• Bulletin of the Korean Chemical Society
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• v.18 no.7
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• pp.706-710
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• 1997

Isotope ratios of K, Ca, Cr and Fe are measured at cool plasma condition generated using high carrier flow rate and relatively low RF power of 900 W. Background molecular ions are suppressed to below 100 counts which give isobaric interference to the analytes. The background ions show different attenuation characteristics at increased carrier flow rate and hence for each element different carrier flow rate should be used to measure isotope ratios without isobaric interference. Isotope ratios are measured at both scan and peak-hopping modes and compared with certified or accepted ratios. The measured isotope ratios show some mass discrimination against low mass due to low ion energy induced from a copper shield to eliminate capacitive coupling of plasma with load coil.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.546-551
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• 2024

As an effective methods of plasma heating, neutral beam injection (NBI) systems based on negative hydrogen ion sources will be utilized in future magnetic-confinement nuclear fusion experiments. Because of the collisions between the fast negative ions and the neutral background gas, the positive ions are inevitable created in the acceleration region in the negative NBI system. These positive ions are accelerated back into the ion source and become high energy backstreaming ions. In order to explore the characters of backstreaming ions, the track and power deposition of backstreaming H⁺ beam is estimated using the experimental and simulation methods at NNBI test facility. Results show that the flux of backstreaming positive ions is 1.93 % of that of negative ion extraction from ion source, and the magnet filed in the beam source has an effect on the backstreaming positive ions propagation.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.790-794
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• 2012

Trace metal ions such as $Cd^{2+}$, $Ni^{2+}$, and $Zn^{2+}$ in a highly saline sample were subjected to on-line complexation with 4-(2-thiazolylazo) resorcinol (TAR) dissolved in a background electrolyte (BGE) under transient isotachophoresis (TITP) conditions. A long plug of the saline sample, containing the trace metal ions but devoid of TAR, was injected into a coated capillary filled with a BGE composed of 150 mM 2-(cyclohexylamino) ethanesulfonic acid (CHES) and 110 mM triethylamine (TEA) at pH 9.7. Since the electrophoretic mobility of TAR fell between the mobilities of the anionic leading electrolyte ($Cl^-$ in the sample) and the anionic terminating background electrolyte ($CHES^-$), a highly concentrated zone of TAR from the BGE was formed at the rear of the sample matrix and then the metal cations toward the cathode were swept by isotachophoretically assisted on-line complexation (IAOC) between the metal ions and the isotachophoretically stacked TAR. As a result, anionic metal-TAR complexes were formed efficiently, which satisfy the TITP conditions between $Cl^-$ and $CHES^-$. The enrichment factors of metal ions including $Cd^{2+}$ were up to 780-fold compared to a conventional CZE mode using absorbance detection. The detection limits were 17 nM, 15 nM, and 27 nM for $Ni^{2+}$, $Zn^{2+}$, and $Cd^{2+}$ in a 250 mM NaCl matrix, respectively. Our method was successfully applied to the analysis of urine samples without desalting.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.59-66
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• 2005

A new ion transport code for planetary ionospheric studies has been developed with consideration of velocity differences among ion species involving ion-ion collision. Most of previous planetary ionosphere models assumed that ions diffuse through non-moving ion and neutral background in order to consolidate continuity and momentum equations for ions into a simple set of diffusion equations. The simplification may result in unreliable density profiles of ions at high altitudes where ion velocities are fast and their velocity differences are significant enough to cause inaccuracy when computing ion-ion collision. A new code solves explicitly one-dimensional continuity and momentum equations for ion densities and velocities by utilizing divided Jacobian matrices in matrix inversion necessary to the Newton iteration procedure. The code has been applied to Martian nightside ionosphere models, as an example computation. The computed density profiles of $O^+,\;OH^+$, and $HCO^+$ differ by more than a factor of 2 at altitudes higher than 200 km from a simple diffusion model, whereas the density profile of the dominant ion, $O_2^+$, changes little. Especially, the density profile of $HCO^+$ is reduced by a factor of about 10 and its peak altitude is lowered by about 40 km relative to a simple diffusion model in which $HCO^+$ ions are assumed to diffuse through non-moving ion background, $O_2^+$. The computed effects of the new code on the Martian nightside models are explained readily in terms of ion velocities that were solved together with ion densities, which were not available from diffusion models. The new code should thus be expected as a significantly improved tool for planetary ionosphere modelling.

• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.869-872
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• 2004

Newly synthesized 8-hydroxyquinoline based benzothiazole derivative 2 showed a distinctive $Hg^{2+}$-selectivity over other transition metal ions in aqueous solution. The fluorescence emission at 455 nm of 2 was completely quenched upon interaction with $Hg^{2+}$ ions in dioxane-$H_2O$ system (9 : 1, v/v). The selectivity was decreased in the order of $Hg^{2+}\;>>\;Cu^{2+}\;>\;Cd^{2+}\;>\;Pb^{2+}\;{\thickapprox}\;Zn^{2+}\;{\thickapprox}\;Ni^{2+},\;and\;Hg^{2+}$ concentration dependent fluorescence quenching profile was observed in the presence of common interfering metal ions as background. The fluorescence behavior of 2 suggests that the prepared compound could be used as a fluorescent signaling subunit for the construction of new $Hg^{2+}$-sensitive ON-OFF type supramolecular switching systems.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1409-1412
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• 2014

