• Title/Summary/Keyword: Electroanalytical method

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Putative multiple reaction monitoring strategy for the comparative pharmacokinetics of postoral administration Renshen-Yuanzhi compatibility through liquid chromatography-tandem mass spectrometry

  • Sun, Yufei;Feng, Guifang;Zheng, Yan;Liu, Shu;Zhang, Yan;Pi, Zifeng;Song, Fengrui;Liu, Zhiqiang
    • Journal of Ginseng Research
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    • v.44 no.1
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    • pp.105-114
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    • 2020
  • Background: Exploring the pharmacokinetic (PK) changes of various active components of single herbs and their combinations is necessary to elucidate the compatibility mechanism. However, the lack of chemical standards and low concentrations of multiple active ingredients in the biological matrix restrict PK studies. Methods: A putative multiple reaction monitoring strategy based on liquid chromatography coupled with mass spectrometry (LC-MS) was developed to extend the PK scopes of quantification without resorting to the use of chemical standards. First, the compounds studied, including components with available reference standard (ARS) and components lacking reference standard (LRS), were preclassified to several groups according to their chemical structures. Herb decoctions were then subjected to ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry analysis with appropriate collision energy (CE) in MS2 mode. Finally, multiple reaction monitoring transitions transformed from MS2 of ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry were used for ultrahigh-performance liquid chromatography coupled with triple quadrupole mass spectrometry to obtain the mass responses of LRS components. LRS components quantification was further performed by developing an assistive group-dependent semiquantitative method. Results: The developed method was exemplified by the comparative PK process of single herbs Radix Ginseng (RG), Radix Polygala (RP), and their combinations (RG-RP). Significant changes in PK parameters were observed before and after combination. Conclusion: Results indicated that Traditional Chinese Medicine combinations can produce synergistic effects and diminish possible toxic effects, thereby reflecting the advantages of compatibility. The proposed strategy can solve the quantitative problem of LRS and extend the scopes of PK studies.

Assembly of Gold Nanoparticles on Electrospun Polymer Nanofiber Film for SERS Applications

  • Wang, Li;Sun, Yujing;Wang, Jiku;Li, Zhuang
    • Bulletin of the Korean Chemical Society
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    • v.35 no.1
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    • pp.30-34
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    • 2014
  • We report a novel approach for fabricating active surface-enhanced Raman scattering (SERS) substrate for sensitive detection. This approach is based on the assembling of gold nanoparticles (AuNPs) onto the electrospun polycaprolactone (PCL) nanofiber film. The hydrophobic surface of PCL nanofiber film was pretreated using UV-inducing graft polymerization with acrylic acid. Afterwards this PCL nanofiber film was incubated with the AuNP solution to promote the assembly of AuNPs onto the PCL nanofibers and the formation of SERS active substrate. 4-aminothiophenol (4-ATP) molecule was used as a test probe for SERS experiments, indicating that the substrate has high sensitivity to SERS response. Our method has great advantage in term of environment-friendly synthesis, large-scale, high stability and good reproducibility. This highly active SERS substrate can be employed to detect the drug molecule, 2-thiouracil.

Electroanalytical Measurement of TEDA (Triethylenediamine) in the Masks of War

  • Ariani, Zahra;Honarmand, Ebrahim;Mostaanzadeh, Hossein;Motaghedifard, Mohammadhassan;Behpour, Mohsen
    • Journal of Electrochemical Science and Technology
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    • v.8 no.1
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    • pp.43-52
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    • 2017
  • In this paper, for the first time, the electroanalytical study of Triethylenediamine, TEDA was done on a typically graphene modified carbon paste electrode (Gr/CPE) in pH=10.5 of phosphate buffer solutions (PBS). The surface morphology of the bare and modified electrodes was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electro-oxidation of TEDA was investigated at the surface of modified electrode. The results revealed that the oxidation peak current of TEDA at the surface of Gr/CPE is 2.70 times than that shown at bare-CPE. A linear calibration plot was observed in the range of 1.0 to 202.0 ppm. In this way, the detection limit was found to be 0.18 ppm. The method was then successfully applied to determination of TEDA in aqueous samples obtained from two kinds of activated carbon from the masks of war. On the other hand, density functional theory (DFT) method at B3LYP/6-311++G** level of theory and a conductor-like Polarizable Continuum Model (CPCM) was used to calculate the $pK_a$ values of TEDA. The energies of lowest unoccupied molecular orbital ($E_{LUMO}$) and highest occupied molecular orbital ($E_{HOMO}$), gap energy (${\Delta}E$) and some thermodynamic parameters such as Gibbs free energy of TEDA and its conjugate acid ($HT^+$) were calculated. The results of calculated $pK_a$ were found to be in good agreement with the experimental values.

