• Journal of the Korean Chemical Society
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• v.36 no.3
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• pp.412-418
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• 1992

The electrochemical behaviors and analytical application of copper-1,5,9,13-tetrathiacyclohexadecane[16-ane-$S_4$] complex in acetonitrile(AN) solution have been investigated by the use of DC polarography and differential pulse polarography. Thus the formation constant of copper complex was $10^{3.51}$. Copper (Ⅱ) ion was found to form complex of 1-to-1 composition with [16-ane-$S_4$]. In addition, reduction step was irreversible and the reduction current was diffusion controlled. And the effect of concentration of the salting-out reagent and chelating agent and pH of aqueous phase on the determination of copper (Ⅱ) was investigated and diverse ion effect was discussed. By salting-out extraction technique, we can be determined until the concentration of copper (Ⅱ) of 60 ppb.

• Mass Spectrometry Letters
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• v.4 no.4
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• pp.67-70
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• 2013

The Cu-binding site in the $[Cu{\cdot}dCMP{\cdot}dCMP-H]^{1-}$ complex was investigated. The tandem mass (MS/MS) spectra of the [$[Cu{\cdot}dCMP{\cdot}dCMP-H]^{1-}$ parent ion showed $[dCMP{\cdot}Cu{\cdot}H_2PO_4+CONH]^{1-}$ fragment ions. Therefore, we propose that the Cu cation is simultaneously coordinated to the phosphate site and cytosine moiety in the stable geometry of the $[Cu{\cdot}dCMP{\cdot}dCMP-H]^{1-}$ complex. Three geometries for the complex were considered in an attempt to optimize the structure of the $[Cu{\cdot}dCMP{\cdot}dCMP-H]^{1-}$ complex. The ab initio calculations were performed at the $B3LYP/6-311G^{**}$ level.

• Journal of Pharmaceutical Investigation
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• v.19 no.2
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• pp.99-107
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• 1989

In order to develop a pediatric liquid preparation with sustained release properties, dextromethorphan hydrobromide (DEXT) was complexed with strong cation exchange resin (CG 120) and the-complex was coated with Eudragit RS using a phase separation method by non-solvent addition. The effect of pH, ionic strength of the release medium and drug/resin ratio on the release rate of DEXT was studied. The release rate of free drug from the uncoated complex, and coated complexes with 9.5 and 18.5% Eudragit RS in artificial gastric juice were measured. The release rate from the uncoated complex was faster with higher pH, higher ionic strength of the release medium and higher drug/resin ratio. The release rate from the coated complex could be controlled by the amount of coating material, and the surface after release did not rupture into.

• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.645-651
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• 2005

• Proceedings of the Korea Crystallographic Association Conference
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• 2000.11a
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• pp.17-17
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• 2000

• Proceedings of the PSK Conference
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• 2001.10a
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• pp.282.3-283
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• 2001

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.485-488
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• 1999

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.117-121
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• 2008

Pseudo-first-order rate constants (kobsd) have been measured spectrophotometrically for nucleophilic substitution reactions of 5-nitro-8-quinolyl benzoate (5) with alkali metal ethoxides, EtO?M+ (M+ = Li+, Na+ and K+) in anhydrous ethanol (EtOH) at 25.0 0.1 C. The plots of kobsd vs. [EtO?M+] exhibit upward curvatures, while the corresponding plots for the reactions of 5 with EtO?Na+ and EtO?K+ in the presence of complexing agents, 15-crown-5-ether and 18-crown-6-ether are linear with rate retardation. The reactions of 5 with EtO?Na+ and EtO?Li+ result in significant rate enhancements on additions of Na+ClO4, indicating that the M+ ions behave as a catalyst. The dissociated EtO and ion-paired EtOM+ have been proposed to react with 5. The second-order rate constants for the reactions with EtO (kEtO) and EtOM+ (kEtOM+) have been calculated from ion-pairing treatments. The kEtO and kEtOM+ values decrease in the order kEtONa+ > kEtOK+ > kEtOLi+ > kEtO, indicating that ion-paired EtOM+ species are more reactive than the dissociated EtO ion, and Na+ ion exhibits the largest catalytic effect. The M+ ions in this study form stronger complex with the transition state than with the ground state. Coordination of the M+ ions with the O and N atoms in the leaving group of 5 has been suggested to be responsible for the catalytic effect shown by the alkali metal ions in this study.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.171-177
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• 1993

In decontamination process to remove radioactive materials of reactor cooling system, the metal ions dissolved by organic acids in decontamination solution are separated by use of ion exchange resin in the column. However, organic acids in decontamination solution decrease the apparent affinity of the resin to metal ions. In light of this, some experiments were carried out on the Amberlite IRN-77 cation resin with cobalt and iron to gain a better understanding of the complexation effects on the ion exchange process. Experimental results showed that EDTA among organic acids used as chemical decontaminants predominantly caused reduction of ion exchange capacity of cobaltous ion to resin since this reagent formed the complex with the cobaltous ion stronger than that with the ferrous ion. In contrast, the effects of oxalic acid and citric acid were found to be negligible. And, single and two-component nonlinear equilibrium relationships of the metal ions were established using experimental data.

• Journal of the Korean Chemical Society
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• v.31 no.1
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• pp.45-54
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• 1987

Dowex 1-X8 resin ion exchanged with calcon carboxylic acid (CCA-Dowex 1-X8) and 2-methyl-8-hydroxyquinoline(MHQ) impregnated-Amberlite XAD-4 resin (MHQ-XAD-4) were examined for the separation and preconcentration of ferric ion from the various matrices. The stabilities of these resins were investigated, and their capacities on ferric ion were also measured. The effect of pH on the adsorption of ferric ion and matrix ions, such as Al(Ⅲ) and Ca(Ⅱ), was investigated to determine the optimun pH ranges. Separation and preconcentration of iron in aluminium foil and mineral water samples were studied by elution method with these resin columns. The recovered ions by 10ml of 2F nitric acid was determined by flame atomic spectrophotometry. SP-Sephadex C-25 column was used to separate ferrous and ferric ion in mineral water by stepwise elution with ferrozine and 1 % ascorbic acid-ferrozine solution. The concentrated and separated each ion could be determined spectrophotometrically at the analytical wavelenth of Fe(Ⅱ)-ferrozine complex (562nm).