• 분석과학
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• 제13권3호
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• pp.399-402
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• 2000

To determine the concentrations of microcystins present in lake water or in tap water using high performance liquid chromatography, it is necessary to concentrate a large volume of water samples (about 20 L) into very small volume (0.1-0.3 mL). Concentration can be conveniently done when disc type solid phase extraction (SPE) apparatus is used. Using this apparatus we have investigated the recovery rates of three kinds of microcystins, RR, YR, LR. The recovery rates were relatively low and the reproducibilities were not good either. It is expected, however, that the appropriate selection of the disc conditioning and eluting solvents and reproducible reconcentration process after SPE will improve both the recovery rates and the reproducibilities.

• 한국해양공학회지
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• 제27권4호
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• pp.9-13
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• 2013

The tensile properties of high manganese austenitic stainless steel with the two phase structures of deformation-induced martensite and reversed austenite were studied. Reversed austenite with an ultra-fine grain size of less than $0.3{\mu}m$ was obtained by reversion treatment. The two phases structures of deformation-induced martensite and reversed austenite were obtained by an annealing treatment in the range of $500^{\circ}C-700^{\circ}C$ for various times in 70% cold- rolled high-manganese austenitic stainless steel. The volume fraction of the reversed austenite increased rapidly with increases in the annealing temperature and time. In the stainless steel with the two phases of austenite and martensite, the strength decreased rapidly, while the elongation increased slowly and then rapidly increased with an increase in the volume fraction of the reversed austenite. Therefore, the strength and elongation were strongly controlled by the volume fraction of reversed austenite. A good combination of high strength and elongation could be obtained by the mixed structure of reversed austenite and deformation-induced martensite.

• 분석과학
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• 제10권6호
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• pp.408-417
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• 1997

기능성 헤테로 고리 화합물의 구조 이성질체를 정상 및 역상 액체 크로마토그래피를 이용하여 분리하고, 이들 분리를 위한 최적 조건을 알코올 변형체(modifier)를 포함한 삼성분 이동상(ternary solvent system)을 이용하여 조사했다. 삼성분 이동상의 경우 알코올 변형체가 컬럼의 활성 표면에 우선적으로 상호작용하여 비활성화(deactivation)시킴으로써 용질의 머무름을 감소시키고 꼬리 끌림(tailing)을 억제하여 분리선택성이 좋아지는 것으로 보인다. 구조 이성질체 분리의 경우 정상 액체 크로마토그래피를 이용할 경우가 분리 선택성이 더 좋은 것으로 나타났다. 또한, 헤테로 고리 화합물들의 머무름 거동은 역상 액체 크로마토그래피의 경우는 시료와 정지상과의 소수성 상호작용등으로 설명할 수 있었고, 정상 액체 크로마토그래피의 경우는 시료 분자와 충진제의 흡착표면과의 흡착력으로 설명할 수 있었다.

• 대한본초학회지
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• 제23권4호
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• pp.171-177
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• 2008

Objectives: This study presents a reversed-phase high-performance liquid chromatography- pulsed amperometric detection(RP-HPLC-PAD) method for the determination of puerarin and daidzin in Puerariae Radix extract and Chinese medicinal preparations. Methods: Chromatographic separation was performed using a 10% acetonitrile with a reversed-phase column(Unison UK-C18, $100mm{\times}2.0mm$ I.D.; $3{\mu}m$). The analyses were detected by pulsed amperometric detector(PAD) in alkaline conditions by combining with post-column NaOH solution. Geniposide was used as an internal standard. Results: The limit of detection(S/N=3) and the limit of quantification(S/N=10) were 0.025 ng, 0.075 ng for puerarin, and 0.05 ng, 0.15 ng for daidzin, respectively. The intra- and inter-day precisions(RSDs) were less than 6.5% and average recoveries of puerarin were 99.7-101.3% and those of daidzin were 101.0-102.8%. Conclusions: According to above results, we developed a determination method for puerarin and daidzin in Puerariae Radix with high sensitivity and selectivitely.

• 대한화학회지
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• 제38권7호
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• pp.502-508
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• 1994

염의 농도가 큰 시료용액중에 미량으로 함유되어 있는 U(VI)과 Th(VI)을 액상크로마토그래피로 동시에 분리, 정량하였다. 약 2ml의 시료를 pH5.5의 0.11M ${\alpha}$-HIBA 용리액과 함께 C_{18}$ 역상농축컬럼에 통과시켜 U(VI)과 Th(VI)을 농축시켰으며, 농축된 이들 원소들을 다시 비활성 C_{18}$ 역상분리컬럼에서 pH3.0의 0.17M ${\alpha}$-HIBA/0.0038 M 1-pentanesulfonate 용리액으로 각각 분리하였다. 분리된 이들 원소들은 Arsenazo III를 사용하는 postcolumn반응으로 검출되었으며, 검출한계는 두 원서 모두 1ppb이었다.

