• Analytical Science and Technology
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• v.11 no.2
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• pp.92-95
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• 1998

K-SGICs(synthetic graphite intercalation compounds) were synthesized in a modified two-bulb pyrex tube. The pressure in the two-bulb tube was maintained at approximately $10^{-3}$ torr for the reaction of potassium and graphite. Deintercalation process of the K-SGlCs obtained by the modified method was heat-treated by keeping in liquid paraffin between $25^{\circ}C$ and $1400^{\circ}C$. The thermal stability and the temperature dependence of the K-SGICs were characterized using differential scanning calorimeter(DSC) analyzer. Enthalpy and entropy for K-SGIC formations were calculated by confirming the deintercalation and thermodynamic exothermic reactions depending on the various temperatures. The structure changes and thermal stability of K-SGICs during the deintercalation reaction of potassium ions and the interlayer spaces of the synthetic graphite were identified by X-ray diffraction(XRD).

• Analytical Science and Technology
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• v.33 no.1
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• pp.23-32
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• 2020

Methamphetamine (MA) is the most common and available drug of abuse in Korea and its primary metabolite is amphetamine (AP). Detection of AP derivatives, such as MA, AP, phentermine (PT), MDA, MDMA, and MDEA by the use of immunoassay screening is not reliable and accurate due to cross-reactivity and insufficient specificity/sensitivity. Therefore, the analytical process accepted by most urine drug-testing programs employs the two-step method with an initial screening test followed by a more specific confirmatory test if the specimen screens positive. In this study, a gas chromatography-mass spectrometric (GC-MS) method was developed and validated for confirmation of MA and AP in human urine. Urine sample (500 µL) was added with N-isopropylbenzylamine as internal standard and ethyl chloroformate as a derivatization reagent, and then extracted with 200 µL of ethyl acetate. Extracted samples were analysed with GC-MS in the SIM/ Scan mode, which were screened by Cobas c311 analyzer (Roche/Hitachi) to evaluate the efficiency as well as the compatibility of the GC-MS method. Qualitative method validation requirements for selectivity, limit of detection (LOD), precision, accuracy, and specificity/sensitivity were examined. These parameters were estimated on the basis of the most intense and characteristic ions in mass spectra of target compounds. Precision and accuracy were less than 5.2 % (RSD) and ±14.0 % (bias), respectively. The LODs were 3 ng/mL for MA and 1.5 ng/mL for AP. At the screening immunoassay had a sensitivity of 100% and a specificity of 95.1 % versus GC-MS for confirmatory testing. The applicability of the method was tested by the analysis of spiked urine and abusers' urine samples.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.1
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• pp.75-89
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• 2009

The purpose of this study was to identify $PM_{2.5}$ sources and to estimate their contributions to the border of Yongin-Suwon area, based on the analysis of the $PM_{2.5}$ mass concentration and the associated inorganic elements, ions and carbon components. The contribution of $PM_{2.5}$ sources were estimated by using a positive matrix factorization (PMF) model to identify air emission sources. For this study, $PM_{2.5}$ samples were collected from May, 2007 to April, 2008. The inorganic elements were analyzed by an ICP-AES. The ionic components in $PM_{2.5}$ were analyzed by an Ie. The carbon components were also analyzed by DRI/OGC analyzer. After performing PMF modeling, a total of 12 sources were identified and their contributions were quantitatively estimated. The contributions from each emission source were as follows: 11.3% from oil combustion source, 3.4% from bus/highway source, 5.8% from diesel vehicle source, 4.7% from gasoline vehicle source, 8.8% from biomass burning source, 15.1 % from secondary sulfate, 5.2% from secondary nitrate source, 13.4% from industrial related source, 4.1% from Cl-rich source, 19.6% from soil related source, 1.0% from aged sea salt, and 7.4% from coal combustion source, respectively. This study provides basic information on the major sources affecting air quality, and then it will help to effectively control $PM_{2.5}$ in this study area.

• Korean Chemical Engineering Research
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• v.47 no.4
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• pp.476-480
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• 2009

A polymer composite electrolyte of a blend of poly(methyl methacrylate)(PMMA) and poly(ethylene oxide) (PEO) as a host polymer, the ethylene carbonate as a solvent, and $LiClO_4$ as a salt was studied. The crystallinity of the polymer electrolytes was evaluated using differential scanning calorimeter(DSC). The ionic conductivity of the polymer electrolytes was measured by frequency response analyzer(FRA) method. The effect of PEO/PMMA blend ratios on the ionic conduction in these electrolytes was investigated. The electrolyte films showed a phase separation due to immiscibility of the PMMA with the PEO. The PMMA-rich phase and the PEO-rich phase were produced during a film casting. The ionic conductivity of blend electrolyte was dependent on the content of PMMA and showed the highest value at 20 wt.%. However, when PMMA content exceeds 20 wt.%, the ionic conductivity was decreased due to the slow ionic transport through the PMMA-rich phase.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.206-210
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• 2011

We fabricated rod-like poly(lactic acid)(PLA) specimens through applying various methods of equal-channel angular extrusion(ECAE) process and investigated the change of thermal and mechanical properties of specimens before and after each ECAE process. Combining three re-injection routes(A, BC, and C) and three pass counts(1, 2 and 4) allowed us to fabricate 7 different PLA specimens. Thermal properties of each specimen were measured by both differential scanning calorimeter and thermo-gravimetric analyzer. Shear strains of each specimen with respect to applied loads were measured by indentation hardness tester. Field emmision scanning electron microscopy was used to observe internal microstructure of cross-section of each specimen. The observed microstructures qualitatively supported the explanation of hardness test results. Among 7 specimens, PLA-P2A showed the biggest shear strain probably due to its dense microstructure.

