• Analytical Science and Technology
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• v.21 no.2
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• pp.102-108
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• 2008

Reversed-phase high performance liquid chromatography (RP-HPLC) was used for the simultaneous determination of liquiritin (LQ), glycyrrhizic acid (GA) and glabridin from licorice. An optimized run condition was selected with a binary gradient elution of methanol-water which ramped 35/65 to 80/20 (vol. %) in 0.0-8.0 min and a flow rate of 1.0 mL/min. A good linearity was obtained between 0.2 mg/mL and 1.0 mg/mL for LQ and GA, and 0.01 mg/mL-0.2 mg/mL for glabridin with the relative standard deviations less than 0.90% (n=5). The developed method was successfully applied to determination of the three components from licorice samples. The mean recoveries of three components are 80.79% for liquiritin, 89.71% for glycyrrhizic acid and 72.50% for glabridin.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.438-446
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• 1999

The optimum analytical method of aldehydes, ozone by-products, was established by reverse phase liquid chromatography. Six aldehydes including formaldehyde, acetaldehyde, acrolein, propionaldehyde, butylaldehyde and benzaldehyde, and one ketone including acetone were selected as aldehyde test samples through preliminary experiments. Such analytical conditions as the pH of citrate buffer solution, reaction temperature, reaction time, and concentration of DNPH, the component and composition of desorption solvent were optimized. As the result, pH 3.0 of citrate buffer solution, 40$^{\circ}C$ of reaction temperature, 15 minutes of reaction time, and 0.012% of DNPH concentration were chosen as optimum conditions. Aldehydes-DNPH derivatives in water were concentrated on $C_18$ Sep-Pak cartridge and followed by elution of their derivatives fraction with THF/ACN(70/30) mixture, and showed recoveries of the range from 87 to 107%. Separation condition on Nova-Pak $C_18$ column with low pressure gradient elution from ACN/MeOH/water(30/10/60) of an initial condition to 80% ACN of a final condition was found to give a good resolution within 20 minutes of run time. 86% to 103% of recovery for aldehydes using this method was similar to that for aldehyde using EPA Method 554 which is ranged from 84% to 103%.

• KSBB Journal
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• v.20 no.3
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• pp.233-237
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• 2005

In order to investigate the feasibility of 30K protein from silkworm (Bombyx mori) hemolymph (SH) on the proliferation of human cells, a simple separating procedure by anion-exchange chromatography system with Q-Sepharose fast flow gel was established. The 30K protein was eluted with an optimized condition of 0.16 M sodium chloride in 20 mM tris buffer (pH 9.0). The separated 30K protein at three concentrations of 0.04, 0.12, and 0.4 mg/ml was added to the culture medium with various human cells, such as chondrocytes, periosteum-derived cells, and MRC-5 cells, and their growth rates were measured. The cell growth rate at protein concentration of 0.4 mg/ml was always higher than that without 30K protein in all human cells tested, suggesting that the 30K protein has positive effect on the increase of the life span of human cells.

• Food Science of Animal Resources
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• v.31 no.6
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• pp.944-951
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• 2011

An improved cholesterol analysis method was developed for powdered infant formula by gas chromatographic separation after liquid-liquid extraction and partition. In the official Korea Food Standard method for cholesterol analysis, the water phase and solvent phase were not well separated in the case of emulsified foods such as powdered infant formulas and baby foods. For the rapid and simple sample preparation method, an optimized direct saponification condition was established for heating temperature, heating time, and KOH concentration. From the results, the optimum conditions were as follows: heating temperature $90^{\circ}C$, heating time 60 min, and 16 M KOH 10 mL for a 2 g infant formula sample; improved separation condition for gas chromatography was as follows: the initial oven condition was $250^{\circ}C$ for 25 min, the oven temperature was increased to $290^{\circ}C$ by $10^{\circ}C$/min ratio, and finally the oven temperature remained at $290^{\circ}C$for 9 min. The developed method could be implemented for the study of cholesterol, providing the advantages of reduced inspection time and cost in emulsified foods such as infant formula.

