• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.1
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• pp.20-25
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• 2015

Purpose: This study was evaluated the shade of feldspathic porcelain with various concentration of silver ion. Materials and Methods: The control group was conventional feldspathic porcelain with no silver ion, the experimental groups were the feldpathic porcelain with 5%, 10%, 20%, 30% silver ion. The number of specimens on the each group was 5. Commission Internationale de I'Eclairage (CIE) $L^*a^*b^*$ parameters were recorded twice for each specimen with a spectrophotometer (Model CM-2600d, Minolta, Japan). One-way Anova was used for statistical analysis. Results: L value was similar. a value was increasing and b value was decreasing with silver ion statistically significantly. ${\Delta}E$ was increasing according to silver ion significantly. Conclusion: The shade of feldspahtic porcelain was influenced by silver ion. Ag ion under 10% concentration is acceptable clinically.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.407-411
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• 1999

Studies have been carried out on the fabrication of PPy/GC and PPy/Pt electrode modified with polypyrrole film and determination of Cr(VI) by using 3-electrode system with modified electrodes. Modified electrodes were able to easily fabricated by cyclic voltammetry scanned from +1.0V to -1.0V(vs. Ag/AgCl) at 50 mV/sec. Film thickness could be controlled at same condition by the number of cycling up to 26 times. Reduction behaviour of Cr(VI) at PPy/GC electrode could be seen at wide potential ranges from +0.6V to -0.5V(vs. Ag/AgCl), and maximum reduction peak potential of the ion was observed at -0.25V(vs.Ag/AgCl). Calibration graph at its potential was linear from 0.1 ppm to 80.O ppm. Slope factor and relative coefficient were 1.75 mA/ppm and 0.998, respectively. Reduction behaviour of Cr(VI) at PPy/Pt electrode was similar to PPy/GC electrode, Calibration graph was linear from l.0 ppm to 60.0 ppm. Slope factor and relative coefficient were 0.5mA/ppm and 0.923, respectively. But PPy/GC modified electrode had about 3 times higher sensitivity than PPy/Pt modified electrode. Reduction behaviour of Cu(II), As(IlI), Pb(II), and Cd(II) couldn't be seen at PPy/GC electrode,Its metals had not lnterfered with Cr (VI) determination.

• Analytical Science and Technology
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• v.19 no.5
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• pp.383-388
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• 2006

Simple post-wash method by ion chromatography (IC) was established for the rapid and precise determination of fluoride ion in wastewater from mine in fluorite mineralized area. High sulfate in sample was retained in a pre-column and less strongly held fluoride ion was transferred to the principal separation system using modified conventional IC with switching technique. An analytical column with high capacity (AS 9 HC) was used as a pre-column to retain the amount of high sulfate. A guard column (AG 14) as a separation column was used to increase the response of fluoride and reduce the system pressure. According to the recovery of fluoride ion with one detector and the observation of sulfate peak with another conductivity detector, the optimum switching time of 10-port chromatographic injector was 4.3 min. The limit of detection (S/N = 3) of fluoride in synthetic solution containing $500mg\;L^{-1}$ sulfate was $2.4{\mu}g/L$, with $25{\mu}L$ sample volume.

• Korean Journal of Crystallography
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• v.16 no.2
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• pp.107-127
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• 2005

Five Cu(II) compounds were obtained from different copper salts with btp ligands, and their structures were determined by X-ray crystallography. The structure of coordination polymer 2 contains btp-bridged tetranuclear Cu(II) units weakly connected by nitrate ions, and the structure of a discrete Cu(II) molecule 1 contains acetates and btp ligands. With perchlorate anions, two btp ligands bridge Cu(II) ions to form a double zigzag chain 3, while a single zigzag chain 4 is created with sulfate anions. The reaction of $Cu(NO_{3})_{2}$ containing $NH_{4}PF_{6}$ with btp ligands also produced a polymeric compound 5 containing $Cu(H_{2}O)_{2}^{2+}$ and $Cu(NO_{3})_{2}$ units alternatively bridged by btp ligands with H-bonds between copper bonded water and nitrate oxygen atoms. Five Zn(II) compounds were obtained from different zinc salts with btp ligands, and the structures of polymeric compounds (6, 7 and 8) and monomeric compounds (9 and 10) were determined by X-ray crystallography. With nitrate, chloride and bromide anions, btp ligands bridge Zn(II) ions to form polymeric compounds (6, 7 and 8), but btp ligands coordinate to a Zn(II) ion to form monomeric complexes (9 and 10) with $PF_{6}^{-}$ and perchlorate anions. Four silver salts and btp ligands produced two kinds of structures, dinuclear 20-membered rings and one-dimensional zigzag chain depending on different anions. For $ClO_{4}^{-}$ and OTf anions, weak interactions between Ag(I) and anions make dinuclear 20-membered rings construct polymeric compounds (11 and 13). For $PF_{6}^{-}$ anion, there are also weak interactions between Ag(I) and $F(PF_{6}^{-})(12)$, but they do not construct a polymeric compound. For $O_{2}CCF_{3}^{-}$ anion, btp ligands bridge Ag(I) atoms to make one-dimensional zigzag chain (14), and there are also interactions between Ag(I) and anions.

