• Journal of the Korean Magnetic Resonance Society
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• v.22 no.2
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• pp.34-39
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• 2018

The Nuclear Magnetic Resonance (NMR) technique using Dynamic Nuclear Polarization (DNP) procedures is one of the promising techniques that enable overcoming low sensitivity problems in NMR spectroscopy. We constructed an ODNP-NMR system using a commercial benchtop EPR spectrometer. The $^1H$ NMR peak area of water in aqueous solutions of 4-hydroxy-TEMPO was enhanced more than 95 times in the ODNP-NMR experiments. Our signal enhancement results were about 55% of the previously reported result. This could be due to non-uniform microwave power over a sample and unwanted sample heating by microwave. However, this portable ODNP-NMR spectrometer will be eventually useful for site-specific detection with nano-scale spatial resolutions and molecular dynamics studies with significantly improved signal sensitivity.

• Carbon letters
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• v.12 no.2
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• pp.85-89
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• 2011

Coloured wastewater is released as a direct result of the production of dyes as well as from various other chemical industries. Many dyes and their breakdown products may be toxic for living organisms. Activated carbon is one of the best materials for removal of dyes from aqueous solutions. The present study describes the adsorption behaviour of methylene blue dye on three microporous activated carbons, where two samples (AC-1 and AC-2) were prepared by a polymer blend technique and the other is a microporous activated carbon (ARY-3) sample from viscose rayon yarn prepared by chemical-physical activation. The effects of contact time and activated carbon dosage on decolourisation capacity have been studied. The results show that activated carbon having mixed microporosity and mesoporosity show tremendous decolourisation capacity for methylene blue. In addition, the activated carbon in the powder form prepared by the polymer blend technique shows better decolourisation capacity for methylene blue than the activated rayon yarn sample.

• Journal of environmental and Sanitary engineering
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• v.22 no.1 s.63
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• pp.29-35
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• 2007

This study was examined adsorption ability of heavy metal Hg(I), Pb(II), and U(Vl) ion use of fruit from schizandra chinensis, The fruits of schizandra chinensis sample used breaking into fragments $50{\sim}100$ mesh. The sample solution was mixed fruits of schizandra chinensis and heavy metal ion. Each heavy metal ion of into solution was quantum analysis with ICP-AES. As the result, each condition of maxium adsorption ability of heavy metal ion was high in the range of pH 5-7, adsorption time was about 15 minutes, and the optimum temperature was $100^{\circ}C$. The heavy metal ion was increased adsorption in order of increasing concentration and in ethanol solution better than in aqueous solution.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.2
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• pp.53-58
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• 2020

Free radicals including reactive oxygen species (ROS) are important chemicals in the research area of biology, pharmaceutical, medical, and environmental science as well as human health risk assessment as they are highly involved in diverse metabolism and toxicity mechanisms through chemical reactions with various components of living bodies. Electron spin resonance (ESR) spectroscopy is a powerful tool for detecting and quantifying those radicals in biological environments. In this work we observed the ESR signal of 2,2,6,6-Tetra-methyl piperidine 1-oxyl (TEMPO) in aqueous solution at various concentrations to estimate the uncertainty factors arising from the experimental conditions and signal treatment methods. As the sample position highly influences the signal intensity, dual ESR tube geometry (consists of a detachable sample tube and a position fixed external tube) was adopted. This type of measurement geometry allowed to get the relative uncertainty of signal intensity lower than 1% when triple measurements are averaged. Linear dependence of signal intensity on the TEMPO concentration, which is required for the quantification of unknown sample, could be obtained over a concentration range of ~10³ by optimizing the signal treatment method depending on the concentration range.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.584-588
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• 2008

Porous hydroxyapatite(HA) and HA-coated porous $Al_2O_3$ possessing pore characteristics required for bone substitutes were prepared by a slurry foaming method combined with gelcasting. The HA coating was deposited by heating porous $Al_2O_3$ substrates in an aqueous solution containing $Ca^{2+}$ and ${PO_4}^{3-}$ ions at $65{\sim}95^{\circ}C$ under ambient pressure. The pore characteristic, microstructure, and compressive strength were investigated and compared for the two kinds of samples. The porosity of the samples was about 81% and 80% for HA and $Al_2O_3$, respectively with a highly interconnected network of spherical pores with size ranging from 50 to $250{\mu}m$. The porous $Al_2O_3$ sample showed much higher compressive strength(25 MPa) than the porous HA sample(10 MPa). Fairly dense and uniform HA coating(about $2{\mu}m$ thick) was deposited on the porous $Al_2O_3$ sample. Since the compressive strength of cancellous bone is $2{\sim}12$ MPa, both the porous HA and HA-coated porous $Al_2O_3$ samples could be successfully utilized as scaffolds for bone repair. Especially the latter is expected suitable for load bearing bone substitutes due to its excellent strength.

