• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1764-1768
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• 2004

The present work reports on the investigations based on the interaction of sodium hydroxide with catechol derivatives. The first derivative spectra allowed the simultaneous determination of levodopa and carbidopa. The calibration graph was constructed from the first derivative signals by measuring $^1D$ at 350 nm for standard samples containing between 3 and 30 mg $L^{-1}$ of levodopa and at 305 nm for standard samples containing between 3 and 80 mg $L^{-1}$ of carbidopa. This method offers the advantages of simplicity, rapidity, selectivity and higher sensitivity than most of the existing spectophotometric methods.

• Analytical Science and Technology
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• v.7 no.4
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• pp.555-561
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• 1994

A method was described for the graphite furnace atomic absorption spectrophotometric determination of trace cadmium, copper, chromium and lead in urine samples. The elements were directly determined without any other treatments. The ash temperature was intensively optimized to improve the large background by the removal of organic materials and alkali and alkali earth metals in urine samples. Two kinds of standard solutions were used to plot calibration curves. From the recovery data, it could be confirmed that the analytical results with the synthetic urine matrix similar to real urine were more accurate than with a deionized water matrix.

• Bulletin of the Korean Chemical Society
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• v.14 no.5
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• pp.594-598
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• 1993

The protonation constants of the 14-membered tetraaza macrocycles A(3,14-dimethyl-2,6,13,17-tetraazatricyclo$[l6.4.0^{1,18}.0^{7,12}]$docosane) and B(2,3,6,13,14,17-hexamethyl-2,6,13,17-tetraazatric yclo-[l6.4.$0^{1,18}.0^{7,12}$]docosane) were measured by potentiometry. The formation constants of each of these ligands with copper(II) and nickel(II) were determined by an out-of-cell spectrophotometric method. The results indicate that the per-N-methylated macrocycle B exhibits much higher selectivity for complex formation with copper(II) over nickel(II) ion than A and other related 14-membered tetraaza macrocycles. The effects of the N-and C-substituents on the basicity and the metal ion selectivity of the ligands are discussed. The synthesis and properties of copper(II) and nickel(II) complexes of B are also described.

• Bulletin of the Korean Chemical Society
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• v.11 no.4
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• pp.303-306
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• 1990

Kinetic studies were carried out for the redox reaction of $[Co(NH_3)_4(C_2O_4)]^+$ with aqueous $[Fe(H_2O)_6]^{2+}$ solution in the present of $H^+$ by UV/VIS-spectrophotometric method. It was found that the order of $H^+$ for the reaction is first one in the higher $H^+$ concentration range of $1.67×10^{-1} M{\sim}1.00 M,$ while second order in the lower range of $6.30×10^{-2} M{\sim}1.67{\times}10^{-1} M.$ Reaction order of the substrates was found to be first order with respect to each of them. Accordingly overall reactions are third or fourth order. The results of calculation for the Extended Huckel Molecular Orbital theory contribute to estimate the preferred intermediates, bridging form of binuclear complex. On the basis of these results, we propose that this redox reaction proceed via inner-sphere reaction mechanism.

• Journal of the Korean Chemical Society
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• v.67 no.4
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• pp.217-221
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• 2023

A series of hydrophobic dodecyl-terminated 6th-generation poly(amidoamine) dendrimer (H)-encapsulated cadmium sulfide ((CdS)_n@H) nanoparticles in a co-solvent (toluene: methanol = 6.8: 3.2 v/v) are synthesized. The diameters of CdS nanoparticles within the dendrimer were estimated by analyzing the positions of the first excitonic absorption peaks of CdS in UV-vis spectra. The size of the CdS nanoparticle within the dendrimer shows a saturation value as the CdS/H ratio (n) increases, which is believed to be due to the limited physical size of the void cavity within the dendrimer. This simple and convenient method of estimating the saturation of the size of CdS in dendrimers may be useful in determining the maximum void space within other dendrimers under various solvent conditions.

• Analytical Science and Technology
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• v.36 no.1
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• pp.1-11
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• 2023

A new, sensitive, and reliable flow injection methodology was investigated for the determination of lead ion (II) in vegetables' samples using a laboratory-prepared reagent 2-[(6-methoxy-2-benzothiazoly)azo]-4-methoxy phenol (6-MBTAMP). Infrared spectroscopy, UV-visible spectrophotometry, Energy dispersive X-ray spectroscopy (EDX), Elemental Analysis (CHN), nuclear magnetic resonance spectroscopy ¹HNMR, and ¹³CNMR techniques were used to characterize the reagent and lead (II) complex. The method is based on lead ion (II) reacting with the reagent (6-MBTAMP) in a neutral solution to produce a green-red complex with a maximum absorbance at 670 nm. The optimum conditions, such as flow rate, lead ion (II) volume, reagent volume, medium pH, reagent concentration, and reaction coil length were thoroughly examined. The limits of detection (LOD) and quantification (LOQ) were determined to be 0.621 mg·L^-1 and 2.069 mg·L^-1 , respectively, while Sandell's sensitivity was determined to be 0.345 ㎍·cm^-2.

