• Restorative Dentistry and Endodontics
• /
• v.10 no.1
• /
• pp.71-83
• /
• 1984

The purpose of this study was to evaluate the transmission spectrum of the set calcium hydroxide dental cement (Dycal, L.D. Caulk Co. Milford, Del.) Cement was prepared for A T R spectra at a low powder-to-liquid ratio of 3.0gm/ml in order to retard the reaction and facilitate the manipulation of loading the cement into the cell. Spectra were recorded on an I R Spectrophotometer (MX-1, FT) at an agle of incidence of 55. The A T R cell was a RIIc Model TR5 with a hemisperical KRS-5 (Thallium-Bromide-Iodide). A spectrum was recorded within 3 minutes. Further spectra were recorded after 5,10,30 minutes and 1,5,24, 72 hours. The results were as follows; 1. The setting reaction between acid paste and base past would take place fastly within 10 minutes after mix, and that would be slow until 72 hours after mix. 2. In the set cements, some methyl salicylate and calcium hydroxide remained unreacted until 72 hours after mix. 3. The setting reaction and the reaction rate occuring at the surface and in the bulk cements were similar. 4. The chelates were bound together between calcium hydroxide and methyl salicylate.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.7
• /
• pp.2229-2237
• /
• 2012

The two chelates based on calix[4]arene and thiacalix[4]arene have been synthesized and used as neutral ionophores for preparing PVC based membrane sensor selective to $Ho^{3+}$ ion. The addition of potassium tetrakis(4-chlorophenyl)borate (KTpClPB) and various plasticizers, viz., NDPE, o-NPOE, DOP, TEP and DOS have been found to improve significantly the performance of the sensors. The best performance was obtained with the sensor no. 6 having membrane of $L_2$ with composition (w/w) ionophore (2%): KTpClPB (4%): PVC (37%): NDPE (57%). This sensor exhibits Nernatian response with slope $21.10{\pm}0.3mV/decade$ of activity in the concentration range $3.0{\times}10^{-8}-1.0{\times}10^{-2}M\;Ho^{3+}\;ion$, with a detection limit of $1.0{\times}10^{-8}M$. The proposed sensor performs satisfactorily over a wide pH range of 2.8-10, with a fast response time (5 s). The sensor was also found to work successfully in partially non-aqueous media up to 25% (v/v) content of methanol, ethanol and acetonitrile, and can be used for a period of 4 months without any significant drift in potential. The electrode was also used for the determination of $Ho^{3+}$ ions in synthetic mixtures of different ions and the determination of the arsenate ion in different water samples.

• Bulletin of the Korean Chemical Society
• /
• v.14 no.1
• /
• pp.59-62
• /
• 1993

Spectrophotometric determination of some heavy lanthanide ions by flow injection method is described. Xylenol Orange forms water soluble chelates with lanthanide ions in a tris[hydroxymethyl]-aminomethane-buffered medium having pH 8.3 and containing cetyltrimethylammonium bromide. The molar absorptivities of Ln(III)-XO complexes were increased by the ternary system with cetyltrimethylammonium bromide with the concomitant bathochromic shift of absorption maxium compared to those of the binary system without cetyltrimethylammonium bromide. The calibration curves are linear in the range 0.25-1.00 ppm for Gd(III), Dy(III), Er(III), Tm(III) and Yb(III) and the dynamic range are very wide. The detection limits (S/N=2) are from 2 ppb for Gd(III) to 30 ppb for Yb(III) and the relative standard deviations are from 1.2% for 0.5 ppm Gd(III) to 1.8% for 0.5 ppm Yb(III). The sample throughput was ca. 50 $h^{-1}$.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.4
• /
• pp.457-462
• /
• 1998