• Journal of Sensor Science and Technology
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• v.20 no.1
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• pp.35-39
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• 2011

A disposable electrochemical immunosensor system has been developed for the detection of herbicide in aqueous samples. Disposable screen printed carbon electrodes(SPCE) were used as basic electrodes and an enzyme, horseradish peroxidase (HRP), and anti-herbicide antibodies was immobilised on to the working electrode of SPCE by using avidin-biotin coupling reactions. An herbicide-glucose oxidase conjugates have been used for the competitive immunoreaction with sample herbicides. The enzymatic reaction between the conjugated glucose oxidase and glucose added generates hydrogen peroxide, which was reduced by the peroxidase immobilised. The latter process caused an electrical current change, due to direct re-reduction of peroxidase by a direct electron transfer mechanism, which was measured to determine the herbicides in the sample. The optimal operational condition was found to be: $20\;{\mu}gl-1$ deglycosylated avidin loading to the working electrode and working potential +50 mV vs. Ag/AgCl. The total assay time was 15 min after sample addition. The detection limits for herbicides, atrazine and simazine, were found to be 3 ppb and 10 ppb, respectively.

• Journal of the Korean Chemical Society
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• v.21 no.5
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• pp.372-378
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• 1977

The following new techniques have been developed: (A); To a 500ml of sample water, it was adjusted pH 10 with ammonia-anmonium citrate, added 10ml of 1${\%}$ sodium diethyldithiocarbamate and extracted three times with 10ml of CHCl3. The extract was shaken with 10ml of 0.05N $HCl-4{\times}10^{-4}M\;HgCl_2$. The aqueous solution was added 2ml of 2N KCl and washed two times with 10ml of pure $CHCl_3$, and then recorded square wave polarograms. (B); To a 500ml of sample water adjusted pH 10 with ammonia-ammonium citrate, it was added 2ml of 1${\%}$ 8-hydroxyquinoline and extracted three times with 10ml $CHCl_3$. The separated $CHCl_3$ phase was shaken with 10ml of 0.2 N HCl. The aqueous solution was recorded polarograms directly. These methods can be used for determination of the ppb order of metal in water with an error of ${\pm}10{\%}$. The method (B) can not be used for the determination of zinc on account of the free 8-hydroxyquinoline.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.443-450
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• 1994

Polyelectrolytes of various ionization degrees, which are prepared by neutralization of poly(acrylic acid)(PAA), were crosslinked by ethylane glycol diglycidyl ether(EGDE) in aqueous solution. $C_{gel}$, the minimum polymer concentration at which gelation occurs, was higher than expected. $C_{gel}$ was comparable with that of neutral polymer. This is considered to be due to the size contraction of polyelectrolyte, which comes from ionic strength increase as polymer concentration is increased. $C_{gel}$ is low when molecular weight of the sample becomes high. It reveals that polyelectrolyte is crosslinked in coil form not in extended rod form. This behavior is similar to the crosslinking of neutral polymers. Polyelectrolytes of partially ionized sample generally follow the behavior of fully ionized polyelectrolyte. Polyelectrolyte with added salt was also studied. Considering the pH dependence of EDGE reactivity it was difficult to compare the system which differs in pH significantly.

• Journal of the Korean Wood Science and Technology
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• v.33 no.4 s.132
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• pp.38-44
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• 2005

This study was carried out to investigate the combustion characteristics of flame retardant treated wood by water-soluble flame retardants which are made from mixture of aqueous solution of monoammonium phosphate, sodium borate and zinc borate. The combustion characteristics for flame retardant treated wood were carried out using thermal analysis (TGA, combustion heat) and flame retardant test (LOI, flame propagation). The results of thermal analysis and flame retardant test are as follows; 1) The sample treated by F4 showed excellent flame retardant effects in almost all of combustion characteristics. 2) From TGA curves, all the samples undergo pyrolysis and oxidation in two main discrete steps. 3) The effect of flame retardant for softwood is higher than those for hardwood, and the combustion heat has decreased with increase of the content of flame retardant. 4) LOI values are almost similar in flame retardant treated wood samples. The range of LOI is from 24 to 30. However, these values are much higher than LOI value of non-treated wood sample. 5) The blended aqueous solution had a final in the range of about pH 8.4, and a slight odor of ammonia.

• Analytical Science and Technology
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• v.8 no.2
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• pp.161-166
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• 1995

Determination of acteoside in Pedicularis resupinata var. oppositifolia has been studied using ion pair liquid chromatography. Sample was extracted with 40mL methanol for 4 hrs. The extract was cleaned up by using Sep-Pak $C_{18}$ catridge and 8mL aqueous methanol eluent(methanol 50%, water 50%, phosphate buffer pH=8.0). Its determination was performed by means of IP-HPLC with a Hamilton PRP-1 polystyrene-divinylbenzene reversed phase column($15cm{\times}4.6mm$ i. d., $5{\mu}m$) and an aqueous methanol eluent(methanol 60%, water 40% phosphate buffer pH=8.2) containing of $5.0{\times}10^{-3}M$ tetrabutylammonium bromide. The established method was applied to the sample that was collected in area of Pyung Chang gun. As a result, its content ranges showed to be 0.062~0.076%.