• Analytical Science and Technology
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• v.17 no.5
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• pp.381-387
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• 2004

To characterize chemically a spent pressurized water reactor (PWR) fuel, an analytical method for trace amounts of tritium ($^3H$) in it has been established. Considering the effective management of radioactive wastes generated through the whole experimental process and the radiological safety for analysts, a separation condition under which $^{14}C$ and $^3H$ can be sequentially recovered from a single fuel sample was optimized using simulated spent PWR fuel dissolved solutions. $^{14}CO_2$ evolved during dissolution of the spent PWR fuels with nitric acid was trapped in an aliquot of 1.5 M NaOH. $^{129}I_2$ which was volatilized along with $^{14}CO_2$ was removed using a silver nitrate-impregnated silica gel absorbent. $^3H$ remaining in the fuel dissolved solution as $^3H_2O$ was selectively recovered by distillation. Its recovery yield was 97.9% with a relative standard deviation of 0.9% (n=3). $^3H$ in a spent PWR fuel with burnup value of 37,000 MWd/MtU was analyzed, reliability of this analytical method being evaluated by standard addition method.

• Resources Recycling
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• v.27 no.5
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• pp.61-68
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• 2018

The aluminum dross is oxide generated on the surface of the molten metal during the aluminum melting process and it is divided into white dross and black dross according to presence of the Salt flux. White dross has high metal content and is recycled via the melting process. Black dross is largely berried, because the it has a low metal content and difficulty in separating the components. Black dross contains a salt components such as NaCl and KCl, and inorganic materials such as $Al_2O_3$ and MgO, and it is necessary to study the technology to recover and recycle such valuable resources. In this study, a process for recycling aluminum black dross was proposed. The inorganic and soluble substances present in the black dross were separated through crushing-dissolution-solid/liquid separation-decompression evaporating. By controlling the ratio of water and black dross, the recovery condition of the separated product was optimized and we confirmed the highest Salt flux recovery efficiency 91 wt.% at black dross:water ratio 1:9. Finally, Through the synthesis of zeolite using recovered ceramic material, the materialization possibility of black dross was confirmed.

• Analytical Science and Technology
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• v.20 no.4
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• pp.347-354
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• 2007

A simple and rapid high-performance liquid chromatography assay for the determination of residual novobiocin levels in bovine, porcine, chicken, flatfish and japanese eel muscle has been developed and validated. The separation condition for HPLC/UV was optimized with phenyl hexyl ($4.6{\times}150mm$, $5{\mu}m$) column with 10 mM monobasic sodium phosphate buffer (pH 2.5)/acetonitrile (50/50, v/v) as the mobile phase at a flow rate of 1.0 mL/min and detection wavelength was set at 254 nm. Residues were extracted from tissue by blending with methanol and lipid materials were removed with n-hexane. Then, the methanol extract was evaporated to dryness under a nitrogen stream, reconstituted in the mobile phase. Aliquot of the organic extract was decanted and filtered through $0.45{\mu}m$ syringe filter. The $20{\mu}L$ of the resulting solution was injected into the HPLC system. The calibration ranges were $0.5{\sim}5{\mu}g/g$ and calibration curves were linear with coefficients of correlation better than 0.95. The limits of quantification were $0.5{\mu}g/g$ for all muscles. The recoveries of bovine, porcine, chicken, flatfish and japaneseel muscles were 99.8%, 102.4%, 91.0%, 104.0% and 93.0%, respectively. The procedures were validated according to the CODEX guideline, determining specificity, linearity, accuracy, precision, quantitation limit and recovery.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.19-32
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• 2007