A chiral pentadentate bis-amide ligand, 1,9-bis(S)-pyrrolidinyl-2,5,8-triazanonane-1,9-dio ne$(S,S-prodienH_2)$ has been synthesized from the reaction of bis(2-aminoethyl)amine(dien) and S-proline, and the structure of $[Co(S,S-prodien)H_2O]ClO_4$ has be en determined by single crystal X-ray diffraction. The geometrical structure of the Co(III) complex has been an αβ -form, where the dien moiety of ligand chelates to a facial in metal center, and the aqua ligand coordinates a cis site to the secondary nitrogen of dien. The Co-N(1), Co-N(3) distances of two amide moiety in S,S-prodien are shorter than the other Co-N(2), Co-N(4), and Co-N(5) distances because of the increased basicity of nitrogen in amide. The complex crystallizes in the monoclinic space group $P2_1$(#4), with a=7.838(1), b=12.675(1), c=9.710(1) Å, β=100.39(1) and z=2. Refinement gives the final R and $R_w$ values of 0.045 and 0.057, respectively for 2130 observed reflections. Based upon the CD and X-ray data, it is identified that the absolute configuration of the αβ -$[Co(S,S-prodien)H_2O]ClO_4$ has a Λ-form.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.6
• /
• pp.648-652
• /
• 1999

Studies have been carried out on the unusual molecular nonrigidity of CoⅢ(PymS)3 and Cp* RhⅢ(PymS)2(PymS:2-mercaptopyrimidine). The crystal structure of CoⅢ(PymS)3 approximates to an octahedral mer isomer with 4-membered N-Schelating fashion. For Cp*RhⅢ(PymS)2, one PymS ligand bonds to the rhodium ion in an S-monodentate mode (Rh-S(2) = 2.366(1)Å) while the other ligand chelates to the metal ion in an N,S-bidentae mode (Rh-S(1)=2.414(1);Rh-N(1)=2.103(3)Å). Even though the conformations and configurations of both complexes are still retained in solution, an unusual nonrigidity for the protons of the PymS region is obsered in the solution. The broad proton signals of CoⅢ(PymS)3 exhibit a temperature-dependence in the range of -40∼40℃ with a free energy of activation ΔG=64.49kJ/mol(40℃). For Cp*RhⅢ(PymS)₂,such a fluxionality has been markedly observed in solution. This fluxional behavior can be explained in terms of "ligand tautomerism" in metal complexes containing potential tautomeric forms.

• Analytical Science and Technology
• /
• v.20 no.1
• /
• pp.41-48
• /
• 2007

The determination method for the trace lead and cadmium in glass materials was developed by ICP-AES. The lead- and cadmium-DDTC chelates were formed by adding Na-DDTC (sodium diethyldithiocarbamate) as a chelating agent and extracted into MIBK (methyl-isobutyl ketone). Direct measuring of the trace lead and cadmium in glass was not possible because of the interferences of matrix elements as Na, Si, Mg and Ca of glasses unless solvent extraction of lead and cadmium was applied. This procedure was confirmed to be valid quantitative method of Pb and Cd analysis in glass did not influence of sample matrix, by applying it procedure to artifact sample and NIST SRM 1412.

• Asian-Australasian Journal of Animal Sciences
• /
• v.23 no.1
• /
• pp.90-97
• /
• 2010

An experiment was conducted to evaluate the effects of low concentrations of organic and inorganic dietary trace minerals on broiler performance and trace mineral digestibility along the small intestine of 35-day-old broiler chickens reared under floor-pen conditions. Eight hundred male, day-old Cobb broiler chickens were randomly allocated to 4 dietary treatments (25 birds per pen with 8 replicates per treatment). Broilers fed diets supplemented with 4, 20, 40 and 30 mg/kg, respectively, of Cu, Fe, Mn and Zn from organic chelates and inorganic salts achieved the same body weight gain as those supplemented at the NRC levels (8 mg Cu, 40 mg Fe, 60 mg Mn and 40 mg Zn/kg, respectively) from inorganic salts. However, birds fed a control diet without any supplementation at dietary levels of 7.4-8.8, 60.1-69.2, 14.6-15.4 and 19.1-20.6 mg/kg of Cu, Fe, Mn and Zn, respectively, had decreased feed intake and growth rate. There was no significant difference in the digestibility of Cu in all regions of the small intestine. Throughout the small intestine the apparent absorption of Mn from both organic and inorganic sources was small, whereas the digestibility of Zn seemed to be more complex, exhibiting differences in the apparent absorption due to both mineral source and intestinal site. Therefore, the digestibility of organic Zn was improved (p<0.01) in the ileum compared to inorganic Zn. The digestibility of Zn in the duodenum was smaller (p<0.05) than that in the ileum.

