• Journal of the Korean Chemical Society
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• v.60 no.3
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• pp.169-176
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• 2016

In a borate buffer solution, the growth kinetics and the electronic properties of passive film on aluminum were investigated, using the potentiodynamic method, chronoamperometry, and multi-frequency electrochemical impedance spectroscopy. The corrosion of aluminum was heavily influenced by the degree of oxygen concentration because of the increasing reduction current. The oxide film formed during the passivation process of aluminum has showed the electronic properties of n-type semiconductor, which follow from the Mott-Schottky equation. It was found out that the passive film (Al(OH)₃) of Al formed in the low electrode potential changes to Al₂O₃ while the electrode potential increases. The growth kinetics data as measured by chronoamperometry suggests a mechanism in which the growth of the film of Al₂O₃ is determined by field-assisted transport of ions through the film.

• Korean Journal of Microbiology
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• v.25 no.4
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• pp.274-281
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• 1987

The effects of bovine serum albumin, myoinositol and ergosterol on protoplast formation, regeneration and fusion from auxotrophic mutants of Candida pseudotropicalis were examined. Frequency of protoplast formation ranged from 48 to 98% depending on auxotrophic types. When myoinositol (0.5mg/ml) and ergosterol (0.1mg/ml) were supplemented in the medium of cell growth, and bovine serum albumin (4mg/ml)was added to protoplasting buffer, 50-100% of cells were converted to protoplasts. Such a treatment of three additives improved 2.2-3.0 fold of regeneration rate of protoplasts. The fusion frequencies between complementary auxotrophs ranged from $7.0\times 10^{-4}$ to $1.5\times 10^{-3}$ in the optimal conditions. These values showed 1.9-2.3 fold increase when compared with fusion frequencies obtained without the treatment of additives. These results suggested that these comsion frequencies obtained without the treatment of additives. These results suggested that these xompounds may improve protoplast regeneration and fusion between complementary auxotrophs used in this study.

• Analytical Science and Technology
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• v.12 no.2
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• pp.99-104
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• 1999

A stepwise gradient elution with two wavelengths detection was performed for the separation and determination of some anions in saline water. The eight anions such as iodate, bromate, nitrite, bromide, nitrate, chromate, iodide and thiocyanate were successfully separated using AS-7 column and sodium chloride/sodium phosphate buffer solution as an eluant within 40 min. The separation behaviors of anions were studied at various sodium chloride concentrations. The peak shapes of anions of bromate, nitrite, bromide and nitrate gradually broadened as the concentration of sodium chloride increased until 1.0 M in the sample solutions. However, no effect was observed in the peak shapes of chromate, iodide and thiocynate. A good linearity was obtained at the range of ppm(mg/L). The detection limit was proved to be $10-720{\mu}g/L$ for the eight anions with $50{\mu}L$ injection volume. This method was applied to the determination of $Br^-$, ${NO_3}^-$ and $I^-$ in sea water.

• KSBB Journal
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• v.11 no.6
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• pp.676-680
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• 1996

The characteristics of controlled drug release were studied for a biodegradable drug delivery system. A biodegradable chitosan matrix was prepared after swelling chitosan with 10%-acetic acid and adding sulfadiazine. The release behavior of sulfadiazine from the chitosan matrix was studied using the Higuchi's diffusion controlled model in phosphate buffer solutions of pH 7.4 and pH 1.2. The drug release time was delayed by increasing the content of sulfadiazine. The drug release at pH 7.4 was more delayed than that at pH 1.2. The reason is that chitosan has greater swelling abilities at low pH than at high pH. The apparent release rate constant(K) increased as the concentration of drug increased. In shoat, the formulation the biodegradable chitosan matrix to suppress the burst effect of drug release mechanism, which led to a sustained release pattern.

• Korean Journal of Food Science and Technology
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• v.20 no.1
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• pp.40-44
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• 1988

This paper was carried out to investigate the relation of pH, aciidity and sourness during Kimchi fermentation and preservatives on Kimchi fermentation. Na-acetate, Na-malate, K-sorbate and K-sorbate+acetic acid were added to Kimchi samples. These Kimchi samples were fomented for 7 days at $37^{\circ}C$ and $20^{\circ}C$. In the experiment about the sourness and buffer action by organic salts which showed that the intensity of sourness was differented by the difference of pH in the same acidity. Na-acetate (0.3%) and Na-malate (0.3%) acted as good buffer, whereas K-sorbate (0.1%) and K-sorbate (0.1%)+acetic acid (0.05%) acted as lactobacilli growth enhancer in the fermentation.

