• 대한화학회지
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• 제19권3호
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• pp.179-185
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• 1975

방향족 치환반응을 모형과하여 유사분자 착물이 천이상태가 될수있음을 단수 Huckel법으로 증명하고 새로운 방향족 치환반응의 기구를 제안하였다. 아울러 이 유사분자 착물을 양자역학적 선동법을 이용하여 안정화 에너지식을 유도하고 많은 탄소화합물의 안정화 에너지식을 유도하고 많은 탄소화합물의 안정화 에너지를 구하였다. 이 안정화 에너지로 어떤 방향족 화합물이 유사분자 착물을 형성하는 위치와 그 화합물의 치환반응의 결합 시약이 방향족 화합물에 부가반응이 일어나는 반응에까지 널리 설명할 수 있는 이점이 있다.

• 분석과학
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• 제32권4호
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• pp.121-130
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• 2019

Alumina is one of the most important ceramic materials because of its useful physical and chemical properties. Recently, high-purity alumina has been used in various industrial fields. This leads to increasing demand for reliable elemental analysis of impurities in alumina samples. However, the chemical inertness of alumina makes the sample preparation for conventional elemental analysis a tremendously difficult task. Herein, we demonstrated the feasibility of laser ablation for effective sampling of alumina powder. Laser ablation performs sampling rapidly without any chemical reagents and also allows simultaneous optical emission spectroscopy and mass spectrometry analyses. For six alumina samples including certified reference materials and commercial products, laser-induced breakdown spectroscopy (LIBS) and laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) analyses were performed simultaneously based on a common laser ablation sampling. LIBS was found to be useful to quantify alkali and alkaline earth metals with limits-of-detection (LODs) around 1 ppm. LA-ICP-MS could quantify transition metals such as Ti, Cu, Zn, and Zr with LODs in the range from a few tens to hundreds ppb.

• 한국환경보건학회지
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• 제33권2호
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• pp.150-157
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• 2007

The chemical and photochemical decolorization of Rhodamine B (RhB) in water has been carried out by Fenton, Fenton-like and photo-Fenton-like process. The effect of applied $H_2O_2,\;Fe^{2+}$ dosage (Fenton process), $H_2O_2,\;Fe^{\circ}$ dosage (Fenton-like and photo-Fenton-like process), UV light power (photo-Fenton-like process) pH (all processes) have been studied. The results obtained showed that more than 98% of color removal was obtained for the RhB solutions in every process. However, Fenton-like process was not suitable for the color removal of RhB because Fenton-like process was required much more reagents than Fenton and photo-Fenton-like process. The Fenton and photo-Fenton-like process showed similar reagents need. Optimum pH for three processes in this study is about pH 3. The relative order of sensitivity for pH of each process was: Fenton-like > photo-Fenton-like > Fenton.

• 대한방사성의약품학회지
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• 제6권2호
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• pp.146-154
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• 2020

Selective installation of proteins using chemical reagents is important for the development of potential biomaterials for the treatment of human diseases. However, modification in a chemo- and regioselective manner under physiological conditions is a great challenge due to the presence of multiple reactive centers in the protein. Currently, the majority of conjugations are limited to lysine (Lys)- and cysteine (Cys)-selective reagents. Thus, they have been extensively studied. Apart from Lys and Cys, widespread site selectivity has been recently achieved through most of the 20 naturally occurring amino acid-bearing reactive functional groups. Consequently, this review focused on several recent achievements in site-selective modification of the rarest amino acid backbones (e.g., methionine, serine, glutamic acid, and tyrosine).

• Bulletin of the Korean Chemical Society
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• 제34권6호
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• pp.1745-1750
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• 2013

A novel green aqueous mobile phase modified with room temperature ionic liquids (RTILs) was employed in the absence of volatile organic solvents or ion-pairing reagents to analyze thiamine, a very polar compound, by reverse phase high performance liquid chromatography (RP-HPLC). Due to its strongly hydrophilic nature, thiamine was eluted near the column dead time ($t_0$) using a mobile phase without adding RTILs or ion-pairing reagents, even if a 100% aqueous mobile phase, which has weak elution power under reverse phase conditions, was used. Thus, 1-ethyl-3-methyl-imidazolium hexafluorophosphate ([EMIM][$PF_6$]), which has the strongest chaotropic effect, was selected as a mobile phase additive to improve retention and avoid baseline disturbances at $t_0$. Various mobile phase parameters such as cation moiety, chaotropic anion moiety, pH and concentration of RTILs were optimized to determine thiamine at the proper retention time. Method validation was performed to assess linearity, intra- and inter-day accuracy and precision, recovery and repeatability; all results were found to be satisfactory. The developed method was also compared to the current official United States Pharmacopoeia (USP) and Korean Pharmacopoeia (KP) methods using an organic mobile phase containing an ionpairing reagent by means of evaluating various chromatographic parameters such as the capacity factor, theoretical plate number, peak asymmetry and tailing factor. The results indicated that the proposed method exhibited better efficiency of thiamine analysis than the official methods, and it was successfully applied to quantify thiamine in pharmaceutical preparations.

• 상하수도학회지
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• 제29권4호
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• pp.481-491
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• 2015

The aim of this study was to evaluate the chemical quenching system for residual ozone and to determine the operating condition for the quenching system. Hydrogen peroxide ($H_2O_2$) and sodium thiosulfate ($Na_2S_2O_3$) were investigated as quenching reagents for ozone removal, and the tendency of each chemical was notably different. In the case of $H_2O_2$, the degradation rate of ozone was increased as the concentration of $H_2O_2$ increase, and temperature and pH value have a significant effect on the degradation rate of ozone. On the other hand, the degradation rate of ozone was not affected by the concentration of $Na_2S_2O_3$, temperature and pH value, due to the high reactivity between the ${S_2O_3}^{2-}$ and ozone. This study evaluates the decomposition mechanism of ozone by $H_2O_2$ and $Na_2S_2O_3$ with consideration for the water quality and reaction time. Furthermore, the removal test for the quenching reagents, which can be remained after reaction with ozone, was conducted by GAC process.

