• 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.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.100-100
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• 2022

Hovenia dulcis is a herbal plant, which belongs to the Rhamnaceae family and is a native of Japan, China and Korea. Its fruit stalk is called 'Jiguja' in Korea. It has been traditionally used as a medicinal plant in East Asia. It was reported to have detoxification effects on alcohol poisoning, and antioxidant, antidiabetic etc. Sample of 5 g was extracted with 50 mL of 70% EtOH. The supernatant was filtered by 0.45 ㎛ membrane filter before analysis. The UPLC system was performed on Waters alliance UPLC HSS T3 column (2.1 × 100 mm, 1.7 ㎛) with a UV detector. The gradient system was a binary eluent of 0.1% formic acid in water(A) and 0.1% formic acid in acetonitrile(B) with gradient conditions as follows: Initial, 10% B; 1 min, 10% B; 4 min, 20% B; 10 min, 25% B; 12 min, 30% B; 14 min, 90% B; 17 min, 90% B; flow rate of 0.2 mL/min. The samples were injected by 2 µL and were detected at UV 355 nm. As a result of analysis, chromatographic patterns appeared in two cases: samples analyzed for ampelopsin and myricetin, and samples analyzed for taxifolin and quercetin. Among the four compounds, the largest regional difference was found to be taxifolin.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.7
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• pp.486-493
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• 2003

Schottky type A $l_{0.33}$G $a_{0.67}$N ultraviolet photodetectors were fabricated on the MOCVD grown AlGaN/ $n^{＋}$-GaN and AlGaN/AlGaN interlayer/ $n^{＋}$-GaN structures. The grown layers have the carrier concentrations of -$10^{18}$, and the mobilities were 236 and 269 $\textrm{cm}^2$/V.s, respectively. After mesa etching by ICP etching system, the Si3N4 layer was deposited for passivation between the contacts and Ti/AL/Ni/Au and Pt were deposited for ohmic and Schottky contact, respectively. The fabricated Pt/A $l_{0.33}$G $a_{0.67}$N Schottky diode revealed a leakage current of 1 nA for samples with interlayer and 0.1$\mu\textrm{A}$ for samples without interlayer at a reverse bias of -5 V. In optical measurement, the Pt/A $l_{0.33}$G $a_{0.67}$N diode with interlayer showed a cut-off wavelength of 300 nm, a prominent responsivity of 0.15 A/W at 280 nm and a UV-visible extinction ratio of 1.5x$10^4./TEX>.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.209.1-209.1
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• 2012

TUS(Tracking Ultraviolet Setup)는 5x1019 eV 이상의 초고에너지 우주선의 스펙트럼과 그 기원, 그리고 고층대기 극한방전 현상(TLE) 관측을 위한 우주망원경이다. 위성 Lomonosov의 탑재체로 2013년에 발사예정에 있으며 지구로부터 550km 상공에서 지구를 돌며 3년 이상 임무를 수행할 예정이다. TUS는 크게 반사경과 Detector Module 두 부분으로 나뉜다. 7개의 육각형 프레넬 거울을 이용한 $2m^2$ 크기의 반사경과 256개의 PMT(Photo Multiplier Tube)로 구성된 Detector Module을 이용하여 지구 대기에서 초고에너지 우주선에 의해 발생하는 UV fluorescence와 Cherenkov light를 관측한다. TUS Detector Module의 한 부분인 Pinhole Camera는 본 연구단의 기술로 직접 개발한 탑재체로서 TUS 반사경을 통하지 않고 두개의 $8{\times}8$ 어레이 MAPMT (Multi Anode PMT)가 직접 지구를 바라보며 고층대기 극한방전 현상을 관측한다. Pinhole camera는 TUS의 시야각을 포괄하는 넓은 시야각을 가지고 있으며 빠른 트리거 시스템으로 고층대기 극한 방전 현상을 관측하며, 이 방전현상과 TUS가 관측하는 초고에너지 우주선과의 상관 관계를 연구한다. 현재 TUS 및 Pinhole Camera는 러시아에서 조립되어 우주환경 인증 시험 및 인터페이스 테스트가 진행되고 있다. 본 발표에서는 TUS와 Pinhole Camera를 소개하고 현재까지의 진행상황 및 테스트 결과에 대해 보고하고자 한다.

