• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.524-530
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• 2011

In the present study, we demonstrate that SRM LC-MS/MS method developed by Luo et al. (ref. 10) can be successfully applied to the quantitative analysis of intracellular metabolites in E. coli that are collected at the exponential and stationary growth phases. A focus is given on measuring the changes in the concentrations of intracellular metabolites in batch cultures, which were induced during both the dynamically changing exponential and stationary growth phases. The following intracellular metabolites are quantified in the exponential and stationary phases of E. coli growth, using the SRM mode of a triple quadrupole mass spectrometer: glucose-1-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate, pyruvate, acetyl-coenzyme A, 6-phosphogluconate, ribulose-5-phosphate, xylulose-5-phosphate, erythrose-4-phosphate. The determined intracellular metabolite concentration profiles are shown to be in a good agreement with the growth profiles of E. coli, which clearly indicates that SRM LC-MS/MS can be successfully used for following the metabolite changes induced at different growth stages.

• 상하수도학회지
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• 제30권6호
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• pp.691-698
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• 2016

This study was carried out to investigate the characterization of iron oxide nanotubes (INTs) by anodization method and applied adsorption isotherms and kinetic models for phosphate adsorption. SEM analysis was conducted to examine the INTs surface formation. Further XRD and XPS analysis were performed to observe the crystal structure of INTs before and after phosphate adsorption. AFM analysis was conducted to determine of Fe foil surface before and after anodization. Phosphate stock solution for adsorption experiment was prepared by $KH_2PO_4$. The batch experiment was conducted using 20 ml phosphate stock solution and $40cm^3$ of INTs in 50 ml conical tube. Adsorption isotherms were applied Langmuir and Freundlich models for adsorption equilibrium test of INTs. Pseudo first order and pseudo second order models were applied for interpretation of adsorption rate by reaction time. The determination coefficient ($R^2$) values of Langmuir and Freundlich models were 0.9157 and 0.8876 respectively.

• Journal of Biosystems Engineering
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• 제36권5호
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• pp.326-333
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• 2011

The need for rapid on-site monitoring of hydroponic macronutrients has led to the use of ion-selective electrodes, because of their advantages over spectrophotometric methods, including simple methodology, direct measurement of analyte, sensitivity over a wide concentration range, and low cost. Stability and repeatability of response can be a concern when using multiple ion-selective electrodes to measure concentrations in a series of samples because accuracy might be limited by drifts in electrode potential. A computer-based measurement system could improve accuracy and precision because of both consistent control of sample preparation and easy calibration of sensors. Our goal was to investigate the applicability of a cobalt-based electrode used in conjunction with a laboratory-made automated test stand for quantitative determination of ${PO_4}^-$ in hydroponic solution. Six hydroponic solutions were prepared by diluting highly concentrated paprika hydroponicsolution to provide a concentration range of 1 to 300 ppm $PO_4$-P. A calibration curve relating electrode response to phosphate in paprika hydroponic solution titrated to pH 4 with 0.025M KHP was developed based on the Nikolskii-Eisenman equation with a coefficient of determination ($R^2$) of 0.94. The laboratory-made test stand consisting of three cobalt-based electrodes measured phosphate concentrations similar to those obtained with standard laboratory methods (a regression slope of 0.98 with $R^2$ = 0.80). However, the y intercept was relatively high, 30 ppm, probably due to the relatively large amount of variation present among multiple measurements of the same sample. Further studies on the high variation in EMFs obtained with cobalt electrodes during replicate measurements were required for P estimations comparable to those obtained with standard laboratory instruments.

• 분석과학
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• 제8권3호
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• pp.273-279
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• 1995

납과 카드뮴을 포함하는 여러 가지 농도의 동결건조된 혈액이 외부정도관리 시료로서 제조되었다. 이 시료들은 흑연료 원자흡수분광법(GFAAS)을 이용하여 성능이 파악되었다. 매트릭스 개선제로서 0.1% ammonium dihydrogen phosphate와 0.1% Triton X-100을 사용하여 섭씨 600 내지 650도의 회화온도에서 혈액에 있는 납과 카드뮴의 정량 분석을 위한 GFAAS의 최적 분석조건이 얻어졌다. 제조된 혈액의 균질도와 안정도는 최적화된 분석조건에서 연구되었다.

• Preventive Nutrition and Food Science
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• 제7권1호
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• pp.12-17
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• 2002

Simultaneous determination of nine water-soluble vitamins contained in multi-nutrient tablets was carried out by reversed phase high-performance liquid chromatography (RP-HPLC) equipped with analytical $C_{18}$ column and UV (270 nm) detector. Those standard vitamins were successfully separated within 23 minutes by gradient elution with solvent A (0.5 M potassium phosphate monobasic) and solvent B (0.25 M potassium phosphate monobasic-methanol, 1:1). Calibration curves showed good linealities with correlation coefficients (> 0.92) in tested ranged respectively. The detection limits were considered to be 2.1 ng for ascorbic acids 60 ng for Vit B$_{6}$ 3 ng for p-aminobenzoic acid, 9 ng for niacinamide, 9 ng for thiamin, 5.0 ng for folic acid and 1.5 ng for riboflavin at 0.05 a.u.f.s. Solid phase extraction through Sep-Pak (C$_{18}$ ) cartridge was successfully applied for purification of water soluble vitamins in commercial multi-nutrient tablets.ts.