Sex hormones are important metabolites in vertebrates' development and reproduction. For rapid screening sex hormones, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) is one of the promising analytical platforms, but MALDI MS faces many challenges in detecting steroids such as low ionization efficiency and matrix background interference. One potential strategy to overcome matrix interference in the low m/z region is using a cyclodextrin (CD)-supported matrix for steroid analysis since CD-supported matrixes are known to effectively suppress matrix-related ion signals. In this study, we aimed to find the optimal CD-supported matrix for the analysis of the nonderivatized sex steroids. Our results showed that the ${\alpha}CD$-supported 2,5-dihydroxybenzoic acid (DHB) matrix efficiently ionized all three major classes of sex hormones, estrogens, androgens, and progestagens, with low or no matrix background and also with high sensitivity. In addition, the ${\alpha}CD$-supported DHB matrix mainly generated molecular ions or protonated ions of sex hormones, and this enabled us to obtain information-rich tandem mass spectra which potentially lead to unambiguous identification of steroid species from complex metabolite mixtures.

• Membrane and Water Treatment
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• v.11 no.1
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• pp.1-10
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• 2020

An understanding of particle-particle interactions in filtration requires studying the detachment as well as the attachment of nanoparticles. Nanoparticles captured in a granular media filter can be released by changing the physicochemical factors. In this study, the detachment of captured silver nanoparticles (AgNPs) in granular media filtration was examined under different ionic strengths, ion type, and the presence or absence of natural organic matter (NOM). Filtration velocity and ionic strength were chosen as the physical and chemical factors to cause the detachment. Increasing filtration velocity caused a negligible amount of AgNP detachment. On the other hand, lowering ionic strength showed different release amounts depending on the background ions, implying a population of loosely captured particles inside the filter bed. Overall detachment was affected by ionic strength and ion type, and to a lesser degree by NOM coating which resulted in slightly more detachment (in otherwise identical conditions) than in the absence of that coating, possibly by steric effects. The secondary energy minimum with Na ions was deeper and wider than with Ca ions, probably due to the lack of complexation with citrate and charge neutralization that would be caused by Ca ions. This result implies that the change in chemical force by reducing ionic strength of Na ions could significantly enhance the detachment compared to that caused by a change in physical force, due to a weak electrostatic deposition between nanoparticles and filter media. A modification of the 1-D filtration model to incorporate a detachment term showed good agreement with experimental data; estimating the detachment coefficients for that model suggested that the detachment rate could be similar regardless of the amount of previously captured AgNPs.

• Journal of Radiation Protection and Research
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• v.48 no.2
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• pp.77-83
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• 2023

Background: The purpose of this study is to purify uranium (U[VI])-contaminated soil-flushing effluent using the precipitation-distillation process for clearance. Precipitation and distillation are commonly used techniques for water treatment. We propose using a combination of these methods for the simple and effective removal of U(VI) ions from soil-flushing effluents. In addition, the U concentration (Bq/g) of solid waste generated in the proposed treatment process was analyzed to confirm whether it satisfies the clearance level. Materials and Methods: Uranium-contaminated soil was decontaminated by soil-flushing using 0.5 M sulfuric acid. The soil-flushing effluent was treated with sodium hydroxide powder to precipitate U(VI) ions, and the remaining U(VI) ions were removed by phosphate addition. The effluent from which U(VI) ions were removed was distilled for reuse as a soil-flushing eluent. Results and Discussion: The purification method using the precipitation-distillation process proposed in this study effectively removes U(VI) ions from U-contaminated soil-flushing effluent. In addition, most of the solid waste generated in the purification process satisfied the clearance level. Conclusion: The proposed purification process is considered to have potential as a soil-flushing effluent treatment method to reduce the amount of radioactive waste generated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.3
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• pp.194-197
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• 2002

Ion exchange is a chemical reaction between the ions in solution phase and ions in solid phase and is widely used in softening, demineralization, removal and collection of specific ions, and ion migration in the ground water. The ion selectivity depends on the charge and the hydrated radius of ion. The objective of this study was to examine the applicability of anion selectivity obtained from the ion exchange equilibrium OH/sup -/ < F/sup -/ < HCO/sup -/ < Cl/sup -/ < Br/sup -/ ≤ NO₃/sup -/ < SO₄/sup 2-/ to the column ion exchange. The column ion exchange was facilitated in the lower charge of counter-ion in the background electrolyte.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.470-470
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• 2010

Negative ions are generated in fusion edge plasmas, material processing plasmas, ionospheric plasmas. Analytic formulas for the deduction of the absolute density of negative ions was given by using the current-voltage(IV) characteristics of two electric probes at two different pressures [1], and negative ion density has been measured by one electric probe using the current-voltage characteristics of three different pressures [2]. Ratios of ion and electron saturation currents and electron temperatures and sheath areas of different pressures are usually incorporated into two equations with two unknowns for the negative ion density. In the previous publications, the sheath factor(sheath area, sheath density, sheath velocity) and effective masses of background ions with different pressures are qualitatively incorporated for the deduction of negative density. In this presentation, the quantitative and detailed relation of negative ion density with sheath factor and effective masses are going to be given. The effect of these parameters on the change of IV characteristics will be addressed.