• Proceedings of the KSAR Conference
• /
• 2003.06a
• /
• pp.78-78
• /
• 2003

Embryonic stem (ES) cells, derived from preimplantation embryo, are able to differentiate into various types of cells consisting the whole body, or pluripotency. In contrast, terminally differentiated cells do not usually alter their nature but frequently die or transform if they are exposed to inappropriate external stimulations. In addition to the plasticity, ES cells are expected to be different from terminally differentiated cells in very many ways, such as patterns of gene expressions, ability and response of the cells in confronting environmental stimulations, metabolism, and growth rate. As a model system to differentiate these two types of cells, human ES cells (MB03) and terminally differentiated cells (HeLa), we examined the ability of these two types of cells in confronting a severe oxidative insult, that is $H_2O$$_2$. Approximately 1$\times$10$^4$ cells were plated in 96 well plate and serum starved for overnight. The conditioned cells were exposed to a various concentration of $H_2O$$_2$ fur 24 hrs and loaded with neutral red (50$\mu\textrm{g}$/ml) for 4 hrs, washed with PBS for 2 min three times, and entrapped dye was dissolved out using acetic ethanol. Cytotoxicity was determined by reading the amount of dye in the medium using microplate reader. equipped with 575 nm filter. Relative amount of the dye entrapped within MB03 or HeLa were not significantly different when cells were exposed up to 0.4 mM $H_2O$$_2$. However, this sharply decreased down to 0.12% in HeLa cells when the cells were exposed to 0.8 mM $H_2O$$_2$, while it was approximately 54% in MB03 suggesting that this concentration of $H_2O$$_2$ is the defensive threshold for HeLa cells. The resistance to oxidative stimulation reversed, however, when cells were co-treated with BSO (L-buthionine- 〔S, R〕-sulfoximine) which chelates intracellular GSH. This result suggests that cellular GSH is the major defensive mechanism of human ES cells. Induction of enzymes involved in GSH metabolism and type of cell death is currently being studied.

• Analytical Science and Technology
• /
• v.10 no.5
• /
• pp.370-377
• /
• 1997

The several fundamental parameters on the solvent extraction of Co(II), Cu(II) and Zn(II) with dithizone were investigated. The value of $K_{a1}/K_p$ of dithizone(at $25^{\circ}C$) between an aqueous phase and a chloroform was found to be $4.72{\times}10^{-11}$. And the mole ratios of metal ion to dithizone in its metal complexes were determined by mole ratio method. The extractibilities(%) for metal-dithizone chelates were obtained from the extraction equilibria of metal-dithizone complexes between an aqueous phase and a chloroform as follows. Co(II) : 92.3% at pH 8.0 : Cu(II) : 97.1% at pH 4.0 and Zn(II) : 99.0% at pH 7.0. And also, in optimum experimental conditions the extraction constants of Co(II), Cu(II) and Zn(II) were examined.

• Journal of the Korean Chemical Society
• /
• v.23 no.3
• /
• pp.141-151
• /
• 1979

The selective absorption of metal ions by chelating agent-loaded resins was studied in aqueous media. The resins were prepared by loading the conventional anion exchange resin, Dowex 1-X8 (50 to 100 mesh) with chelating agents containing sulfonic group, such as 8-hydroxy-quinoline-5-sulfonic acid (HQS) and 7-nitroso-8-hydroxyquinoline-5-sulfonic acid (NHQS). The stability of the resin was markedly influenced by the following factors; (1) the affinity and concentration of anions in the external solution, (2) the pH of the media. The optimum conditions for the absorption of metal ions were determined with respect to the pH, shaking time, and the effect of anion concentration in the medium. Under the optimum condition the order of the absorption of metal ions such as Fe(Ⅲ), Cu(Ⅱ), Pb(Ⅱ), and Zn(Ⅱ) was in accord with that of the stability constants of the chelates. The total capacities of the resins were found in the range of 0.6∼1.6 mmole metal per gram.