• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2235-2241
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• 2010

A reverse-phase HPLC method with detection by mass spectrometry is described for the simultaneous determination of doxifluridine and its two active metabolites, 5-fluorouracil (5-FU) and 5-fluorouridine (5-FUrd), in beagle dog plasma. The optimal chromatographic separation was achieved on a Waters $Xterra^{(R)}$ $C_{18}$ column ($4.6{\times}250\;mm$ i.d., $5\;{\mu}m$ particle size) with a mobile phase of 0.1% formic acid in a mixture of 99% methanol and purified water (99:1, v/v). The developed method was validated in beagle dog plasma with a lowest limit of quantification of $0.05\;{\mu}g/mL$ for both doxifluridine and 5-FU, and $0.2\;{\mu}g/mL$ for 5-FUrd. Doxifluridine and its two metabolites were stable under the analysis conditions, and intra- and inter-day accuracies exceeded 92.87%, with a precision variability ${\leq}11.34%$ for each analyte. Additionally, the method for quantifying doxifluridine and its two metabolites, 5-FU and 5-FUrd, in beagle dog plasma was applied successfully to the analysis of pharmacokinetic samples.

• YAKHAK HOEJI
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• v.37 no.1
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• pp.1-8
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• 1993

A procedure for the high-performance liquid chromatographic determination of Nebramycin factors in fermentation broth of Streptoalloteichus hindustanus ATCC 31218 mutant was investigated using pre-column derivatization and LTV detection. The method is based on pre-column derivatization of Nebramycin factors with 2,4-dinitrofluorobenzene(DNFB) in the presence of Tris (hydroxymethyl)aminoethane. The chromatographic separation of derivatives of Nebramycin factors and unknown impurities is achieved using reversed-phase column (NOVA-PAK $C_{18}$, Waters Co.) and AcCN : H$_{2}$O : AcOH (53.0:46.5:0.5) as a mobile phase. The mixture of these derivatives were separated within 35 minutes and the optimum wavelength($\lambda_{max}$ ) of the UV detector was 353 nm. The linearity of response for derivatives of Nebramycin factors is demonstrated for concentrations up to 500 $\mu\textrm{g}$/ml and the relative standard deviation is less than 0.79%. Detection limit was 1.67 ng for the 10 $\mu\textrm{l}$ sample volume employed.

• Analytical Science and Technology
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• v.34 no.5
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• pp.202-211
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• 2021

Volatile organic compounds (VOCs) in hazardous air pollutants (HAPs) have been regulated by the Air Pollution Control Act (1978) and their atmospheric concentrations have been monitored in 39 monitor sites in Korea. However, measurement standards of volatile organic compounds (VOCs) in HAPs at ambient levels have not been established in Korea. Primary reference gas mixtures (measurement standards) at ambient levels are required for accurately monitoring atmospheric VOCs in HAPs and managing their emissions. In this study, primary reference gas mixtures (PRMs) at 5 nmol/mol were developed in order to establish primary national standards of VOCs in HAPs at ambient levels. Primary reference gas mixtures (PRMs) were prepared in pressurized aluminum cylinders with special internal surface treatment using gravimetric method. Analytical methods using gas chromatography-flame ionization detector (GC-FID) coupled with a cryogenic preconcentrator were also developed to verify the consistency of gravimetrically prepared HAP VOCs PRMs. Three different columns installed in the GC-FID were evaluated and compared for the retention times and separation of eighteen target components in a chromatogram. Results show that the HAP VOCs PRMs at 5 nmol/mol were consistent within a relative expanded uncertainty (k=2) of less than 3 % except acrylonitrile (less than 6 %) and the 18 VOCs were stable for 1 year within their associated uncertainties.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.559-563
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• 2012

An analytical method for the simultaneous determination of veterinary medicines (amprolium and decoquinate) in cattle and chicken's muscle by HPLC/UV-vis was established. Samples were extracted by a HLB (Hydrophilic-Liphophilic Balance) cartridge with acetonitrile and methanol. Prior to HPLC injection, a mixture solvent (Water:MeOH, 1:1) was utilized as a reconstitution solvent. Chromatographic separation was achieved with a C18 column ($250{\times}4.6mm$, $5{\mu}m$) using gradient elution with 20 mM HFBA and MeOH:ACN (1:1.8). The calibration curves from the spiked blank matrix showed good linearity (above $r^2$=0.997) in the concentration range of $0.13-12.0mg\;kg^{-1}$. The relative recovery (accuracy) and limit of quantitation (LOQ) were in the range of 78.5-107.1% and $0.13-0.42mg\;kg^{-1}$, respectively. The developed method can be used to determine under the MRL (Maximum Residue Limits) levels of veterinary medicines in animal tissues.

