• Journal of the Korean Chemical Society
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• v.37 no.5
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• pp.496-502
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• 1993

Spectrophotometric determination of rare earth elements with MTB and the composition ratio were investigated in the presence of surfactants of cetylpyridinium chloride (CPC), Triton X-100, dodecyltrimethylammonium bromide (DTMAB) and cetyltrimethylammonium bromide (CTMAB) at pH 6.5. The colour development between MTB and rare earths in the presence of cationic surfactants was very stable and more sensitive than that in the absence of surfactants. The largest absorbance increase was provided by CPC, which was therefore chosen for determination of rare earth elements. REE-MTB-CPC complex has absorption maxima at 650 nm and obeys the Beer's law in the range of 0∼100 ng/ml. Molar absorptivity is $6.6{\sim}9.4{\times}10^4\;mol^{-1}l\;cm^{-1}$.

• Korean Journal of Environmental Agriculture
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• v.40 no.2
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• pp.99-107
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• 2021

BACKGROUND: Pesticide uptake by a rotational crop after being used for the primary crop is a potential cause of violation against the pesticide law if the pesticide is not registered in the secondary crop. This study was conducted to investigate the plant back interval (PBI) of fluopyram for the rotational cultivation of radish. METHODS AND RESULTS: Two experimental approaches were performed the evaluation of residues in radish cultivated successively in soil 16 days after treated with fluopyram onto pepper plant (T1) and in radish cultivated in bare soil treated with fluopyram at PBI 30 and PBI 60 days (T2). A modified QuEChERS method coupled with LC/MS/MS analysis showed good linearity of matrix-matched standard calibration of fluopyram with the coefficient values of determination greater than 0.995. Recovery values at levels of 0.01, 0.05, 0.1 and 0.25 mg/kg ranged from average 84.9 to 117.6% with RSD less than 10%. Fluopyram residues in radish harvested from T1 and T2 were found as levels less than maximum residue limit. CONCLUSION: This study suggests 20~30 days as the PBI of fluopyram for the rotational cultivation of radish in the greenhouse soil treated with fluopyram used for pepper as the primary crop.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.857-863
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• 1998

A simple and new experimental method for determination of lysozyme-M. lysodeikticus cell lysis reaction and lysozyme activity was suggested using Beer's law. The UV transmittance of the solution changed with the concentration of M. lysodeikticus and the relationship between the UV transmittance and M. lysodeikticus cell concentration followed Beer's Law. In addition, it was experimentally proven that the UV transmittance of the solution was not influenced by the lysozyme concentration and product of the lysis reaction. During the lysozyme-M. lysodeikticus cell lysis reaction, thus, M. lysodeikticus cell concentration in the solution could be measured in-situ by UV-spectrophotometer. By using these experimental data, kinetic Parameters of the Michaelis-Menten equation for the lysozyme-M. lysodeikticus cell 1ysis reaction was simply determined The maximum reaction rate constant ($k_3$) and Michaelis-Menten constants were $0.1734sec^{-1}$ and $9.83{\times}10^{-6}M$ respectively. The activity of the lysozyme could also be obtained with this experiment because the lysis reaction rate of the 1ysozyme depended on its activity.

• Analytical Science and Technology
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• v.7 no.4
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• pp.455-460
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• 1994

A selective extraction-spectrophotometric method for the determination of mercury(II) with nocotinaldehyde-4-phenyl-3-thiosemicarbazone(NPS) was described. The method is based on the formation of an insoluble mercury-NPS complex, which is extratable into chloroform from an aqueous solution at pH 3.5 by shaking for 3 min. The absorbance is measured at 365nm and the molar absorptivity is $2.45{\times}10^4L\;mol^{-1}\;cm^{-1}$. The complex system conforms to Beer's law for up to $18{\mu}g\;mL^{-1}$ of mercury(II). The proposed method is simple and selective and has been satisfactorily applied to the determination of mercury in standard human hair sample.

• Elastomers and Composites
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• v.54 no.2
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• pp.156-160
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• 2019

The changes in the dispersion of carbon black in liquid polyisoprene under shear flow with time have been investigated by time-resolved ultra small-angle X-ray scattering (USAXS) method. The analyses of USAXS profile immediately after the start of shear flow clarified that the aggregates of carbon black with a mean radius of gyration of 14 nm and surface fractal dimension of 2.5 form the fractal network structure with mass-fractal dimension of 2.9. After the application of the shear flow, the scattering intensity increases with time at the observed whole entire q region, and then the a shoulder appears at $q=0.005nm^{-1}$, indicating that the agglomerate is broken and becomes smaller by shear flow. The analysis by the Unified Guinier/Power-law approach yielded several characteristic parameters, such as the sizes of aggregate and agglomerate, mass-fractal dimension of agglomerate, and surface fractal dimension of the primary particle. While the mean radius of gyration of the agglomerate decreases with time, the mean radius of gyration of the aggregate, mass fractal dimension, and surface fractal dimension don't change with time, indicating that the aggregates peel off the surface of the agglomerate.

