• Archives of Pharmacal Research
• /
• v.17 no.6
• /
• pp.415-419
• /
• 1994

A simple nad rapid colorimetric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug base with bromophenol blue to give a ion-pair complex. The spectra of the complex shows a maxima at 415-420 nm with high apparent molar absorptivities. Beer's law was obeyed in the concentration range 1-8, 2-10 and $2-12{\;}{\mu}{\cdot}ml^{-1}$ for amodiaquine hydrochloride, primaquine phosphate and chloroquine phosphate respectively. The proposed method was applied to the determination of these drugs in certain formulations and the results were favourably comparable to the official methods.

• Bulletin of the Korean Chemical Society
• /
• v.12 no.5
• /
• pp.468-473
• /
• 1991

Viscoelastic properties of PET filament fibers on stress relaxation were investigated in the solvents of $H_2$O, 0.05% NaOH and 50% DMF using an Instron (UTM4-100 Tensilon) with solvent chamber. The theoretical stress relaxation equation derived by applying the Ree-Eyring's hyperbolic sine law to dashpot of three element non-Newtonian model was applied to the experimental stress relaxation curves, and the model parameters $G_1,G_2$, ${\alpha}$ and ${\beta}$ were obtained. By analyzing temperature dependency of the relaxation time, the values of activation entropy, activation enthalpy and activation free energy for flow in PET filament fiber were evaluated, the activation free energy being about 25.7 kcal/mol. The self diffusion coefficient and hole distance were obtained from parameters ${\alpha}$, ${\beta}$ and crystallite size in order to study the self diffusion and the orientation of crystallites in amorphous region and the effect of solvent.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.142.1-142.1
• /
• 2016

We present bulk diffusion rates of hydroxide ions in amorphous solid water (ASW) at 135 ~ 160 K. Previous researches showed that the diffusion mechanism of hydroxide is different from one of hydronium ions, and this implies that they have different diffusion rates. In ultra-high vacuum (UHV) chamber, low-energy scattering (LES) was used to measure ion population and temperature-programmed desorption (TPD) was conducted for measuring ASW thicknesses. To determine the diffusion rates, a simple model for $H_2O/NaOH/H_2O$ sandwich films was developed using Fick's second law. The measured surface population of hydroxide ions as a function of time was well fitted to the model, and the rates were well agreed to an Arrhenius equation.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.7
• /
• pp.549-553
• /
• 1994

The 2-(dimethylaminomethyl)thiophene (dmamt) complexes with copper(II) chloride and bromide were prepared and characterized by optical, EPR, XPS spectroscopies and magnetic susceptibility measurements. The low-energy absorption band above 850 nm and the relatively small EPR hyperfine coupling constant ($A_{//}{\simeq}$125 G) indicate the pseudotetrahedral site symmetry around copper(II) ion both in Cu(dmamt)$Cl_2$ and Cu(dmamt)$Br_2$ complexes. The higher satellite to main peak intensity of Cu $2P_{3/2}$ core electron binding energy in XPS spectra also supports the pseudotetrahedral geometry around the copper(II) ions having $CuNSX_2$ chromophores. The distortion from square-planar to pseudotetrahedral symmetry is likely to arise from the steric hindrance of the bulky dmamt ligand in the complex. Magnetic susceptibility study shows that these compounds follow Curie-Weiss law in the temperature range of 77-300 K with positive Weiss constant exhibiting the ferromagnetic interaction between copper(II) ions in solid state.

• Journal of the Korean Chemical Society
• /
• v.51 no.6
• /
• pp.569-576
• /
• 2007

In this study, the effect of grouping by communication apprehension level in paired think-aloud problem solving was examined. Three classes of 9th graders (N=99) were randomly assigned to a control group, homogeneous group or heterogeneous group based on the test scores of their communication apprehension. After the instructions concerning ‘writing balanced chemical equation', ‘the law of conservation of mass', and ‘the law of definite proportions' for 7 class hours, students' chemistry problem solving ability and the perception to the paired think-aloud problem solving were examined. Two-way ANOVA results revealed that there was an interactive effect in the score of chemistry problem solving ability test. In simple effect test for the students of low communication apprehension, the scores of the heterogeneous group were found to be significantly higher than those of the control group. However, the students in homogeneous group had relatively positive perceptions to the paired think-aloud problem solving.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.4
• /
• pp.545-548
• /
• 2004