• Journal of the Korean Chemical Society
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• v.37 no.11
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• pp.961-966
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• 1993

The determination of noble metals such as Ir, Au and Ag in the ancient coins has been studied. For the measurement of the activity of $^{192}Ir,\;^{198}Au\;and\;^{110m}Ag$, radiochemical separations including solvent extraction and ion-exchange chromatography were applied to reduce the interference of high energy ${\gamma}$-ray emitted from various radionuclides with long half-life. As a results, $10^{-11}$ g/g level of Ir could be detected and it was found that the three kinds of the detection limits, i.e., critical, detection, quantitative limit, calculated by the method proposed by Currie, were enhanced. Prior to the re-irradiation with neutron, inactive carrier was added in order to determine the recovery yield of Ir in the radiochemical separation. The average recovery yields of Ir, Au and Ag in the 5 coins were 65.3%, 98.5%, 99.5%, respectively.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.255-260
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• 2020

In this study, we developed a method of improving the surface-enhanced Raman spectroscopy (SERS) response characteristics by depositing a nanoporous Ag metal thin film through cluster source sputtering after forming a pyramidal texture structure on the Si substrate surface. A reactive ion etching (RIE) system with a metal mesh inside the system was used to form a pyramidal texture structure on the Si surface without following a complicated photolithography process, unlike in case of the conventional RIE system. The size of the texture structure increased with the RIE process time. However, after a process time of 60 min, the size of the structure did not increase but tended to saturate. When the RF power increased from 200 to 250 W, the size of the pyramidal texture structure increased from 0.45 to 0.8 ㎛. The SERS response characteristics were measured by depositing approximately 1.5 ㎛ of nanoporous Ag metal thin film through cluster sputtering on the formed texture structure by varying the RIE process conditions. The Raman signal strength of the nanoporous Ag metal thin film deposited on the Si substrate with the texture structure was higher than that deposited on the general silicon substrate by up to 19%. The Raman response characteristics were influenced by the pyramid size and the number of pyramids per unit area but appeared to be influenced more by the number of pyramids per unit area. Therefore, further studies are required in this regard.

• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3687-3691
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• 2011

Ion exchange experiments of molybdenum(VI) from strong HCl and $H_2SO_4$ solution have been done to investigate the existence of anionic complexes. The concentration of HCl and $H_2SO_4$was changed from 1 to 9 M. From the data on the complex formation of molybdenum in aqueous solution, a new distribution diagram of Mo(VI) was constructed in the pH range from zero to 10. AG 1 X-8, an anion exchange resin, and Diphonix, a cation exchange resin were used in the loading experiments. Ion exchange results indicate that anionic complexes of Mo(VI) begins to form from 3 M HCl and 1 M $H_2SO_4$ solution and the tendency to form anionic complexes is stronger in HCl than in $H_2SO_4$ solution. Our results can be utilized in the analysis of Mo(VI) in strong acid solution and in the design of a process to separate Mo(VI).

• Safety and Health at Work
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• v.12 no.2
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• pp.209-216
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• 2021

Background: The article presents the results of studies performed in order to develop a new method of airborne potassium bromate(V) determination at workplaces. Methods: The method is based on a collection of the inhalable fraction of potassium bromate(V) using the IOM Sampler, then extraction of bromates with deionized water and chromatographic analysis of the obtained solution. The analysis was performed using ion chromatography with conductometric detection. The tests were performed on a Dionex IonPac®AS22 analytic column (250 × 4 mm, 6 ㎛) with AG22 precolumn (50 × 4 mm 11 ㎛). Results: The method provides for potassium bromate(V) determination within the concentration range of 0.043 ÷ 0.88 mg/m³ for an air sample of 0.72 m³ in volume, i.e., 0.1-2 times the exposure limit value as proposed in Poland. The method was validated in accordance with PN-EN 482. The obtained validation data are as follows: measuring range: 3.1-63.4 ㎍/mL, limit of detection (LOD) = 0.018 ㎍/mL and limit of quantification (LOQ) = 0.053 ㎍/mL. The developed method has been tested in the work environment, on laboratory employees having contact with potassium bromate(V). Conclusion: The analytical method allowed the determination of the inhalable fraction of airborne potassium bromate(V) at workplaces and can be used to assess occupational exposure.

• BMB Reports
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• v.38 no.3
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• pp.294-299
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• 2005

In this report, we describe the high-yield secretory expression of the recombinant human anti-HBsAg Fab fragment from Pichia pastoris that was achieved by co-integration of the genes encoding the heavy and light chains (both under the control of alcohol oxidase promoter) into the genome of the yeast cells. The fed-batch fermentations were carried out in a 5 L scale. Both chains of the Fab were successfully expressed upon methanol induction. The absorbance ($OD_{600}$) of the broth can reach 350~500 at the end of fed-batch phase. After the induction, the expression level of the recombinant Fab (soluble) reached 420~458 mg/L. The recombinant Fab fragment was purified from the crude culture supernatant by ion exchange chromatography and the purity of the recombinant Fab fragment was over 95%. The affinity activities of the crude fermentation supernatant and the purified Fab were analyzed by indirect ELISA, which showed that the purified recombinant Fab fragment had high affinity activity with hepatitis B surface antigen.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.1
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• pp.31-47
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• 1989

The purpose of this study was to evaluate the chemical bond strength of successively recast Pd-Ag ceramic alloys with porcelain and to investigate changes of quantity of trace elements at the metal-porcelain interface. Porcelain was fired as usual manner on the each successively recast specimen. Rectangular planar shear test was performed and bond strength was measured by Instron universal testing machine. Diffusion of trace elements at the each interface was observed by ESCA (Electron Spectroscopy for Chemical Analysis). The obtained results were as follows : 1. Chemical bond strength was significantly decreased after second recasting. But in case of first recasting, there was no significant decrease of bond strength statistically (p<0.05). 2. Bond strength was not significantly decreased in each generation, when fifty percents new alloy was added (p<0.05). 3. Ag, Sn and In were observed at the porcelain interface. But Pd was not observed. 4. The quantity of Ag, In ions were progressively increased at the metal-porcelain interface as the casting was repeated. Silver ion was most significantly increased.