• Journal of Life Science
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• v.15 no.1 s.68
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• pp.136-140
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• 2005

Microbial cell-based UV spectrometric assay for the quantitative measurement of epoxide hydrolase activity was evaluated and optimized for the efficient screening of whole cell activity of novel epoxide hydrolase. Epoxide hydrolase activity was determined by measuring the increase of the oxidized product, benzaldehyde. The effects of the concentrations of phenyl-1,2-ethanediol, sodium metaperiodate and cells were optimized for epoxide hydrolase-catalyzed hydrolysis of styrene oxide. The relevant kinetic parameters of Km and $V_{max}$ for the hydrolysis of (R)-styrene oxide by Rhodotorula glutinis were determined from Lineweaver-Burk plot as 41.2 nmol/min$\cdot$mg dcw and 7.5 mM respectively, and coincided well with those from GC analysis.

• Clean Technology
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• v.12 no.3
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• pp.145-150
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• 2006

Electrolysis of aqueous solution produces hydroxide ions and proton ions for the hydrolysis of reactive organic compounds, and oxidizing agent such as hypochlorite ions for the oxidative decomposition of organic chemicals. Electrolytic decomposition of dying chemicals was tested with our custom made system, and analyzed by HPLC and UV-VIS spectrophotometer. The electrolytic system could decompose dying chemicals with very high reactivity and low cost. Disposal of byproduct and refill of reactant during electrolysis was not necessary. Decomposition time of dying chemicals is compared under similar conditions, and application to water purification is discussed.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.4
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• pp.207-217
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• 2011

In this study the complex formation reactions between uranium(VI) and 2,6-dihydroxybenzoate (DHB) as a model ligand of humic acid were investigated by using UV-Vis spectrophotometry and time-resolved laser-induced fluorescence spectroscopy (TRLFS). The analysis of the spectrophotometric data, i.e., absorbance changes at the characteristic charge-transfer bands of the U(VI)-DHB complex, indicates that both 1:1 and 1:2 (U(VI):DHB) complexes occur as a result of dual equilibria and their distribution varies in a pH-dependent manner. The stepwise stability constants determined (log $K_1$ and log $K_2$) are $12.4{\pm}0.1$ and $11.4{\pm}0.1$. Further, the TRLFS study shows that DHB plays a role as a fluorescence quencher of U(VI) species. The presence of both a dynamic and static quenching process was identified for all U(VI) species examined, i.e., ${UO_2}^{2+}$, $(UO_2)_2{(OH)_2}^{2+}$, and $(UO_2)_3{(OH)_5}^+$. The fluorescence intensity and lifetimes of each species were measured from the time-resolved spectra at various ligand concentrations, and then analyzed based on Stern-Volmer equations. The static quenching constants (log $K_s$) obtained are $4.2{\pm}0.1$, $4.3{\pm}0.1$, and $4.34{\pm}0.08$ for ${UO_2}^{2+}$, $(UO_2)_2{(OH)_2}^{2+}$, and $(UO_2)_3{(OH)_5}^+$, respectively. The results of Stern-Volmer analysis suggest that both mono- and bi-dentate U(VI)-DHB complexes serve as groundstate complexes inducing static quenching.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.376-376
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• 2023