A sensitive, selective and rapid method for the determination of nickel based on the rapid reaction of nickel(II) with QADMAA and the solid phase extraction of the Ni(II)-QADMAA chelate with $C_{18}$ membrane disks has been developed. In the presence of pH 6.0 buffer solution and sodium dodecyl sulfonate (SDS) medium, QADMAA reacts with nickel to form a violet complex of a molar ratio of 1 : 2 (nickel to QADMAA). This chelate was enriched by solid phase extraction with $C_{18}$ membrane disks. An enrichment factor of 50 was obtained by elution of the chelates form the disks with the minimal amount of isopentyl alcohol. The molar absorptivity of the chelate was $1.32{\times}10^5L\;mol^{-1}cm^{- 1}$ at 590 nm in the measured solution. Beer's law was obeyed in the range of 0.01-0.6 ${\mu}$g/mL. This method was applied to the determination of nickel in water and biological samples with good results.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.2
• /
• pp.263-266
• /
• 2004

A sensitive, selective and rapid method has been developed for the determination ${\mu}$g/L level of vanadium ion based on the rapid reaction of vanadium(V) with 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP) and the solid phase extraction of the colored chelate with $C_{18}$ cartridge. The QADEAP reacts with V(V) in the presence of citric acid-sodium hydroxide buffer solution (pH = 3.5) and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio 1 : 2 (V(V) to QADEAP). This chelate was enriched by solid phase extraction with $C_{18}$cartridge and the enrichment factor of 50 was obtained by elution of the chelates from the cartridge with ethanol. The molar absorptivity of the chelate is $1.28 {\times}10^5L\;mol^{-1}cm^{-1}$ at 590 nm in the measured solution. Beer's law is obeyed in the range of 0.01-0.6 ${\mu}$g/mL. The detection limit is 0.04 ${\mu}$g/L in the original samples. This method was applied to the determination of vanadium(V) in water and biological samples with good results.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.11
• /
• pp.3539-3543
• /
• 2012

Butacaine sulfate is an ester of p-aminobenzoic acid which has been widely used as a local anaesthetic and it is a long standing agent particularly for spinal anaesthesia. For this reason, a kinetic study of oxidation of butacaine sulfate by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB) has been carried out in $HClO_4$ medium at 303 K in order to explore this redox system mechanistic chemistry. The rate shows a first-order dependence on both $[CAB]_o$, and $[substrate]_o$, and a fractional-order dependence on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increases the rate of the reaction. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction has been found to be 1:2 and the oxidation products have been identified by spectral analysis. The observed results have been explained by plausible mechanism and the related rate law has been deduced.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.5
• /
• pp.791-794
• /
• 2007

A new azocalix[4]arene, 5,14,17,23-tetra[(2-benzoic acid)(azo)phenyl] calix[4]arene (2), has been prepared by hydrolysis of its ester derivative and characterized by 1H NMR, IR, UV-Vis spectroscopy and elemental analysis. Based on UV spectral changes, we found that 2 exhibits Pb2+ ion selectivity. In basic media, Pb2+ forms a 1:1 complex with the ligand. Beer's law is obeyed in the range of 2.0 × 10?6 ? 2.4 × 10?5 mol L?1 of Pb2+. The molar absorptivity (ε ) of 2-Pb2+ complex is 1.89 × 104 L mol?1 cm?1 at 440 nm, and the detection limit is 1.6 × 10?6 mol L?1.

• Journal of the Korean Chemical Society
• /
• v.55 no.6
• /
• pp.1042-1055
• /
• 2011

The purpose of this study was to compare the conceptual and algorithmic problem solving ability on Boyle's law and Charles's law according to cognitive levels and characteristics of students in middle school 1st grade students. For this study, questionnaire items of conceptual and algorithmic problem solving ability were developed. and the problem solving ability according to cognitive levels and characteristics of students was compared. The long-term memory effect in conceptual and algorithmic problem solving ability according to cognitive levels was investigated, and problem solving process were analyzed by questionnaire items. In the results of this study, conceptual problem solving ability was higher than algorithmic problem solving ability in all cognitive levels. There was statistically significant difference in concrete operational period and transitional period students. In comparison of the long-term memory effect in conceptual and algorithmic problem solving ability, formal operational period students had the long-term memory effect. There was no statistically significant difference in the conceptual and algorithmic problem solving ability according to private education among the characteristics of students. But there was statistically significant difference in the problem solving ability according to experiences of the scientific activities and hopes to related scientific careers. From results of analysis of problem solving process, it is known that the students had a tendency to just remember macroscopic phenomena and to solve the problems without understanding the concepts. Therefore, teaching and learning strategy is necessary to replace unscientific concepts by the scientific concepts through identifying students's unscientific concepts in advance.