• 분석과학
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• 제25권5호
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• pp.284-291
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• 2012

혈흔지문은 매우 중요한 증거물이다. 본 실험은 지류에 유류된 혈흔지문에 대해 화학시약인 닌히드린, leucocrystal violet (LCV), fuchsin acid, 요오드, dimethylaminocinnam aldehyde (DMAC) 시약들의 증강효과를 확인한 것이다. 혈흔지문은 종이에 순차적으로 유류시킨 후 실온에서 건조해 사용하였다. 혈흔지문 융선이 비교적 선명할 경우에는 닌히드린과 LCV 시약이 가장 효과적이었지만, 눈에 보이지 않는 융선에 대한 증강효과는 크지 않았다. Fuchsin acid 시약을 사용하면 종이 표면이 염색되므로 혈흔지문의 contrast는 오히려 감소했다. 요오드 시약으로 혈흔지문 융선이 증강되긴 했지만, 반응 후 발색이 약하고 증강효과도 크지 않았다. DMAC 시약은 선명한 혈흔지문에 대한 증강효과가 좋지 않았지만, 희미한 융선에 대한 증강에는 매우 효과적이었다. 메탄올로 세척함으로서 DMAC로 증강된 혈흔지문의 contrast를 높일 수 있었다.

• 한국산업융합학회 논문집
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• 제7권1호
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• pp.107-113
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• 2004

Several transition metal complexes, [$M(L)X_2$](M=Pd(II), Ni(II); X=CI, Br) are prepared with aminophosphine ligands such as 1,2-bis{(diphenylphosphino)amino}ethane{$Ph_2PNHCH_2CH_2NHPPh_2$}($L_1$), 1,2-bis{(diphenylphosphino)amino}propane{$Ph_2PNHCH(CH_3)CH_2NHPPh_2$}($L_2$), trans-1,2-bis{(diphenylphosphino)amino}cyclohexane{$Ph_2PNHC_6H_{10}NHPPh_2$}($L_3$) and 1,2-bis{(diphenylphosphino)amino}benzene{$Ph_2PNHC_6H_4NHPPh_2$}($L_4$). The properties of these complexes are characterized by optical spectroscopic methods including UV/vis spectroscopy, CD, IR, $^1H$- and $^{31}P-NMR$ together with conductometer and elemental analysis. All complexes are stable under atmospheric environment. Catalytic reactivity for C-C coupling between [$M(L)X_2$] and Grignard reagents(RMgX; R=phenyl, propyl, buthyl) by thermolysis were investigated utilizing GC/mass, $^1H$- and $^{13}C-NMR$. When mol scale is 1:20 at [$Pd(L)Cl_2$] and Grignard reagents, the high catalytic activity for C-C coupling is apparent. The [$M(L)X_2$](X=Cl, Br) complexes which have strong bond at M-P exhibit high yields for C-C coupling reactions. When the central metal ion is Pd(II), the high catalytic activity for C-C coupling is apparent. The complex coordinated with Br shows higher catalytic activity for C-C coupling reactions compared to Cl.

• 생명과학회지
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• 제15권4호
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• pp.633-640
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• 2005

Bacillus pumilus TX703으로부터 xylanase를 정제한 후 효소의 활성부위를 조사하기 위하여 여러 가지 화학수식제를 사용하여 효소활성의 저해도를 측정하였다. 여러 가지 화학수식제 중에서 carbodiimide와 N-bromosuccinimide가 효소활성을 완전히 저 해시 켜 glutamic acid 또는 aspartic acid 잔기와 tryptophan 잔기가 효소의 활성부위에 관여하리라 추측되었다. 각각의 경우에 효소 실활은 수식제의 첨가농도에 따라 pseudo first-order kinetics 양식을 보여주었으며, car-bodiimide와 N-bromosuccinimide는 각각 비경쟁적 저해와 경쟁적 저해방식을 나타내었다. 기질첨가에 의한 효소활성 보호실험을 통하여 tryptophan 잔기가 기질결합부위라 판단되었다. 효소실활속도의 분석에 의해 효소활성에는 2개의 glutamic acid 또는 aspartic acid 잔기와 1개의 tryptophan 잔기가 관여하는 것으로 나타났다.

• Bulletin of the Korean Chemical Society
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• 제26권11호
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• pp.1692-1694
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• 2005

Spent nuclear fuel is reprocessed commercially by the chemical process to recover U and Pu. Recently, new salt-free reagents to separate plutonium and neptunium from uranium suitable for use in a single cycle flowsheet have been developed. Acetohydroxamic acid $(CH_3CONHOH)$ has been taken much interest in as a complexing agent capable of selective stripping of tetravalent actinides from U(VI) when actinides are present in the solvent stream of the advanced PUREX process. Additionally acetohydroxamic acid will rapidly reduce Np(VI) to inextractable Np(V) thus allowing the separation of Np from U. In this study, the rate equation for the reduction of Np(VI) to Np(V) in nitric acid aqueous solution has been determined as: $-[NpO_2^{2+}]$/dt = $k[NpO_2^{2+}]$[AHA] with k = 191.2 ${\pm}$ 11.2 $M^{-1}s^{-1}$ at 25 ${\pm}$ 0.5 ${^{\circ}C}$ and $[HNO_3]$ = 1.0 M. Comparison with other reductants available in the literature, acetohydroxamic acid is a strong one for $NpO_2^{2+}$.