전 세계적으로 중요한 담수 자원인 지하수의 미세플라스틱 오염에 대한 우려가 커지고 있다. 지하수 환경에서 미세플라스틱의 오염을 예측하고 평가하기 위해 대수층 내 현장 실태조사가 수행 중에 있으며, 실험실 규모의 컬럼 실험을 통해 지하수에서 미세플라스틱 이동 메커니즘을 조사하는 연구들이 수행되고 있다. 이러한 연구들은 많은 개수의 분석 시료를 동반하며, 환경 중 미세플라스틱 정량분석을 위해서 고가의 분석기기(라만분광기, 푸리에 변환 적외선(FTIR) 분광기, 열분해 가스크로마토그래피 질량분석기)를 사용하여 플라스틱의 종류를 판별하고 개수를 측정하고 있다. 또한, 컬럼 실험을 수행한 대부분의 선행 연구에서는 미세플라스틱 정량분석을 위해 탁도 분석, 분광광도계를 이용한 흡광도 분석, 현미경을 이용한 계수 방법 등을 이용하여 고가의 분석기기를 사용하지 않고 연구를 수행하였다. 하지만, 이러한 방법들은 유체 속 다른 물질이 포함되어있을 경우에 민감하고 농도를 비율 혹은 개수로 표현하기 때문에 질량 측면에서 미세플라스틱의 농도를 과소·과대 평가할 수 있다. 특히, 현미경을 이용한 계수 방법의 경우에는 분석에 많은 시간이 소요된다는 단점이 있다. 위에 언급한 다양한 분석법들의 단점들을 보완하기 위하여, 본 연구에서는 대수층 내 미세플라스틱 이동 특성을 규명하기 위한 실내 실험에 사용될 수 있는 형광이미지 기반의 미세플라스틱 정량분석법을 개발하였다. Nile Red 형광염료를 이용하여 미세플라스틱을 염색하고 사진을 촬영하여 미세플라스틱 시료의 질량과 미세플라스틱 형광이미지의 형광강도 간 상관관계를 분석하였다. 또한, Nile Red로 염색된 미세플라스틱 입자의 수중 노출 테스트를 진행하여, 실내 대수층 모의실험 시 미세플라스틱 질량을 정량화할 수 있는 적용 가능성을 평가하였다. 상관 분석 결과, 미세플라스틱 질량과 이미지의 형광강도는 높은 상관관계를 보였으며, 수중 노출 실험 전과 후의 미세플라스틱 입자의 형광강도 차이는 미미한 것으로 나타났다. 이러한 연구결과를 통해 본 연구에서 개발된 미세플라스틱 정량분석 방법이 포화 다공성 매체로 구성된 컬럼실험 시 유출수의 미세플라스틱 질량 추정에 유용하게 사용될 것으로 생각되며, 대수층 내 미세플라스틱의 이동 특성 규명 연구에 많은 도움이 될 것으로 기대된다.

• Journal of Applied Biological Chemistry
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• v.59 no.4
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• pp.361-364
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• 2016

We developed a spectrophotometric assay method for polyethoxylated ascorbic acidusing 3-ethyl ascorbic acid as standard material. The analytical method was validated by linearity, accuracy, precision, and stability. The coefficient of variation of the precision of the assay was less than 3.4 %. The linearity of the calibration curves in the desired concentration range is good ($r^2$>0.998). 3-Ethyl ascorbic acid and polyethoxylated ascorbic acid were stable in stock solution at room temperature for up to at least 6 h. The developed assay could be used for the content analysis of polyethoxylated ascorbic acid in samples.

• Korean Journal of Materials Research
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• v.7 no.7
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• pp.597-603
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• 1997

파장분산 분광분석기(Wavelength Dispersive Spectroscopy, WDS)는 다른 분석 방법에 비해 분해능이 좋고 측정 시간이 적게 걸리며, 또한 비용면에서 경제적이고 정량값이 실제값과 다르게 측정될 수 있다. 즉, 다성분계 박막에 있엇 X-선 발생 깊이가 작은 원소의 경우 X-선 발생 깊이가 큰 원소에 비해 조성값이 과장되어 측정된다. PZT박막의 경우에도 WDS로 측정한 조성은 박막의 두께에 따른 정확한 보정이 필요하다. 본 연구에서는 WDS를 이용하여 PZT박막의 조성을 측정할 때, 얇은 박막의 경우에도 조성을 정확하게 알아낼 수 있도록 박막의 두께에 따른 조성의 보정법을 제시하였다. 또한, 박막의 두께를 직접 측정하는 과정없이 WDS분석 결과로 얻는 각 원소들의 [ZAF]k 의 합으로부터 박막의 두께를 이론적으로 구하였으며, 이를 실험값과 비교하였다.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.540-547
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• 2007