• Water Engineering Research
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• v.3 no.4
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• pp.259-267
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• 2002

South Africa has developed a policy and law that calls and provides for the equitable and sustainable use of water resources. Sustainable resource use is dependent on effective resource protection. Rivers are the most important freshwater resources in the country, and there is a focus on developing and applying methods to quantify what rivers need in terms of flow and water quality. These quantified and descriptive objectives are then related to specified levels of ecological health in a classification system. This paper provides an overview of an integrated and systematic methodology, where, fer each river, and each river reach, the natural condition and the present ecological condition are described, and a level/class of ecosystem health is selected. The class will define long term management goals. This procedure requires each ecosystem component to be quantified, starting with the abiotic template. A modified flow regime is modelled for each ecosystem health class, and the resultant fluvial geomorphology and hydraulic habitats are described. Then the water chemistry is described, and the water quality changes that are likely to occur as a consequence of altered flows are predicted. Finally, the responses to the stress imposed on the biota (fish, invertebrates and vegetation) by modified flow and water quality are predicted. All of the predicted responses are translated into descriptive and/or quantitative management objectives. The paper concludes with the recognition of active method development, and the enormous challenge of applying the methods, implementing the law, and achieving river protection and sustainable resource-use.

• Analytical Science and Technology
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• v.7 no.3
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• pp.277-284
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• 1994

The spectrophotometric determination of rare earth elements with XO was investigated in the presence of cetylpyridium chloride(CPC), dodecyltrimethylammonium bromide(DTMAB), cetyltrimetylammonium bromide (CTMAB), Triton X-100 at pH 6.2. The complex between XO and rare earth elements in the presence of cationic surfactants was very stable and more sensitive than in the absence of surfactants. The largest absorbance increase was provided by CTMAB, which was therefore chosen for determination of rare earth elements. REE-XO-CTMAB complex has absorption maxima at 618nm and obeys the Beer's law in the range of 0~0.5 ppm. Molar absorptivity was $1.5{\times}10^5mol^{-1}cm^{-1}l$.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3615-3620
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• 2013

Two novel copper(II) bromide complexes with pyridine containing Schiff base ligands, $Cu(pmed)Br_2$ and $Cu(pmed)Br_2$ where pmed = N'-((pyridin-2-yl)methylene)ethane-1,2-diamine (pmed) and dpmed = N,N-diethyl-N'-((pyridin-2-yl)methylene)ethane-1,2-diamine (dpmed) were synthesized and characterized using X-ray single crystal structure analysis, optical and magnetic susceptibility measurements. Crystal structural analysis of $Cu(pmed)Br_2$ showed that the copper(II) ion has a distorted square-pyramidal geometry with the trigonality index of ${\tau}=0.35$ and two intermolecular hydrogen bonds, which result in the formation of two dimensional networks in the ab plane. On the other hand, $Cu(pmed)Br_2$ displayed a near square-pyramidal geometry with the value of ${\tau}=0.06$. In both compounds, the NNN Schiff base and one Br atom occupy the basal plane, whereas the fifth apical position is occupied by the other Br atom at a greater Cu-Br apical distance. The reported complexes show $g_{\mid}$ > $g_{\perp}$ > 2.0023 with a $d_{x2-y2}$ ground state and a penta-coordinated square pyramidal geometry. Variable temperature magnetic susceptibility measurements showed that the developed copper(II) complexes follow the Curie-Weiss law, that is there are no magnetic interactions between the copper(II) ions since the Cu--Cu distance is too far for magnetic contact.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.212-217
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• 1992

The thermodynamic parameters for the formation of gadolinium benzoate have been determined in the ionic medium of 0.1 M $NaClO_4$ at $25^{\circ}C$ in aqueous solution. The thermodynamic results indicate that the complex is stabilized by the excess entropy effect caused by the dehydration of reacting ions. The especially high stability of Gd(III)-benzoate compared to the monodentate ligand complexes might be ascribed to the conjugation effect of the benzene ring in the benzoate ligand. IR spectra show that benzoate anion acts as a bidentate ligand toward $Gd^{3+}$ to form a chelate ring in solid state. Magnetic susceptibility data of the compound were also obtained and well described by Curie-Weiss law in the temperature range 80${\sim}$300K.

• Applied Biological Chemistry
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• v.41 no.3
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• pp.234-239
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• 1998

In non-destructive evaluation of free acid content in apples by near- infrared spectroscopy(NIRS), browning and heat treatment of squeezed apple juice affected to the accuracy but titrable alkali concentration did not. The free acid content in apples after harvest was able to determine using different apples in harvest time for calibration making. The result of MLR, multiple correlation coefficient(R) was 0.77 and standard error of prediction(SEP) was 0.03%. The free acid content in apples during storage was able to determine using calibration equation established with stored apples, R was 0.90 and SEP was ca. 0.04%. The prediction accuracy by LAIR was not sufficient for use of quantitative analysis of free acid content in apple, but classification of law and high level in acid content was supposed to be applicable.