• 대한화학회지
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• 제39권1호
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• pp.57-65
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• 1995

$1.0{\times}10^{-2}M\; KNO_3$ 수용액에서 methylene blue(MB)의 전기화학적 환원을 직류 및 펄스차이 폴라로그래피, 순환 전압-전류법, 조절 전위 전기량법으로 조사하였다. MB의 전극환원은 처음 가역파(-0.18 volts vs. Ag/AgCl)에서 2전자 이동의 CE 반응기구로 진행되었다. Methylene blue는 정지된 수은전극에 강하게 흡착되었으며, 조절 전위 전기분해로 환원된 생성물은 공기중에서 빠르게 자동산화되어 본래의 MB로 돌아왔다. pH 변화에 따른 순환 전압-전류 그림과 폴라로그램의 해석을 근거로 하여 CE 반응기구를 제시하였다.

• 대한환경공학회지
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• 제28권6호
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• pp.667-676
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• 2006

환경 중에서 $Hg^{2+}$의 환원과정을 통하여 용존가스상 수은인 DGM(dissolved gaseous mercury)이 생성이 되고, 이 DGM의 대기로의 휘발이 수체에서의 중요한 이동 제거 기작이다. 아시아에서 배출하는 수은의 양이 전 세계적으로 큰 비중을 차지하는 것으로 알려져 있지만, 이 지역에 대한 DGM의 조사는 거의 없는 실정이다. 본 연구에서는 주암호를 대상으로 실시간으로 DGM 및 총 수은(TM) 농도변화를 관찰하였다. 연구 결과 여름철 주암호의 상류에서 하류까지 DGM 평균농도의 변화는 $95{\pm}8pg/L$에서 $130{\pm}15pg/L$로 증가했으나, TM의 평균농도는 상류지점 $2.1{\pm}0.7ng/L$, 하류지점 $1.7{\pm}0.3ng/L$로 낮아지는 경향을 보였다. 계절적인 DGM의 농도를 비교한 결과, 여름철 주암호의 총 DGM의 평균농도는 $109{\pm}15pg/L$로 가을철의 $19{\pm}pg/L3$ 보다 약 5.5배 높았다. 중류지점에서의 강우에 따른 DGM 평균농도의 변화는 비가 오기 전 32 pg/L에서 비가 내리는 동안 13.7 pg/L로 약 58% 감소했으며, TM은 2.2 ng/L에서 2.7 ng/L로 약 19% 증가했다. 가을철 상류지점의 일중 자외선과 DGM 평균농도의 변화는 빛의 강도와 비슷한 경향을 나타냈다. DGM의 농도와 수온, DOC의 농도 간의 통계적 분석결과는 유의한 상관관계(${\alpha}$=0.05)를 보였으나, TM의 농도는 반대의 상관관계를 나타냈다(p<0.0001). Dill et al.,(2006)의 연구와 비교한 결과, 주암호 총(n=23) DGM의 평균농도는 $109{\pm}15pg/L$로 국외 호수의 $38{\pm}16pg/L$보다 약 3배 높았고, TM의 평균 농도(n=11)는 $2.2{\pm}0.4ng/L$로 국외호수의 $1.0{\pm}1.2ng/L$ 보다 약 2.2배 높게 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.443-448
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• 1999

Tests have been carried out on four concrete containing different levels of silica fume to measure their permeability coefficient using water and oxygen, chloride ion. The total cementitious content was 351kg/㎥, and the water/cementitious materials ratio was 0.55. The results show that a dramatic reduction in permeability of concrete containing silica fume occurs due to formation of a discontinuous macro-pore system which inhibits flow. Porosity estimates from mercury-intrusion porosimetry are used to develop an explanations for the water and air permeability reduction. And, results of the rapid permeability test showed that the resistance of concrete to the penetration of chloride ions increases significantly as a contents of silica-fume is increased. The current intensity passing through the concrete containing silica fume is presented from 664C to 2166C.

• 대한화학회지
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• 제13권4호
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• pp.303-307
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• 1969

酸性溶液中에서 重金屬 이온의 沈澱劑로 널리 使用되는 Nitrosophenyhydroxylamine(Cupferron)의 非可逆電極反應의 電流電壓曲線과 酸性 및 알카리性에서의 還元反應機構 및 反應速度 그리고 pH變化에 따른 관여전자수, 活性化 energy를 Delahay 方法을 利用하여 구하였다.