Humic substances(HS) from Han River water was physic-chemically isolated by fractionational methods to investigate the seasonal distribution and to characterize the properties compared with intrinsic humic materials. Various HS samples were analyzed by element, Fourier transform infrared(FT-IR), proton nuclear magnetic resonance$(^1H-NMR)$ and fluorescence analyzers. The portion of HS from Han River water(HRHS) was 47.0% on the average, however it appeared that rainfall event brought about higher fraction of HS in Han River water by the periodic investigation. Aromaticity and humification degree of the HRHS were relatively lower than those of intrinsic humic materials originated from decomposing vegetation. FT-IR, $^1H-NMR$ and fluorescence spectroscopy showed the distinct differences between HRHS and intrinsic humic materials. Commercial humic materials could not represent structural and functional characteristics of local HS. The fluorescence spectroscopy, a relatively simple measurement, was found most useful tool to estimate humification degree for humic materials from particular sources.

• Clean Technology
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• v.23 no.1
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• pp.95-103
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• 2017

In this study, $ATiO_3$ (A = Ca, Sr, Ba) perovskite, which is the widely known for non $TiO_2$ photocatalysts, were synthesized using sol-gel method. And Ni was added at the A site of $ATiO_3$ by using that it is easy to incorporate. The physicochemical characteristics of the obtained $ATiO_3$ and Ni-$ATiO_3$ particles were confirmed using the X-ray diffraction (XRD) UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), the $N_2$ adsorption-desorption isotherm measurement, and X-ray photoelectron spectroscopy (XPS). The $H_2$ was produced using the photolysis of MeOH. Using the Ni-$ATiO_3$ photocatalysts, $H_2$ production was higher than using the $ATiO_3$ photocatalysts. Especially, $273.84mmolg^{-1}$ $H_2$ was produced after 24 h reaction over the Ni-$SrTiO_3$. Also in the water (0.1 M KOH) with the Ni-$SrTiO_3$, $H_2$ production was $961.51mmolg^{-1}$ after 24 h reaction.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.292-298
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• 1998

${\alpha}-Fe_2O_3$films were prepared by a dip-coating method using the mixed solution of ferric nitrate, ethylene glycol and acethyl acetone. The polymerization effect of the mixed solution was studied by FT-IR spectroscopic analysis, and the decomposition of organic parts and crystallization of the dip-coated film were investigated by FT-IR, XRD and DSC. In addition, AFM and SEM were employed to analyze the surface roughness and the thickness of ${\alpha}-Fe_2O_3$films.

• Journal of Life Science
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• v.17 no.2 s.82
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• pp.266-271
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• 2007

Bisphenol A (BPA) has been widely used as a monomer for production of epoxy resins and polycarbonate plastics. The annual production of BPA exceeds 640,000 metric tons in worldwide. BPA, a suspected phenolic endocrine disrupter, is moderately soluble and frequently detected in industrial wastewater. To date, HPLC and GC has been used for BPA analysis. However, HPLC and GC-analysis need high operation lost, experts, and an elaborate pre-treatment of samples, and is difficult to apply on-time and mass analysis. Therefore, simple, mass and rapid detection of BPA in environments is necessary. In the present study, spectrophotometric method of BPA quantification was developed. Based on blue-color product formation with BPA and ferric chloride/ferricyanide under the optimized conditions, the standard curve was acquired $({\lambda}_{750}=0.061\;BPA\;[{\mu}M]+0.07155,\;R^2=0.992)$. Using an established method, the BPA contents in the soil extract, and different water samples and living products, including disposable syringe, cup and plastic tube, were analyzed. The results suggested that the method is useful for BPA determination from different massive samples. Since the BPA metabolites, nontoxic 4-hydroxyacetophenone or 4-hydroxybenzaldehyde, did not form blue-color product, this method is also useful to screen a microorganism for BPA bioremediation.