• The Korea Journal of Herbology
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• v.27 no.6
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• pp.43-48
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• 2012

Objectives : This study was investigated to determine the contents of pesticide residues and sulfur dioxide residues in commercial herbal medicines in Korea. Methods : Chromatographic test was performed on 100 samples consisted with 10 kinds of medicinal plants including improted and domestic products. To establish 19 pesticide residues (DDE, DDD, DDT, Dieldrin, Methoxychlor, BHC isomers, Aldrin, Endosulfan isomers, Endrin, Captan, Procymidone, Chlorpyrifos and Imidacloprid) in commercial herbal medicines, chromatographic equipments were used with the gas chromatography-mass detector and gas chromatography-electron capture detector for qualitative analysis. The imidacloprid analysis was performed by high performance liquid chromatograpgy-ultraviolet detector at 270 nm UV wavelength. The contents of sulfur dioxides were analyzed by modified Monnier-Williams method. All methods were based on notification procedure of Korea Food & Drug Administration (KFDA). Results : The residual pesticides were not founded in improted and domestic samples. Among 100 samples, the residues of sulfur dioxide in 73 samples were not detected and 25 samples showed contents in the range of 0~21.90 mg/kg. The excess samples of MRLs were 2 samples (30 mg/kg to medicinal herbs), Asiasari Radix et Rhizoma (Imported product) and the average amount of sulfur dioxide in 2 unsuitable samples were 14.83 mg/kg. These samples were found to transgress KFDA regulatory guidance of residual sulfur dioxide. Conclusion : These results are able to use as basic data to improve the reliability and value of commercial medicinal herbs.

• Korean Chemical Engineering Research
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• v.45 no.5
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• pp.460-465
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• 2007

Endosulfan-${\alpha}$ endosulfan-${\beta}$ and endosulfan-sulfate, which are classified as pesticides, were degraded by use of UV energy and ultrasonic irradiation. The degradation residuals were analysed by gas chromatography with an electron capture detector and TOC (total oragnic carbon) analysis. The reactions were conducted in a quartz annular reactor equipped with a low pressure mercury multilamp (8Wx2) and a sonic generator. All the aqueous solutions were concentrated as 10 mg/L initially. Endosulfans were degraded each to result in 48.2% (${\alpha}$), 50.0% (${\beta}$) and 76.5% (sulfate) of removal efficiency by UV energy, and 66.9% (${\alpha}$), 55.8% (${\beta}$) and 72.7% (sulfate) by ultrasonic irradiation, respectively. In contrast to the results of the single-component solutions, degradation of the endosulfan-sulfate was greatly suppressed to result in the lowest degradation rate and removal efficiency in the three-component solutions. This finding suggests that there should be a reversible reaction with a substantially low equilibrium constant between endosulfan-${\alpha}$ or -${\beta}$ and -sulfate in the coexistence of the three endosulfans. TOC data showed the endosulfans were decomposed by 20%~40% toward complete mineralization, producing a quantity of intermediates induced by the radical reactions. We found that all the decay reactions considered in this study nicely fell into pseudo first-order rate.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.46-54
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• 1989

The extraction method and quantitative analysis for the fat-soluble vitamins present in food stuffs and vitamin products have been investigated. The simultaneous separation and analysis of the vitamins by reverse phase high performance liquid chromatographic method was conducted using an isocratic elution with methanol : water (95 : 5) eluent on a Novapak $C_{18}$ column. The detection of vitamins was achieved by a variable wavelength UV detector. To improve the detection sensitivity detection wavelengths were set at the highest absorption bands such as 330, 265, 285, and 290nm for the respective vitamins. The analysis for the fat-soluble vitamins was finished within 40 minutes. Alkaline hydrolysis and enzymatic hydrolysis were investigated for the sample preparation; and liquid-liquid extraction and liquid-solid extraction were attempted for the extraction of vitamins. Both hydrolysis methods were turned out to be appropriate for the analysis for vitamins A, D, and E, while for the analysis of vitamin K the enzymatic hydrolysis method demonstrated better results. Diethyl ether, pentane, and n-hexane were found to give higher recovery for the liquid-liquid extraction and silica cartridge for the liquid-solid extraction.