• 대한화학회지
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• 제9권2호
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• pp.71-74
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• 1965

Reduction of Ti(Ⅳ)-oxalate complex on dropping mercury electrode has been studied as a function of oxalate concentration and of pH varied with HCl. Assuming there are equilibrium $TiO(C_2O_4)_2= \;+\;2H^+\;=\;Ti^{+4}\;+\;2C_2O_4\;=\;+\;H_2O,\;K_4$ in addition to $TiO(C_2O_4)_2\;^=\;=\;TiO^{++}\;+\;2C_2O_4=\;K_2\;Ti(C_2O_4)_2\;^-\;=\;Ti^{+3}\;+\;2C_2O_4=\;K_3$ in the system cathodic wave has been well explained for that pH is higher than 0.5. The equilibrium constants $K_2,\;K_3$ and $K_4$ have been to be $2{\times}10^{-12},\;5{\times}10^{-13}$ and $10^{-11}$, respectively. The reduction of Ti(Ⅳ)-oxalate system is $Ti^{+4}\;+\;e\;{\to}\;Ti^{+3}$ in the concentration of hydrochloric acid, higher than 3M.

• 한국환경보건학회지
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• 제27권2호
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• pp.82-91
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• 2001

This study was carried out to elucidate the protective effect of zinc chloride(ZnCl$_2$) and its mechanism against the immuno-cytotoxicity of methylmercury chloide($CH_3$HgCl). This study was observed in the culture of EMT-6 cells which are originated from mammary adenocarcinoma of Balb/c mouse. Cytotoxicity of metals was measured by cell viability and NO$_2$$^{[-10]}$ , and mitochondrial function was evaluated by adenosine triphosohate (ATP) production. $CH_3$HgCl significantly decreased the sythesis of nitric oxide(NO), ATP and glutathione(GSH) in a dose-dependent manner. ZnCl$_2$ significantly increased the synthesis of GSH in a dose-dependent manner, but synthesis of NO and ATP were not changed. The immuno-cytotoxicity of $CH_3$HgCl was not fully protected when combined addition of ZnCl$_2$, whereas ZnCl$_2$ prior to addition of $CH_3$HgCl completly protected the Hg-induced immuno-cytotoxicity. Similarly, intracellular accumulation of mercury significantly decreased by ZnCl$_2$. Degree of diminution of intracellular mercury was larger in ZnCl$_2$ prior to addition of $CH_3$HgCl than in combined addition of ZnCl$_2$ and $CH_3$HgCl.. Dithiothreitol(DTT) or buthionine sulfoximine(BSO) addition at 50$\mu$M or less, which was not toxic to the cells, did not affect synthesis of NO and ATP. DTT increased intracellular GSH level and DTT pretreatment protected toxicity induced by $CH_3$HgCl as shown complete recover in the NO and ATP values. BSO decreased intracellular GSH level and BSO pretreatment exaggerated toxicity induced by $CH_3$HgCl as shown synergistic reduction in the NO and ATP values. These results indicated that the protective effects of zinc against immuno-cytotoxicity of methylmercury associated with increasing cellular level of GSH. Increased intracellular GSH transports methylmercury to out of cells. In accordance with intracellular level of mercury decreased, immuno-cytotoxicity of methylmercury decreased. These result also suggest that the protective mechanism of zinc against the mercury toxicity would be exerted in the immune system in vivo.

• 한국환경보건학회지
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• 제47권3호
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• pp.245-258
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• 2021

Objectives: In many previous studies, endocrine disruptors (EDCs) have been found to affect delays in puberty. Various EDCs have been reported on, but there have been only limited epidemiologic studies on the effects of exposure to environmental heavy metals and pyrethroid pesticides on puberty delay. Therefore, the aim of this study was to investigate the association of exposure to environmental mercury, cadmium, and pyrethroid pesticides with delayed puberty in children based on national survey data that represents Korean children. Methods: We selected 450 children at the ages of 9-11 years old from the third Korean National Environmental Health Survey (3rd KoNEHS). The relations of urinary Hg, Cd, and 3-PBA with pubertal development were evaluated using multiple logistic regression analyses. Results: Urinary Hg levels were significantly associated with delayed puberty in boys [testicle development: OR=0.41 (95% CI: 0.20, 0.84); genitalia development: OR=0.35 (95% CI: 0.15, 0.81)]. Girls with higher Hg levels were more likely to experience delayed menarche [OR=0.23 (95% CI: 0.06, 0.90)]. We observed a significant 49% reduction in odds for menarche per increasing unit of urinary cadmium levels [OR=0.51 (95% CI: 0.24, 1.01)]. In addition, urinary 3-PBA showed a negative association with genitalia development in boys and menarche in girls [genitalia development: OR=0.73 (95% CI: 0.55, 0.96); menarche: OR=0.56 (95% CI: 0.32, 1.00)]. Conclusions: The results of this study support the hypothesis that exposure to environmental mercury, cadmium and pyrethroid pesticides may affect puberty delays. Additional evidence needs to be obtained through further prospective studies.