• Journal of Hydrogen and New Energy
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• v.17 no.3
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• pp.301-308
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• 2006

The present work explores the effect of carbon-supported platinum catalyst on the HI decomposition using gas adsorption analyzer, thermogravimetry, X-ray diffractometry, scanning electron microscopy, and gas chromatography. For this purpose, three types of activated carbon (C), Pt/C-1 wt.%, and Pt/C-5 wt.% were prepared. The HI gas conversion is crucially influenced by the amount of Pt on the carbon support. The more the amount of Pt was, the higher results in the HI gas conversion. For three types of catalysts, HI conversion increased with increasing the decomposition temperature but with decreasing the space velocity. The increase of HI conversion with temperature was more pronounced in activated carbon than that in Pt/C. From EDX result, it was found that the activated carbon comprised higher amount of iodine than the Pt/C after the decomposition reaction. This implies that the HI conversion is closely related to the amount of Iodine.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.286-292
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• 2020

This study presents an angular-based measurement on three-dimensional paper-based analytical devices (3D-PADs) for quantitative detection of albumin without using an image analyzer. We demonstrate a simple quantitative and straightforward approach based on the angle of the discolored area as detection criteria. 3D-PADs are rapidly fabricated by the wax-printing and laminating process. The 3D-PADs are treated with citrate buffer and tetrabromophenol blue to react with albumin in a sample solution. Dropping sample solution into sample pad in the 3D-PAD, fluid flows toward the assay zone laterally and vertically by capillary action. We find that the change of angle of the discolored area correctly reflects the concentration of albumin and is reliable determinant for the measurement of the albumin concentration. It is the first demonstration of angular-based detection as a simple, inexpensive, and equipment-free approach for point-of-care diagnosis.

• Tribology and Lubricants
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• v.32 no.5
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• pp.141-146
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• 2016

The diketopyrrolopyrrole (DPP) pigment is a bicyclic 8-π-electron system containing two lactam units. Typical DPP derivative pigments have melting points of over 350°C and very low solubility in most solvents, and show absorption in the visible region with a molar extinction coefficient of 33,000 dm²mol⁻¹ and strong photoluminescence with maxima in the range 500–600 nm. X-ray structure analyses of DPP show that the whole molecule is almost in one plane. The phenyl rings are twisted out of the heterocyclic plane and the intermolecular hydrogen bonding between neighboring lactam NH and carbonyl units influences the structure of the DPP pigment in the solid state. In this study, mono-N-alkylation and mono-N-arylation were undertaken for Pigment Red 264 or Pigment Orange 73 with alkyl halide and aryl halide, respectively, in the presence of sodium tert-butoxide as a base catalyst to improve the solubility of DPP pigments and their application as CO₂ indicators. The synthetic yield was in the range 11–88%. The indicator dyes are highly soluble in organic solvents and shows pH-dependent absorption (λ_max 501 and 572 nm for the protonated and deprotonated forms, respectively) and emission (λ_max 524 and 605 nm for the protonated and deprotonated forms, respectively) spectra. The mono-N-alkylated and mono-N-arylated DPP pigment was identified by ¹H-NMR (¹H-Nuclear Magnetic Resonance Spectrometer), FT-IR (Fourier Transform Infrared Spectroscopy), and MS (Mass Spectrometry). According to the results of color and hue properties obtained by a color matching analyzer, the synthesized DPP pigment material can be used as a CO₂ indicator.

• The Korean Journal of Mycology
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• v.16 no.3
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• pp.162-174
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• 1988

To separate and quantitate antitumor protein-bound polysaccharides of Coriolus versicolor, the constituents were obtained from the submerged culture of the mycelia(C) and from the extract of the carpophores of the wild fungus(N). The polysaccharides were degraded by methanolysis. The neutral monosaccharides were separated and quantitated by HPLC using microbondapak carbohydrate analysis column, refractive index detection and water-acetonitrile acetic acid elution. The analyses of these constituents by HPLC showed that the natural constituent(N) consisted of glucose, xylose and mannose, the average amount being 96.44, 2.16 and 1.73%, respectively. The fermentation constituent(C) consisted of mannose, glucose, xylose and galactose, the average amount being 61.30, 14.00, 12.95, and 11.75%, respectively. The analyses of these constituents by an amino acid analyzer showed that both C and N contained 17 amino acids.

• Journal of the Korean Chemical Society
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• v.30 no.1
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• pp.126-134
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• 1986

7-Alkyl-2-aminophenazine-5,10-dioxides bearing butyl, hexyl and octyl group were synthesized by the reaction of 4-aminophenol with 6-alkylbenzofuroxans which had been obtained from aniline and n-alkyl alcohols. And 2-aminophenazine-5,10-dioxide was prepared by the reaction of 4-aminophenol with benzofuroxan. Infrared, nuclear magnetic resonance spectrophotometers, and elemental analyzer were employed to identify the products concerned with the synthetic processes. Surface tension of aqueous solutions of these phenazine derivatives was determined by surface tensiometer and it was found that the surface tension decreased with an increase of the number of carbon in the alkyl group. Antimicrobial activities were evaluated in terms of minimum inhibitory concentration by a dilution method. The butyl derivative showed the highest activity among these derivatives. It was observed that the antimicrobial activity of these alkyl substituted 2-aminophenazine-5,10-dioxides was stronger than that of 2-aminophenazine-5,10-dioxide.