• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.753-757
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• 2014

The nucleophilic substitution reactions of Y-aryl N,N-dimethyl phosphoroamidochloridates with substituted anilines and deuterated anilines are kinetically investigated in acetonitrile at $65.0^{\circ}C$. A stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed based on the positive ${\rho}_{XY}$ value. The deuterium kinetic isotope effects involving deuterated anilines show secondary inverse with all the nucleophiles, rationalized by a dominant backside nucleophilic attack.

• 전기의세계
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• v.13 no.1
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• pp.30-33
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• 1964

최근 우리나라의 isotope사용은 의학 및 농학을 비롯하여 여러 분야에서 활발히 움직이고 있으나 공업면의 응용에는 아직 거의 없는 실정에 놓여있는 것이다. 그것은 계측기의 성능이 종래의 다른 방식과 비교할 때 대단히 우수하여 계측만으로의 목적으로는 좋은 평가를 받았든 것이나 process공업의 목적으로는 측정 절단 그리고 제어를 하는 복잡한 체계로서 시작하여야 되는 고로 다소 고도의 기술을 요하는 난점이 있었기 때문이었다. 따라서 본지에서는 실제 isotope가 process공업에 응용될때 문제되는 점 즉 process제어 정밀도의 우려를 가려내는 검출단의 성능과 각 공업에서 사용할 수 있는 계측기의 제어계를 간단히 해설하여 보기로 한다.

• Bulletin of the Korean Chemical Society
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• v.29 no.11
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• pp.2125-2128
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• 2008

• Proceedings of the KSEEG Conference
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• 2003.04a
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• pp.20-23
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• 2003

Low-sulfidation style ore deposits, the major source of Au, Ag, and Hg, are formed from neutral-pH, reduced hydrothermal solutions close to equilibrium with their host rocks. The waters are low-salinity (〈1 wt % NaCl equiv.) but relatively gas rich (1-2 wt % $CO_2$), and are largely meteoric water. However, the contribution of magmatic components to the epithermal system, its temporal importance, and its relation to the source of ore metals are largely controversial. (omitted)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.407-408
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• 2001

Stable isotope technique in matrine science is becoming powerful tool to roveal the environmental characteristics surrounding organisms during their past life histories. general, the isotopic data can be used for estimations of habitat temperature, migratory patterns and habitat location, metabolic rates, and investigations of food chains (Kalish, 1991). (omitted)

• Journal of the Korean Chemical Society
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• v.63 no.5
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• pp.387-391
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• 2019

• Journal of the korean veterinary medical association
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• v.9 no.3
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• pp.67-70
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• 1965

• Economic and Environmental Geology
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• v.33 no.6
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• pp.469-489
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• 2000

The hydrogeochemical and isotopic studies on deep groundwater (below a 550 m depth from the ground surface) in the Munkyeong area, Kyeongbuk province were carried out. Two types of deep groundwater (${CO_2}$-rich groundwater and alkali groundwater) occur together in the Munkywong area. ${CO_2}$-rich groundwater (Ca-${HCO_3}$ type) is characterized by low pH (5.8~6.5) and high TDS (up to 2,682 mg/L.), while alkali groundwater (Na-${HCO_3}$ type) shows a high pH (9.1~10.4) and relatively low TDS (72~116 mg/L). ${CO_2}$-rich water may have evolved by ${CO_2}$ added at depth during groundwater circulation. This process leads to the dissolution of surrounding rocks and Ca, Na, Mg, K and ${HCO_3}$ concentrations are eniched. The low $Pco_2$ ($10^{-6.4}$atm) of alkali groundwaters seems to result from the dissolution of silicate minerals without a supply of ${CO_2}$. The ${\delta}^{18}O$ and ${\delta}^D$values and tritium data indicate that two types of deep groundwater were both derived from pre-thermonuclear meteoric water and have evolved through prolonged water-rock interaction. The carbon isotope data show that dissolved carbon in the ${CO_2}$-rich water was possibly derived from deep-seated ${CO_2}$ gas, although further studies are needed. The ${\delta}^{34}S$ values of dissolved sulfate show that sulfate reduction occurred at great depths. The application of various chemical geothermometers on ${CO_2}$-rich groundwater shows that the calculated deep reservoir temperature is about 130~$l75^{\circ}C$. Based on the geological setting, water chemistry and environmental isotope data, each of the two types of deep groundwater represent distinct hydrologic and hydrogeochemical evolution at depth and their movement is controlled by the local fracture system.

• Analytical Science and Technology
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• v.27 no.3
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• pp.140-146
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• 2014

An internal standard was used in PCID (post column isotope dilution) to improve the accuracy and precision in quantification of various chemical species. The error occurring in the column was the largest in HPLC-ICP/MS (high performance liquid chromatography-inductively coupled plasma/mass spectrometry) when PCID and other traditional quantification methods were compared with each other. Internal standard was effective in correcting the loss of sample in the column to improve accuracy and precision. When applied to SeMet, using MeSecys or $Se^{4+}$ as an internal standard, relative errors were reduced from 31% and 13% to less than 1%, while standard deviations were reduced from 5.1% and 6.9% to 1.5% and 0.2%, respectively. Positive aspects of using an internal standard in PCID were compared with other quantitative techniques and discussed in detail.

• Mass Spectrometry Letters
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• v.3 no.2
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• pp.54-57
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• 2012

Mass spectrometric analysis was carried out using multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for the precise and accurate determination of the isotope ratios of ultratrace levels of uranium dissolved in 3% $HNO_3$. We used the certified reference material (CRM) 112-A at a trace level of 100 pg/mL for the uranium isotopic measurement. Multiple collectors were utilized for the simultaneous measurement of uranium isotopes to reduce the signal uncertainty due to variations in the ion beam intensity over time. Mass bias correction was applied to the measured U isotopes to improve the precision and accuracy. Furthermore, elemental standard solution with certified values of platinum, iridium, gold, and thallium dissolved in 3% $HNO_3$ were analyzed to investigate the formation rates of the polyatomic ions of $Ir^{40}$ $Ar^+$, $Pt^{40}$ $Ar^+$, $Tl^{40}$ $Ar^+$, $Au^{40}$ $Ar^+$ for the concentration range of 50-400 pg/mL. Those polyatomic ions have mass-to-charge ratios in the 230-245 m/z region that it would contribute to the increase of background intensity of uranium, thorium, plutonium, and americium isotopes. The effect of the polyatomic ion interference on uranium isotope measurement has been estimated.