversion efficiency and retards C deposition.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1976-1980
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• 2010

A simple and reliable method has been developed to selectively separate and concentrate trace amounts of Fe(III) ions from water and food samples by using flame atomic absorption spectrometry. A new reagent, 5-hydroxy-4-ethyl-5,6-di-pyridin-2-yl-4,5-dihydro-2H-[1,2,4] triazine-3-thione, was synthesized and characterized by using FT-IR spectroscopy and elemental analysis. Effects of pH, concentration and volume of elution solution, sample flow rate, sample volume and interfering ions on the recovery of Fe(III) were investigated. The optimum pH was found to be 5. Eluent for quantitative elution was 10 mL of 2 M HCl. The preconcentration factor of the method, detection limit (3s/b, ${\mu}gL^{-1}$) and relative standard deviation values were found to be 25, 4.59 and 1%, respectively. In order to verify the accuracy of the method, two certified reference materials (TMDA 54.4 lake water and SRM 1568a rice flour) were analyzed. The results obtained were in good agreement with the certified values. The method was successfully applied to the determination of Fe(III) ions in water and food samples.

• Archives of Pharmacal Research
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• 제21권6호
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• pp.651-656
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• 1998

A sensitive high-performance liquid chromatographic (HPLC) method for the determination of aloesin in plasma was developed. After solid-phase extraction from plasma and derivatization of aloesin and compound AD-1, which was prepared from aloesin as a internal standard, with 9-anthroylnitrile in the presence of quinuclidine, the derivatives were separated on a Inertsil ODS-3 column using acetonitrile/methanol/water (3:1:6) as a mobile phase, and detected fluorimetrically at 460nm with excitation at 360nm. The detection limit of aloesin was 3.2ng/ml in plasma (S/N=3).

• Archives of Pharmacal Research
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• 제20권5호
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• pp.486-490
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• 1997

A stereospecific HPLC method has been developed for the resolution of the enantiomers of salbutamol in human urine. After solid-phase extraction and derivatization with (S)-(-)-${\alpha}$-methyl-benzyl isocyanate, the diastereomeric derivatives were resolved $(R_s=1.59)$ on $5{\mu}M$ octadecylsilan column using 47% methanol as a mobile phase with fluorescence detection. The detection limit of each enantiomer was 10 ng/ml (S/N=3).

• Archives of Pharmacal Research
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• 제21권2호
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• pp.217-222
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• 1998

A stereospecific HPLC method has been developed for the resolution of the enantiomers of salbutamol in human urine. After solid-phase extraction and derivatization with 2,3,4,6-tetra-O-acetyl-$\beta$-D-glucopyranosyl isothiocyanate, the diastereomeric derivatives were resolved (Rs=1.83) on $5{\mu}m$ octadecylsilan column using 35% acetonitrile in 0.05M ammonium acetate buffer (pH=6) as a mobile phase with electrochemical detection. The diastereomeric derivatives were formed within 30 min. The detection limit of each enantiomer was 20 ng/ml (S/N=3).

• Bulletin of the Korean Chemical Society
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• 제26권6호
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• pp.943-946
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• 2005

An effective spectrophotometric determination of palladium with 4-(2-pyridylazo)-resorcinol (PAR) using molten naphthalene as a diluent has been studied. A red complex of palladium with PAR is formed at 90 ${^{\circ}C}$. In the range of pH 9.0-11.0, the complex is quantitatively extracted into molten naphthalene. The organic phase is anhydrously dissolved in $CHCl_3$ to be determined spectrophotometrically at 520 nm against the reagent blank. Beer’s law is obeyed over the concentration range of 0.1-2 ${\mu}g{\cdot}mL^{-1}$. The molar absorptivity and Sandell’s sensitivity are 8.0 ${\times}\;10^5\;L{\cdot}mol^{-1}{\cdot}cm^{-}1\;and\;0.49\;{\mu}g{\cdot}cm^{-2}$ respectively. From the results of tolerance limits, it was found that there was no interferences were observed for most of the ions examined and those somewhat high interferences by Co(II), Fe(II) and Bi(III) could be effectively masked by EDTA.

• 대한화장품학회지
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• 제30권3호
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• pp.399-404
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• 2004

새로운 Gly-His-Lys (약자로 GHK)가 결합된 키토산을 $N^{\alpha}-Fmoc$ 아미노산과 BOP 커플링 시약을 사용한 고상법에 의해 제조하였다. 이를 위해 키토산 마이크로 비드를 W/O 에멀젼 상분리법으로 평균 입자크기 70 마이크로미터로 얻었다. GHK 펩타이드는 순차적으로 고상법에 의해 키토산 마이크로비드 위에 커플링 하였다. 아미노산 분석을 실시한 결과 Gly, His, kys의 비율이 1.02:1.13:0.96의 비율로 나타나 이론치와 거의 일치함을 확인할 수 있었다. GHK 펩타이드가 결합된 마이크로비드의 세포증식 효과는 MTT 분석으로 측정하였다. 측정결과 GHK 펩타이드가 결합된 키토산 마이크로비드는 대조군인 펩타이드가 결합되지 않은 키토산 마이크로비드 자체에 비해 높은 세포증식 효과를 보였다.

• 분석과학
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• 제16권6호
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• pp.458-465
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• 2003

수용액 시료 중 휘발성 지방산을 HS (headspace)-SPME (Solid phase microextraction)를 이용하여 간편하고 빠르게 분석하는 방법에 대하여 연구하였다. 1-Pyrenyldiazomethane (PDAM)을 이용한 화이버 내 유도체화를 통하여 휘발성 지방산의 검출감도를 향상시킬 수 있었으며, SPME 추출조건으로 pH, 염 효과 및 초음파 추출에 대하여 조사하였다. 본 연구에서 개발된 방법을 기반으로 실제 폐수 중 휘발성 지방산을 추출하여 기체크로마토그래피/질량분석기-선택이온검색법으로 정량 분석하였다.