• Journal of Powder Materials
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• v.16 no.5
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• pp.351-357
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• 2009

A two-step recovery method was developed to produce copper powders from copper chloride waste solution as byproducts of MoO$_3$ leaching process. The first step consisted of replacing noble copper ions with external Fe$^{3+}$ ions which were formed by dissolving iron scraps in the copper chloride waste solution. The replaced copper ions were subsequently precipitated as copper powders. The second step was cementation of entire solution mixture to separate (pure) copper powders from aqueous solution of iron chloride. Cementation process variables of temperature, time, and added amount of iron scraps were optimized by using design of experiment method and individual effects on yield and efficiency of copper powder recovery were investigated. Copper powders thus obtained from cementation process were further characterized using various analytical tools such as XRD, SEM-EDS and laser diffraction and scattering methods.Cementation process necessitated further purification of recovered copper powders and centrifugal separation method was employed, which successfully yielded copper powders of more than 99% purity and average 1$\sim$2$\mu$m in size.

• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.538-545
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• 2001

The ratio of regioisomers in nitration of biphenyl derivatives containing electron-with-drawing group was examined. The ratio of isomers was determined efficiently by quantitative analysis of $^1$H NMR spectrum of product mixture based on $^1$H NMR spectrum of each isomer. Some isomers were isolated after chemical transformation, nitro to amine or carboxylic acid to its ethyl ester, because direct separation was very difficult. To improve the regiselectivity, representative several reaction conditions were tried and the NMR method was applied to determine regioselectivity in nitration of biphenyl derivatives. It was observed that the regioselectivity depend on not only reaction conditions but also position and kind of substituents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.2055-2061
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• 2013

Recently, an understanding of new sources of liquid hydrocarbons such as bio-ethanol is economically very important. Successful design of distillation columns in a separation process depend on the availability of accurate vapor-liquid equilibrium data. For the binary system of Ethanol/3-methyl-l-butanol mixture, isothermal Vapor-liquid equilibrium data were measured at temperature of 50, 55, 60, 65, 70, 75 and $80^{\circ}C$. An empirical relation to predict Vapor-liquid equilibrium data was obtained from the above measured data. The predicted values are compared with the measured ones to be in a good agreement within accuracy of ${\pm}0.0005$, ${\pm}0.0022$.

• Plant Journal
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• v.13 no.3
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• pp.26-29
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• 2017

In this research, the composition of the feed stream is optimized in pressure swing distillation for separating of methanol-acetone. It is well known that the composition of feed stream in pressure swing distillation system has a great influence on the feasibility to separate mixture. The workscope of this study is to show better separation efficiency at specified pressure by controlling the composition of feed stream with recycle of two products. Based on the base case without recycle flow, two processes are designed that methanol and acetone are recycled to feed stream, respectively. Each processes are compared with total annual cost and as a result, the base case without recycle flow are most favorable.

• Elastomers and Composites
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• v.57 no.1
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• pp.13-19
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• 2022

Polycarbonate diol-based waterborne polyurethane (WPU) was prepared by prepolymer mixing process. The prepolymer mixture contained the polycarbonate diol, isophorone diisocyanate (IPDI), dimethylol propionic acid, triethylamine, and ethylenediamine (EDA). The NCO/OH ratio in the prepolymer was adjusted by controlling the molar ratio of IPDI, and its effects on the properties of WPU were studied. The structure of WPU was characterized by fourier transform infrared spectroscopy. The average particle size increased and viscosity decreased with increasing NCO/OH ratio and EDA content in WPU. The reduced phase separation between soft and hard segments increased glass transition temperature. The reduction in the thermal decomposition temperature could be attributed to the low bond energy of urethane and urea groups, which constituted the hard segment. Additionally, the polyurethane chain mobility was restricted, elongation decreased, and tensile strength increased. The hydrogen bond between the hard segments formed a dense structure that hindered water absorption.

• Composites Research
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• v.35 no.6
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• pp.402-411
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• 2022

In this study, the channels-contained hybrid membranes have been fabricated through the incorporation of glass fibers and GO sheets (GO/glass fibers, GG), or a mixture of chitosan/GO (CS/GO/glass fibers, CGG), as hybrid membranes using in organic dye removal. The material properties are well investigated the terms in the morphological, chemical, crystal, and thermal characterizations for verifying interactions in their formed structure. These hybrid membranes have been fitted well in pseudo-second order and Langmuir models that are associated with chemical adsorption and a monolayer approach, respectively. The highest adsorption ability of methylene blue and methyl orange reached 59.40 mg/g and 229.07 mg/g (GG); and 287.47 mg/g and 252.91 mg/g (CGG), which is more enhanced than that of previous GO-based other adsorbents. Moreover, the dye separation on these membranes could be favorable to superb sealing and trapping dye molecules from water instead of only the dye connection occurring on their surface, regarding the physically sieving effect. The membranes can also be reused within two and three adsorbing-desorbing cycles on the GG and CGG ones, respectively. These membranes can become future adsorbents to be applied for wastewater treatment due to their structural features.