The Determination of TRC using an Electrochemical Method (I: Au electrode) (전기화학적 방법의 TRC(Total residual chlorine) 측정 연구(I: Au전극 이용))

  • Lee, JunCheol;Pak, DaeWon
    • Journal of Korean Society on Water Environment
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    • v.30 no.3
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    • pp.298-303
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    • 2014
  • We measured by electrochemical method for TRC (total residual chlorine) in ocean. From the results of Au electrode used for working electrode through cyclic voltammetry test, we obtained charge in voltage ranged from 0.0V-1.0V, and analyzed correlations of charge for TRC. Reduction peak TRC was investigated to be approximately 0.65 V vs. Ag/AgCl, and in the case that salt concentrations and temperatures in ocean appeared different, charge was analyzed for being different in the same TRC. However, in the case that each condition was constant, charge was measured at highly correlations for TRC.

Determination of Trace Strontium with o-Cresolphthaleoxon by Electroanalytical method (o-Cresolphthaleoxon을 이용한 스트론튬의 전기화학적 분석)

  • Choi, Won Hyung;Lee, Jin Sik;Kim, Do Hoon;Kim, Jae Soo
    • Analytical Science and Technology
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    • v.6 no.3
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    • pp.247-254
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    • 1993
  • Strontium can not be determined by conventional dc polarography method since it is very difficult to be reduced at the drop mercury electrode(DME) in aqueous solution. However the analytical sensitivity was improved by adsorptive stripping voltammetry in which electro-reduction of ligand in a complex formed between strontium and o-cresolphthaleoxone was performed. Strontium could be determined in range of $5{\sim}30{\mu}g/L$ concentration. This method was affected by coexistent alkali earth metal ions. Consequently ion exchange separation is recommended to analyze strontium in samples.

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The Determination of TRC using an Electrochemical Method (II: Pt electrode) (전기화학적 방법의 TRC(Total residual chlorine) 측정 연구(II: Pt전극 이용))

  • Lee, JunCheol;Pak, DaeWon
    • Journal of Korean Society on Water Environment
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    • v.30 no.3
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    • pp.304-310
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    • 2014
  • The conventional methods for total residual chlorine such as iodometry and DPD colorimetric can cause secondary pollution due to additional agents, also have a wide error range. As for alternative, electrochemical method can measure TRC(Total residual chlorine), and is not required as additional agents, also very suitable for using the fields of ballast water because test time is relatively fast. Therefore, this study was investigated for changing charge by agitation, salt concentration, and temperature change. Charge showed differences based on changes of reduction peak with or without agitation. In contrast, TRC and charge were well correlated in constant agitation speed. As TRC and charge were analyzed with high correlations in constant salinity and temperature of ocean, thereby conductivity was firstly measured, and charge had high correlation for TRC in spite of changing salinity and temperature Pt electrode revealed high reliability ($r^2=0.960$) because it was rarely effected by TRC, On the other hand, Au electrode appeared inadequate ($r^2=0.767$) to use sensor in less than 1.0 ppm of TRC. For high accuracy and detection of TRC, Pt and Au electrodes for test time were, respectively, 14 and 22 seconds. As a result, Pt electrode was more valuable than Au electrode in terms of response time.

Effectiveness of the Electrochemical Sensor for the Free Chlorine Measurement (잔류염소 측정용 전기화학센서의 유효성)

  • Kim, Hong-Won;Chung, Nam-Yong
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.5
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    • pp.720-725
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    • 2012
  • Sodium hypochlorite is used worldwide as a water disinfectant and in bleaching agent. Sodium hypochlorite applied to water initially undergoes hydrolysis to form free chlorine consisting of hypochlorous acid(HOCl) and hypochlorite ion($OCl^-$). For free chlorine determination, an electrochemical method is simple due to the electroactivity of free chlorine; it measures current and is free of most reagents. Amperometric free chlorine sensor has been developed with gold (Au)-based electrode. The 3-electrode free chlorine sensor whose working and counter electrodes were Pt exhibited excellent response to HClO at +400mV vs. Ag/AgCl/sat. KCl. In addition, the use of a pH error correction algorithm provided a reliable measurement of residual free chlorine in water sample without any pretreatment in the normal pH range(pH 6~8) of municipal water supply. The free chlorine sensor installed in on-line monitoring system could be used to continually monitor the level of residual free chlorine in real samples.

Binary Metal Oxide ($IrO_2-RuO_2$) pH Sensor Prepared by Sol-gel Method (Sol-gel 법을 이용한 이성분 금속산화물 ($IrO_2-RuO_2$) pH 센서)

  • Lee, Jeong-Ran;Oh, Se-Lim;Han, Won-Sik;Hong, Tae-Kee
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.2
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    • pp.190-196
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    • 2014
  • The sol-gel method was used to prepare binary metal oxide ($IrO_2-RuO_2$) pH sensor. The electrodes that mole percent compositions (mol%) of $IrO_2$ and RuO2 were 70:30 and 30:70 were selected. The characterizations of Nernstian response over pH range, response rate, interference on alkaline metals and reproducibility were investigated. Also the electroanalytical properties of these electrodes were evaluated in comparison with a commercial glass pH electrode. The composition of $IrO_2:RuO_2$ 70:30 mol% was chosen as better electrode formulation. The electrode was not susceptible to the action of interfering ions such as $Li^+$, $Na^+$ and $K^+$.