• KSBB Journal
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• 제16권3호
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• pp.241-245
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• 2001

Mass transfer rates have been measured for the extraction of enzyme from aqueous solution into a reverse-micelle phase at $25^{\circ}C$. The 420 mL vessel was carefully designed to maintain a planar interface between the aqueous and solvent phases, so allowing precise measurement of interfacial area, has been investigated. Sodium di-2-ethylhexyl sulfosuccinate(AOT) was the surfactant used. Factors varied included: agitator speed, pH, ionic strength and surfactant concentration. Samples were taken from the solvent phase at 15min intervals, and the amount of enzyme extracted was measured by UV absorption at 280 nm. The observed Sherwood numbers for the aqueous phase $Sh_1$were correlated interms of the aqueous phase Reynolds number $Re_1$, and modified Schmidt number $Sc_1$. $Sh_1=0.664Re_1^{0.5}Sc_1^{0.33}$

• Natural Product Sciences
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• 제10권6호
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• pp.262-267
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• 2004

A reversed-phase liquid chromatographic method for decursin and decursinol angelate of Angelicae gigantis Radix, an important crude drug in Korean traditional medicine, was developed and validated. Decursin and decursinol angelate, the structure isomer (pyranocoumarin) each other, are the main organic constituents in Angelicae gigantis Radix. This method was developed using a RP-18 column, UV detector at 280 nm and 50% acetonitrile solution containing 0.01 M sodium dodecyl sulfate and 25 mM sodium dihydrogen phosphate (pH 5.0) as the mobile phase. Various validation parameters were included and evaluated satisfactorily. Linearity was established in range 2-75 mg/ml of decursin and decursinol angelate (correlation coefficient = 0.9997 and 0.9995, respectively). This analytical method showed good accuracy (98.1% and 99.5%, respectively). Precision (repeatability) revealed a relative standard deviation value of 1.71% (decursin) and 3.19% (decursinol angelate). For intermediate precision measure the considered variables were equipment and days. A robustness test showing the influence of deferent counter-ion concentration in mobile phase was also performed.

• Archives of Pharmacal Research
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• 제23권6호
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• pp.568-573
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• 2000

A reversed-phase high-performance liquid chromatographic method was developed to determine the optical purity of bevantolol enantiomers. (S)-(-)-Menthyl chloroformate((-)-MCF), (S)-(-)-$\alpha$-methylbenzyl isocyanate((-)-MBIC) and 2,3,4,6-tetra-O-acetyl-$\beta$-D-glucopyranosyl isothiocyanate(GITC), which can react with the secondary amine group of bevantolol were investigated as chiral derivatization reagents. Among them indirect chiral HPLC method using CITC gave the best result. The derivatization proceeded quantitatively within 20 min at room temperature. Separation of the enantiomers as diastereomers was achieved by reversed-phase HPLC within 20min using ODS column. Different ratios of (S)-(-)-bevantolol and (R)-(+)-bevantolol were prepared. Enantiomeric separation of these mixtures took place on a chiralcel OD column or, after derivatization with GITC, on a ODS column. No racemization was found during the experiment. This method allowed determination of 0.05% of either enantiomer in the presence of its stereoisomer and method validation showed adequete linearity over the required range.

• Natural Product Sciences
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• 제26권3호
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• pp.236-243
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• 2020

Salvia plebeia R. Br. is a plant which has been used as an edible crop and traditional medicine in Asian countries. In this study, HPLC-PDA analysis and countercurrent chromatography (CCC) coupled with reversed-phase (RP) HPLC method were applied to isolate ten isolates from 3.3 g of n-butanol soluble extract from hot-water extract of S. plebeia. The use of CCC enabled us to efficiently fractionate the starting material with less sample loss and facilitate the isolation of compounds from S. plebeia extract using RP-HPLC. The isolates were determined to be caffeic acid (1), 6-hydroxyluteolin 7-O-β-D-glucoside (2), eudebeiolide B (3), (R)-rosmarinic acid (4), homoplantaginin (5), eudebeiolide D (6), plebeiolide C (7), salpleflavone (8), eupafolin (9) and hispidulin (10) based on the spectroscopic evidence.

• 분석과학
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• 제7권2호
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• pp.165-171
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• 1994

화학 발암제인 dimetylnitrosamine(DMN)을 Hamster에 구강투여하였을 때 간의 아미노산 조성에 미치는 영향을 규명하기 위하여 reversed phase liquid chromatography법으로 아미노산을 정량하였다. DMN을 투여한 실험군의 간에서의 아미노산의 농도는 대조군에 비해 aspartic acid, glycine, glutamine, histidine, proline, tyrosine, leucine 등은 약 2배, valine, tryptophan은 약 3배, phenylalanine은 약 10배 증가하였고, threonine은 23%로 감소하였으며, serine, alanine, arginine, methionine, isoleucine, lysine은 큰 변화가 없었다.