• Archives of Pharmacal Research
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• 제24권2호
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• pp.100-104
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• 2001

Differential pulse polarographic(DPP) analytical procedure for the rifampicin antibiotic, which can be applied to monitor its synthetic process from the starting antibiotic of rifamycin B or rifamycin SV has been developed based on the electrochemical reduction of an azomethine group. Rifampicin exhibited a cathodic peak due to the azomethine group in the side chain of 3-[(4-methyl-1-piperazinyl)imino]methyl moiety and another cathodic peak due to the carbonyl group in rifamycin SV by DPP. The experimental peak potential shift of an azomethine reduction was -73 mV/pH in the pH range between 3.0 and 7.5, agreeing with involvement of 4 e-and 5 $H^5$ in its reduction. By the cyclic voltammetric(CV) studies, the azomethine and the carbonyl reductions in rifampicin were processed irreversibly on the mercury electrode. The plot of peak currents vs. concentrations of rifampicin ranging $1.0{\times}10^{-7} M~$1.0{\times}10^{-5} M yielded a straight line with a correlation coefficient of 0.9996. The detection limit was $1.0{\times}10^{-8} M with a modulation amplitude of 50 mV DPP has been successfully applied for the determination of rifampicin in the pharmaceutical preparations.

• Bulletin of the Korean Chemical Society
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• 제14권5호
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• pp.567-574
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• 1993

Mordant Red 19(MR19) is reduced at mercury electrode at -0.67 V vs. Ag/AgCl with two electrons per molecule in pH 9.2 buffer by differential pulse polarography and linear sweep voltammetry. The peak potential is dependent on the pH of solution. The exhaustive electrolysis, however, gives 4 electrons per molecule because of the disproportionation of the unstable hydrazo intermediate. The electrochemical reduction of lanthanide-MR19 complexes is observed at more cathodic potential than that of free ligand. The difference in peak potentials between complex and free ligand varies from 75 mV for $La^{3+}$ to 165 mV for $Tb^{3+}$ and increases with increasing the atomic number of lanthanide. The electrochemical reduction of lanthanide complexes with MR19 is due to the reduction of ligand itself, and it can be potentially useful as an indirect method for the determination of lanthanides. The shape of i-E curves and the scan rate dependence indicates the presence of adsorption and the adsorption was confirmed by potential double-step chronocoulometry and the effect of standing time. Also the surface excess of the adsorbed species and diffusion coefficients are determined. The composition of the complex is determined to be 1 : 2 by spectrophotometric and electrochemical methods.

• 대한화학회지
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• 제33권2호
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• pp.215-224
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• 1989

$trans-[Co(en)_2X_2](ClO_4)_n$의 전극환원 반응메카니즘(X : 시아나이드, 나이트라이트, 암모니아, 그리고 이소티오시아네이트)을 순환전압전류법 및 폴라로그래피법으로 조사하였다. 수은전극일 때 Co(III)상태에서 Co(II) 상태로 되는 확산지배적인 1전자 비가역반응 이후에 착물의 분광화학적 흡수파가 큰 시아나이드가 배위된 착물은 (en), CN-가 해리되지 않았으며 전극반응 생성물이 전극에 흡착되었고, $NO_2\;^-,\;NH_3$는 해리되었다. 그 후 모든 Co(II) 착물상태가 금속상태로 2전자 비가역 과정으로 환원되면서 (en)이 해리되었다. 수은전극에서 $NO_2^-$가 배위된 착물은 ECE 반응기구이며 전극환원 후 $NO_2^-$가 해리되는 속도가 57${\sim}$100m sec 이상으로 측정되었다. 탄소전극일 때 이들 착물의 첫단계 환원은 확산지배적인 1전자 비가역 과정이며 분광학적 흡수파수가 증가할 때 환원 피이크전위$(-E_p)$가 증가하였다.