In Korea, there have been various methods of estimating groundwater recharge which generally can be subdivided into three types: baseflow separation method by means of groundwater recession curve, water budget analysis based on lumped conceptual model in watershed, and water table fluctuation method (WTF) by using the data from groundwater monitoring wells. However, groundwater recharge rate shows the spatial-temporal variability due to climatic condition, land use and hydrogeological heterogeneity, so these methods have various limits to deal with these characteristics. To overcome these limitations, we present a new method of estimating recharge based on water balance components from the SWAT-MODFLOW which is an integrated surface-ground water model. Groundwater levels in the interest area close to the stream have dynamics similar to stream flow, whereas levels further upslope respond to precipitation with a delay. As these behaviours are related to the physical process of recharge, it is needed to account for the time delay in aquifer recharge once the water exits the soil profile to represent these features. In SWAT, a single linear reservoir storage module with an exponential decay weighting function is used to compute the recharge from soil to aquifer on a given day. However, this module has some limitations expressing recharge variation when the delay time is too long and transient recharge trend does not match to the groundwater table time series, the multi-reservoir storage routing module which represents more realistic time delay through vadose zone is newly suggested in this study. In this module, the parameter related to the delay time should be optimized by checking the correlation between simulated recharge and observed groundwater levels. The final step of this procedure is to compare simulated groundwater table with observed one as well as to compare simulated watershed runoff with observed one. This method is applied to Mihocheon watershed in Korea for the purpose of testing the procedure of proper estimation of spatio-temporal groundwater recharge distribution. As the newly suggested method of estimating recharge has the advantages of effectiveness of watershed model as well as the accuracy of WTF method, the estimated daily recharge rate would be an advanced quantity reflecting the heterogeneity of hydrogeology, climatic condition, land use as well as physical behaviour of water in soil layers and aquifers.

• Korean Journal of Food Science and Technology
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• v.45 no.5
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• pp.531-536
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• 2013

We developed a simple, sensitive, and specific analytical method for prometryn using gas chromatography-mass spectrometry (GC-MS). Prometryn is a selective herbicide used for the control of annual grasses and broadleaf weeds in cotton and celery crops. On the basis of high specificity, sensitivity, and reproducibility, combined with simple analytical operation, we propose that our newly developed method is suitable for use as a Ministry of Food and Drug Safety (MFDS, Korea) official method in the routine analysis of individual pesticide residues. Further, the method is applicable in clams. The separation condition for GC-MS was optimized by using a DB-5MS capillary column ($30m{\times}0.25mm$, 0.25 ${\mu}m$) with helium as the carrier gas, at a flow rate of 0.9 mL/min. We achieved high linearity over the concentration range 0.02-0.5 mg/L (correlation coefficient, $r^2$ >0.998). Our method is specific and sensitive, and has a quantitation limit of 0.04 mg/kg. The average recovery in clams ranged from 84.0% to 98.0%. The reproducibility of measurements expressed as the coefficient of variation (CV%) ranged from 3.0% to 7.1%. Our analytical procedure showed high accuracy and acceptable sensitivity regarding the analytical requirements for prometryn in fishery products. Finally, we successfully applied our method to the determination of residue levels in fishery products, and showed that none of the analyzed samples contained detectable amounts of residues.

• Korean Journal of Food Science and Technology
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• v.44 no.3
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• pp.263-268
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• 2012

Novobiocin is a coumarin-containing antibiotic, and has a longer half-life in various animals than other veterinary medicines. A simple and rapid high-performance liquid chromatography assay for the determination of residual novobiocin levels in chicken, beef and milk has been developed and validated. The separation condition for HPLC/UVD was optimized by a MG II $C_{18}$ (4.6 mm $ID{\times}250$ mm, 5 ${\mu}m$) column with 0.1% formic acid in $H_2O$/0.1% formic acid in Acetonitrile (40/60, v/v) as the mobile phase at a flow rate of 1.0 mL/min and the detection wavelength was set at 340 nm. Residues were extracted from tissue by blending with methanol. After liquid-liquid partitioning, lipid materials were removed with n-hexane and purification as Silica (1 g, 6 mL) cartridge with 10 mL acetone/dichloromethane (10/90, v/v). Limit of quantification and linearity performed by the analytical method were 0.02 mg/kg and 0.999 ($r^2$), and the recovery range was $88.8{\pm}5.6-100.3{\pm}4.4$, $88.8{\pm}7.2-97.0{\pm}3.2$ and $88.1{\pm}4.3-92.8{\pm}3.6%$. It is expected that this analytical method with regards to novobiocin in chicken, beef and milk could be applied as an official method to administer food safety on veterinary medicines.