• Nuclear Engineering and Technology
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• 제16권3호
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• pp.131-135
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• 1984

Tri-n-butyl phosphate를 이용한 Sr-90의 정량법에 전처리 과정을 도입시킨 방법을 적용하여 한국인 93명의 척추골내 Sr-90의 함량을 측정하였다. 그 결과 Sr-90의 함량은 여자의 경우 2.29 pCi/g Ca로 나타났고, 남자의 경우 1.73 pCi/g Ca로 나타났으며 남녀 전체적으로 2.01 pCi/g Ca의 평균값을 나타내 외국의 경우보다 다소 높은 값을 나타내었다. 한편 쥐의 복강내에 Sr-90을 주입시켜 각 골조직내의 Sr-90함량을 측정한 결과 주입된 Sr-90은 골조직의 종류에 상관없이 골고루 분포되었으며 주입된 전체 Sr-90의 약 반이 1일 이내에 각 골조직에 침적되었으며 그 이후 점차적으로 제거되는 것을 관찰할 수 있었다.

• Journal of Electrochemical Science and Technology
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• 제8권4호
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• pp.307-313
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• 2017

In this paper we report an electrochemical sensor based on ZnO-functionalized graphene oxide nanocomposite (ZnO-GO) for the sensitive determination of the cabergoline. Cabergoline electrochemical behaviors were investigated by cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV). The modified electrode shows electrocatalytic activity toward cabergoline oxidation in phosphate buffer solution (PBS) (pH 7.0) with a reduction of the overpotential of about 180 mV and an increase in peak current. The DPV data showed that the obtained anodic peak currents were linearly dependent on the cabergoline concentrations in the range of $1.0-200.0{\mu}M$, with the detection limit of $0.45{\mu}M$. The prepared electrode was successfully applied for the determination of cabergoline in real samples.

• 상하수도학회지
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• 제37권6호
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• pp.375-382
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• 2023

The binary oxide adsorbent using Fe and Mn (Fe-Mn) has been prepared by precipitation method to enhance the removal of phosphate. Different amounts of chitosan, a natural organic polymer, were used during preparation of Fe-Mn as a stabilizer to protect an aggregation of Fe-Mn particles. The optimal amount of chitosan has been determined considering the separation of the Fe-Mn particles by gravity from solution and highest removal efficiency of phosphate (Fe-Mn10). The application of Fe-Mn10 increased removal efficiency at least 15% compared to bare Fe-Mn. According to the Langmuir isotherm model, the maximum uptake (q_m) and affinity coefficient (b) were calculated to be 184 and 240 mg/g, and 4.28 and 7.30 L/mg for Fe-Mn and Fe-Mn10, respectively, indicating 30% and 70% increase. The effect of pH showed that the removal efficiency of phosphate was decrease with increase of pH regardless of type of adsorbent. The enhanced removal efficiency for Fe-Mn10 was maintained in entire range of pH. In the kinetics, both adsorbents obtained 70% removal efficiency within 5 min and 90% removal efficiency was achieved at 1 h. Pseudo second order (PSO) kinetic model showed higher correlation of determination (R²), suggesting chemisorption was the primary phosphate adsorption for both Fe-Mn and Fe-Mn10.

• 분석과학
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• 제12권2호
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• pp.99-104
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• 1999

자외선검출법과 이온크로마토그래피를 이용하여 소금물 중에 함유하는 몇 가지 음이온의 분리정량에 대하여 검토하였다. 분리관은 음이온교환수지(Dionex, AS7)를 사용하였고 용리액으로서는 sodium chloride/sodium phosphate 완충용액을 사용하였다. 단계적용리법을 적용하므로서 최적분리가 가능하였으며 8가지 음이온(iodate, bromate, nitrite, bromide, nitrate, chromate, iodide와 thiocyanate)이 40분내에 분리되었다. 여러 가지 농도의 NaCl용액(0.0 M-1.0 M)속에 존재하는 음이온들의 거동을 살펴보았다. NaCl의 농도가 진할수록 bromate, nitrite, bromide와 nitrate의 피크의 모양이 점점 넓어졌으나 chromate, iodide와 thiocyanate는 1.0 M NaCl 용액의 농도까지 피크모양이 거의 변하지 않았다. 또한 여러 가지 농도의 NaCl용액에서 음이온들의 검량곡선은 좋은 직선성을 보여주었으며, $50{\mu}L$ 시료용액에서 검출한계는 $10-720{\mu}g/L$ 이었다. 바닷물중의 bromide, nitrate와 iodide의 측정에 이방법을 적용하였다.

• 분석과학
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• 제28권2호
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• pp.98-105
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• 2015

버얼리종 담배에서 추출물에서 얻은 peroxidase와 다중벽 탄소 나노튜브를 이용한 dopamine 정량 바이오센서를 만들었다. Peroxidase는 dopamine을 dopamine quinone으로 산화시키는 반응의 촉매 역할을 한다. 이 논문은 효소의 농도, pH와 같은 바이오센서의 감응에 영향을 주는 parameter를 조사하였다. 또한, 전극의 감도, 직선성의 범위, 전극의 안정성을 조사하였다. 본 실험에 사용한 dopamine의 정량 센서는 pH 6.50, 0.010 M 인산 완충용액, -0.15 V의 가해준 전압에서 가장 좋은 감응을 나타내었다. 전극의 검출한계(S/N ＝3)는 2.7×10⁻⁶ M이었으며, 5.0×10⁻² M dopamine을 이용하여 10회 반복 측정한 상대표준편차는 1.3%이었다.