• Tribology and Lubricants
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• v.35 no.3
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• pp.151-157
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• 2019

Insulated oil degradation produces charged by-products, such as acids and hydro-peroxides, which tend to reduce the insulating properties of the oil. In this study, UV-vis spectroscopy measurement technology is developed and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate its ability to monitor the degradation of electrical insulating paper. The degradation characteristics of the insulating paper are appropriately represented through various types of measurement methods, such as the Tan (delta) method, $CO_2$ gas production measurement, the titration method, and IR spectroscopy. The results are demonstrated to be well comparable to a change in the fluorescence emission ratio (FER), which is defined as the shift in fluorescence intensity in the measured wavelength range, and also to the chromatic ratio, which is defined as a color shift to longer wavelength ranges. The results also show that, by using UV-vis spectroscopy, it is possible to detect the degradation of the insulating paper. This study suggests that UV-vis spectroscopy can be applied as an alternative to high-performance liquid chromatography, which is the internationally recognized measurement technology for cellulose paper degradation. The FER detector is also verified to be useful as an effective condition-monitoring device for power transformers.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.11
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• pp.743-750
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• 2012

An ultraviolet (UV) absorption method has a difficulty to analyze $ClO_{2(aq)}$ in solutions containing various chlorine species because UV spectrum of $ClO_{2(aq)}$ overlaps with other chlorine-containing species. This study has proposed the deconvolution method of UV spectrum to analyze $ClO_{2(aq)}$ concentration quantitatively in solution containing various chlorine species. We compared results obtained from UV deconvolution method with titration method. Good agreement of $ClO_{2(aq)}$ concentration between them has been shown in about 10%. This result informs us that the deconvolution method of UV spectrum could be a feasible for the analysis of $ClO_{2(aq)}$ in solution containing various chlorine species.

• Tribology and Lubricants
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• v.29 no.1
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• pp.51-55
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• 2013

In this work, a new fluorescence emission measurement technology was introduced and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate it for the oil oxidation measurement of electrical insulating oil. The oxidation characteristics of insulating oil were found to be fairly represented by the titration method and IR spectroscopy, and the results are comparable to a change in the fluorescence emission ratio that is defined as the shift in fluorescence intensity in the measured wavelength range. The result also shows that by the measurement of fluorescence emission ratio, it is possible to detect the oxidation of oil relatively earlier than by other methods. This study suggests that the developed technology can provide sufficient information for evaluating the insulating oil quality, and that the developed FER sensor can be used as an effective condition monitoring device of electrical insulating oil oxidation.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.793-799
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• 2011

We report the complexation behavior of calix[4]arenemonoquinone-triacid (CTAQ), which is an electroactive and water-soluble receptor for calcium ion. UV-visible and NMR spectroscopic studies revealed that CTAQ in aqueous media forms 1:2 as well as 1:1 (metal ion:CTAQ) stoichiometric complexes with $Ca^{2+}$, $Sr^{2+}$, and $Ba^{2+}$ ions. The nonlinear fitting of titration curves based on UV-visible absorption spectra showed that the binding constants of CTAQ for $Ca^{2+}$ ion are 4 $({\pm}2){\times}10^6\;M^{-1}$ for 1:1 and 1.4 $({\pm}0.5){\times}10^{11}\;M^{-2}$ for 1:2 complex. NMR conformational studies and the titration curves corroborate that the $Ca^{2+}$:CTAQ complex in aqueous solution is not present in the form of merely 1:1 one, being consistent with UV-visible spectrophotometric results. The Monte Carlo simulation supports the presence of a stable conformer of 1:2 complexes in which a $Ca^{2+}$ ion is interposed between two CTAQs at the global minimum. This is the first model of 1:2 stoichiometric complex of calix[4]arene and alkaline earth ions in aqueous media.

• BMB Reports
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• v.35 no.3
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• pp.302-305
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• 2002

Kinetic and thermodynamic studies have been made on the effect of the inosine product on the activity of adenosine deaminase in a 50 mM sodium phosphate buffer, pH 7.5, at $27^{\circ}C$ using UV spectrophotometry and isothermal titration calorimetry (ITC). A competitive inhibition was observed for inosine as a product of the enzymatic reaction. A graphical-fitting method was used for determination of the binding constant and enthalpy of inhibitor binding by using isothermal titration microcalorimetry data. The dissociation-binding constant is equal to $140\;{\mu}M$ by the microcalorimetry method, which agrees well with the value of $143\;{\mu}M$ for the inhibition constant that was obtained from the spectroscopy method.

• Bulletin of the Korean Chemical Society
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• v.29 no.3
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• pp.663-665
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• 2008

• Bulletin of the Korean Chemical Society
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• v.26 no.7
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• pp.1051-1056
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• 2005

The interaction of bovine carbonic anhydrase II with copper ions was studied by isothermal titration microcalorimetry, circular dichroism, UV spectrophotometry and temperature scanning spectrophotometry methods at 27 ${^{\circ}C}$ in Tris buffer solution at pH = 7.5. It was indicated that there are three non-identical different binding sites on carbonic anhydrase for $Cu^{2+}$. The binding of copper ions is exothermic and can induce some minor changes in the secondary and tertiary structure of the enzyme, which does not unfold it, but can result in a decrease in both activity and stability of the enzyme.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 1999.04a
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• pp.78-83
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• 1999

In this paper the extinction coefficients of molecule chlorine ($Cl_2$), chlorine dioxide (ClO$_2$), hypochlorous acid (HClO), chlorous acid ($HClO_2$$_2$) were determined using a PDA UV-VIS spectrophotometer. Based on these, the concentrations of $Cl_2$, $ClO_2$, and HClO in general chlorine dioxide bleaching liquor can be measured. The concentrations of $Cl_2$, $ClO_2$ and $HClO_2$ produced during the generation of methanol based chlorine dioxide generator can also be determined use the same method. The method was thought to be able to give more information in chlorine dioxide bleaching chemistry if combine its use with titration and ion chromatography.

• Analytical Science and Technology
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• v.8 no.3
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• pp.305-311
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• 1995

The stability constant of the complex between salicylic acid($H_2A$) and Fe(III) ion has been determined using UV-Vis absorption spectrometry and pH titration method in O.1M $KNO_3$ aqueous solution at $20^{\circ}C$ and compared with reference value, $logK_f=16.48$. The $pK_{a1}$ and $pK_{a2}$ of $H_2A$ are $2.92{\pm}0.08$ and $12.90{\pm}0.13$, respectively and the $logK_f$ of 1:1 complex Fe(III)-$H_2A$ system is $11.88{\pm}0.12$ at $20^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.1973-1977
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• 2009

In the present study, at first, 2,4-Dihydroxy Salophen (2,4-DHS), has been synthesized by combination of 1, 2-diaminobenzene and 2,4-dihydroxybenzaldehyde in a solvent system. This ligand containing meta-quinone functional groups were characterized using UV-Vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and 2,4-DHS, was investigated in 10 mM Tris/HCl buffer solution, pH 7.2, using UV-visible absorption and fluorescence spectroscopies, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of 2,4-DHS with ct-DNA was found to be (1.1 ${\pm}\;0.2)\;{\times}\;10^4\;M^{-1}.$ The fluorescence study represents the quenching effect of 2,4-DHS on bound ethidium bromide to DNA. The quenching process obeys linear Stern-Volmer equation in extended range of 2,4-DHS concentration. Thermal denaturation experiments represent the increasing of melting temperature of DNA (about 3.5 ${^{\circ}C}$) due to binding of 2,4-DHS. These results are consistent with a binding mode dominated by interactions with the groove of ct-DNA.