• Korean Journal of Animal Reproduction
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• v.7 no.2
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• pp.8-26
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• 1983

Various early pregnancy diagnostic methods have been developed in order to improve the reproductive efficiency in cow, mare, mule, sow, sheep, goat, dog, cat, rabbit, buffalo, camel, elephant, monkey, deer, lion, coipus and guinea pig. These methods include abdominal swelling, abdominal palpation, esturs cylce detection, Lupin test, gonadotropin assay, colostrum injection test, sperm motility assessment, cervical mucus viscosity test, Kaber chromagens method, estrogen test, A Scheim-Zond다 test, spectrophotometric detection of estrogen in urine and feces, boric acid crystraline formation test in urine, oxytocin injection test, diamino-oxidase test, PMSG HA test, behaviour test, Simolus iodine detection test, detection of tryptophane in urine, x-ray method, Cuboni and Lunaas method, vaginal biopsy method, Friedmann Schneider diagnostic method, electrode method, barium chloride detection method, ECG, Doptone method, ultrasound method, ultrasound scanning method, LDH method, rectal palpation method, CL palpation method, radioautography, serum creatine test, serum globulin test, chlormadine method, CAP method, Medata Do, pp.ers method, body fluid test, Plasma oCS detection method, ERIA, LHRH method, negative latex cogulation test and oestrone sulphate detection method. The most reliable methods with high a, pp.icability to farm animals such as sheep, mare, sow and cow are rectal palpation, ultrasound method and hormonal assay in blood and milk. However, they require complicated laboratory works for the early diagnosis of pregnancy and in most cases, the simple and economical methods which are described up to now need a long period of time after conception. Generally, it is possible to detect pregnancy after one estrus cycle, even though it varies depending on the species of animals. For improvement of the reproductive efficiency, it is required to develop a more accurate, economical, simple and early detectable method. It is anticipated that the result of a study on the detection method of EPF(early pregnancy factor) would be a, pp.icable to various animals within 6 hours after conception.

• Analytical Science and Technology
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• v.10 no.3
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• pp.209-215
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• 1997

Li-AGICs as a anode of secondary battery were synthesized by high-pressure method as a function of the Li-contents. The characteristics of these prepared compounds were determined from the studies with X-ray diffraction method, UV/VIS spectrophotometric and differential scanning calorimeter(DSC) analysis. From the results of X-ray diffraction, it was found that the lower stage intercalation compounds were formed with increase of Li-contents. The mixed stages in these compounds were also observed. In the case of the $Li_{30wt%}$-AGIC, the compounds in the stage 1 structure were formed predominantly, but the structure of only pure stage 1 for structural defect of artificial graphite is not observed. According to UV/VIS spectrophotometric analysis, $Li_{30wt%}$-AGIC shows distinguishable energy state spectrum with the position of $R(%)_{min}$ values, but the characteristic spectra of almost all Li-AGICs are not observed. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From the results, it was found that exothermic and endothermic reactions of Li-AGICs are related to thermal stability of lithium between artificial graphite layers.

• Journal of the Korean Chemical Society
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• v.38 no.5
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• pp.351-358
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• 1994

The spectrophotometric determination of trace selenium(Ⅳ) using its catalytic reaction has been studied in aqueous solutions. The catalytic reaction of phenylhydrazine hydrochloride with selenium(Ⅳ) in an acidic aqueous medium produces benzenediazonium ion which will be converted into a red-coloured azo dye by coupling with H-acid(8-amino-1-naphtol-3,6-disulfonic acid disodium salt). For the reaction, the experimental conditions such as amounts of the reagents and pH of the sample solutions were optimized. After 15 ml of the sample solution was treated with 1 ml of 0.1 M EDTA solution to mask $Fe^{3+}$, etc., 1 ml of 0.06 M phenylhydrazine hydrochloride, 1 ml of 0.02 M H-acid, and 3 ml of 0.3 M-$KClO_3$ were added into the solution, sequentially. The solution was adjusted to pH 1.4 with HCl. After it was heated in a steam bath for 30 minutes, the solution was cooled down to a room temperature and then diluted to 25 ml with deionized distilled water. A blank solution for the absorbance measurement was prepared from the deionized water. The absorbance was measured at 527 nm. Using the above procedure, the trace amount of selenium was determined in natural waters such as tap, river and pond waters by a standard curve method and recoveries of Se spiked to samples were also obtained. From the recoveries of 104 to 111%, it could be concluded that this method was applicable to the quantitative determination of ng/ml level of selenium in natural waters.

• Journal of Environmental Science International
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• v.17 no.10
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• pp.1139-1146
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• 2008

To investigate the functional properties and the antioxidant effect of pine needle(Pinus densiflora), the pine needle extract was obtained with methanol and its functionality was measured by spectrophotometric method, and the antioxidant experiment on soybean oil was carried out by the active oxygen method. The extraction yield of pine needle with 99% methanol was about 19%, the total flavonoid content of the pine needle-methanol extract was 11.32 mg/g on dry basis and the superoxide dismutase-like activity was 94.3%. The nitrite scavenging ability of the extract was pH dependent with the values of 77.44% at pH 1.2, 48.45% at pH 3.0 and 11.04% at pH 6.0, respectively. The peroxide value was 92.6 meq/kg at 5% dosage, 138.4 meq/kg at 2% dosage of the extract on 8 oxidation days. The period of the peroxide value to be 100 mg/kg was 4.9, 6.3 and 8.5 days at control, 2% and 5% dosage of extract, respectively. And the relative antioxidant effectiveness of the extract was 27.9% and 72.3% increase at 2% and 5% dosage, respectively, compared to control. The thiobarbituric acid value showed few differences within 4 oxidation days, but with the dosage of the extract it fairly decreased with considerable antioxidant effect to control above 4 days.