• Journal of Food Hygiene and Safety
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• v.32 no.5
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• pp.434-442
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• 2017

The UV light in sunlight breaks down the chemical bonds in a polyolefin polymer through a process called photodegradation, ultimately causing cracking, chalking, colour changes, and loss of physical properties such as impact strength, tensile strength, elongation, and others. UV absorbers are used to prevent or terminate the oxidation of plastics by UV light. They are receptive to UV radiation and dissipate the energy harmlessly as heat. Benzotriazoles and benzophenones are used mainly in polyolefins such as polyethylene and polypropylene. In this study, we have developed a method for the analysis of 12 UV absorbers, which are Uvinul 3000, Cyasorb UV 24, Uvinul 3040, Tinuvin 312 and P, Seesorb 202, Chimassorb 81, Tinuvin 329, 234, 326, 328 and 327, migrated from the food packaging materials into four food simulants for aqueous, acidic, alcoholic and fatty foods. The UV absorbers in food simulants were determined by reversed-phase high performance liquid chromatograph-ultraviolet detector with 310 nm after solid-phase extraction with a hydrophilic-lipophilic balance (HLB) cartridge or dilution with isopropanol. The analytical method showed a good linearity of coefficient ($R^2{\geq}0.99$), limits of detection (0.049~0.370 mg/L), and limits of quantification (0.149~1.120 mg/L). The recoveries of UV absorbers spiked to four food simulants ranged from 70.05% to 110.13%. The developed method would be used as a reliable tool to determine concentrations of the migrated UV absorbers.

• Korean Journal of Food Science and Technology
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• v.39 no.2
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• pp.114-121
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• 2007

The purpose of this study was to investigate 253 kinds of pesticide residues in 58 commercial dried agricultural products in Seoul. The determinations of the pesticide residues were performed using multiresidue methods and were carried out by a gas chromatography-nitrogen phosphorus detector (GC-NPD), an electron capture detector ($GC-{\mu}ECD$), a mass spectrometry detector (GC-MSD) and high performance liquid chromatography-ultraviolet detector (HPLC-UV), and a fluorescence detector (HPLC-FLD). The pesticide residue detection rate in the commercial dried agricultural products was 24.1% (14 of 58 samples). Twelve pesticide residues without maximum residue limits (MRLs) were detected. In the vegetable groups, the frequency of pesticide residues was found to be in the increasing order of dried fruiting vegetables > dried leafy vegetables > dried stalk and stem vegetables. The pesticides used on dried red pepper in the dried fruiting vegetables were varied (7 kinds) and numerous (4 of 8 samples). The pesticide types detected in the commercial dried agricultural products were in the order of pyrethroid > organochloride > organophosphorus and insecticide > fungicide > herbicide ${\cdot}$ nematicide. The primary pyrethroid pesticide detected was cypermethrin. According to the producing areas of products, large numbers of pesticide residues were found in the order of Korea, China, North Korea, USA, and Vietnam.

• Archives of Pharmacal Research
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• v.9 no.4
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• pp.211-214
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• 1986

A simultaneous determination method of alkaline earth metals was attempted with the conventional high performance liquid chromatographic system. Four cations, namely, magnesium, calcium, strontium and barium ion, were injected directly as aqueous solution into an eluent containing copper chloride solution and and were successfully separated and determined on a separating column (Zipax SCX, 4.6 mm i.d. ${\times}25$ cm length, Du Pont, USA) by using a variable wavelength UV detector. The linear calibration curves were obtianed in the range from $1.0{\times}10^{-4}M$ to $5.0{\times}10^{-4}M$ and the correlation coefficient of the calibration curve for each metal of magnesium and calcium in tap water. Alkaline earth metals were determined with the conventional high performance liquid chromatographic system.