• Analytical Science and Technology
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• v.12 no.6
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• pp.515-520
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• 1999

The spectrophotometric determination of Al(III) with thorin have been investigated. The optimum condition of pH, concentration of ligand and surfactant, and stability were evaluated. The thorin ligand offers selective separation of Al(III) from sample solution containing Fe(III), Ni(II), Cu(II), Pb(II) and Cu(II). Various surfactants were tested and Triton X-100 showed the best stability and the maximum absorbance in an aqueous solution of Al(III)-Thorin-Triton X-100 complex appears about 526 nm. The method was applied for the determination of Al(III) in mixed sample solution. Separation and preconcentration was performed with a short column filled with resorcinol-formaldehyde resin. Control of the pH during the column operation is essential because the adsorption capacities are very sensitive to change in pH. Their separation was carried out in 0.2 M acetic acid-sodium acetate buffer solution (pH 4.5) and 1.0 M $HNO_3$media.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1998.05a
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• pp.122-123
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• 1998

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.713-717
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• 2012

Approximately forty proteins in egg white have been widely studied for their functional properties. To develop a procedure of separation for pure and non-altered proteins from egg white, purification study was conducted to isolate lysozyme, ovotransferrin, and ovalbumin. Ion exchange cartridge can selectively separate proteins from egg white, and reversed-phase HPLC (RP-HPLC) could identify separated proteins. Proteins in egg white were purified by HI trap ion exchange cartridge SP and Q with buffers pH 8.0 and 5.2. C18 column (Phenomenex, USA) was used for RP-HPLC analysis and isocratic mobile phase was used with acetonitrile (ACN)/distilled water (DW)/trifluoroacetic acid (TFA) in the ratio of 50/50/0.1. Comparing the retention times of standards in RP-HPLC experiments showed that ovotransferrin, ovalbumin, and lysozyme in egg white were eluted successively in the RP-HPLC column after the pretreatment in SP and Q ion exchange cartridges.

• Analytical Science and Technology
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• v.23 no.1
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• pp.68-73
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• 2010

In order to develop the square wave voltammetric method determining cimetidine in an ampoule for injection, $5.00{\times}10^{-4}\;M$ cimetidine HCl solutions prepared with phosphate buffers of various pH values (3.01~8.97) were investigated by SWV. The well defined single peak due to the electrochemical reduction of -C=N-C$\equiv$N- in the structure of cimetidine moved towards the cathodic direction by -0.051V/pH as the pH values were increased indicating the involvement of hydrogen in its reduction. The calibration curves of cimetidine HCl in the concentration range between $1.00{\times}10^{-5}\;M$ and $5.00{\times}10^{-3}\;M$ prepared using three phosphate buffers yielded the slopes of 127,407nA/M (pH 3.01), 115,125nA/M (pH 5.00) and 111,287nA/M(pH 7.00) with excellent linearities of $R^2{\geqq}0.9997$. When one ampoule of Tagma Inj.$^{(R)}$ was analyzed by standard addition method by SWV, the within-day precision study (n=4) on the day of sample preparation resulted in the contents of cimetidine as $203{\pm}3.8\;mg$ (102% of the specified contents, RSD of 1.9%) and the inter-day precision (n=4) through 5 days was reasonable as 1.3% of RSD.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.131-137
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• 2011

A simple and rapid electrochemical method for the quantitative analysis of $Mn^{2+}$ ion is demonstrated with a view to examine the $Mn^{2+}$ dissolution behavior of $LiMn_2O_4$. The method described herein is based on the oxidation reaction of $Mn^{2+}$ to $Mn^{4+}(MnO_2)$ in aqueous buffer solution. Under the optimum condition (pH 8.9 0.04 M $NH_3-NH_4Cl$ buffer solution and glassy carbon working electrode), the linear range of $5{\mu}M-100{\mu}M$ (0.275-5.5 ppm) [$Mn^{2+}$] is obtained for the Linear sweep voltammetry(LSV) and $0.2{\mu}M-10{\mu}M$ (0.011-0.55 ppm) [$Mn^{2+}$] for the differential pulse voltammetry (DPV), respectively. It is also noted that the oxidation reaction of $Mn^{2+}$ ion is reduced with increasing amount of the electrolyte ($LiPF_6$, EC, EMC) added to the measuring solution, which is found to be mainly due to $LiPF_6$ and EC rather than EMC.