• Journal of the Korean Society of Food Culture
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• v.18 no.1
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• pp.69-74
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• 2003

This study was conducted to find the appropriate fiber for extraction of volatile compounds from Perilla frutescens var. acuta. by solid phase microextraction (SPME). Two SPME fiber, carboxen/polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane (PDMS) were used to determine the selectivity of the fibers to the different flavor compounds present in the Perilla frutescens var. acuta. Thirty-nine compounds were identified in the volatile compounds extracted by CAR/PDMS fiber, including 6 aldehyde, 1 alcohol, 10 hydrocarbons, 17 terpene hydrocarbons, 2 ketones and 3 benzenes. In PDMS fiber, 3 aldehydes, 2 alcohols, 13 terpene hydrocarbons and 2 miscellaneouses were identified. Perillaldehyde was found to be major volatile flavor component of fresh Perilla frutescens var. acuta. Perillaldehyde and terpene hydrocarbons were more identified in PDMS fiber. These results suggested that the selectivity of PDMS fiber was better than that of CAR/PDMS fiber in Perilla frutescens var. acuta..

• Membrane Journal
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• v.5 no.4
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• pp.129-136
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• 1995

This study is concerned with the treatment of dye wastewater by carrier meditated emulsion liquid membrane. Optimum conditions for the removal of anionic dye and cationic dye by the emulsion liquid membrane(ELM) containing Aliquat 336 or D2EHPA were obtained in the batch operation, an actual dye wastewater was tested under these conditions. Dye reagents used were Sirius Red(Direct dye), Reactofix Supra Blue(Reactive dye), and Apollo Blue(Basic dye). The experimental variables were surfactant(Span 80) and carrier(Aliquat 336 or D2EHPA) concentration in the membrane phase, the counter ion($Na_2SO_4$) concentration in the internal phase and the amount of emulsion. Extraction equilibrium arrived within 5 minutes after starting reaction and more than 95% of dye ion could be removed. The carrier concentration in the membrane phase was the most crucial for the removal efficiency, but other variables effected to the reaction time more than the removal efficiency. The dye wastewater was treated under the optimum conditions in two steps. The absorbance at 550nm of wastewater was decreased 0.53 to below 0.03 after 10 minutes treatment.

• Analytical Science and Technology
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• v.32 no.5
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• pp.163-172
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• 2019

Methamphetamine (MA) is currently the most abused illicit drug in Korea and its major metabolite is amphetamine (AP). As MA exist as two enantiomers with the different pharmacological properties, it is necessary to determine their respective amounts in a sample. Thus a chiral stationary phase liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for identification and quantification of d-MA, l-MA, d-AP, and l-AP in human urine. Urine sample ($200{\mu}L$) was diluted with pure water and purified using solid-phase extraction (SPE) cartridge. A $5-{\mu}L$ aliquot of SPE treated sample solution was injected into LC-MS/MS system. Chiral separation was carried out on the Astec Chirobiotic V2 column with an isocratic elution for each enantiomer. Identification and quantification of enantiomeric MA and AP was performed using multiple reaction monitoring (MRM) detection mode. Linear regression with a $1/x^2$ as the weighting factor was applied to generate a calibration curve. The linear ranges were 25-1000 ng/mL for all compounds. The intra- and inter-day precisions were within 3.6 %, while the intra- and inter-day accuracies ranged from -5.4 % to 11.8 %. The limits of detection were 2.5 ng/mL (d-MA), 3.5 ng/mL (l-MA), 7.5 ng/mL (d-AP), and 7.5 ng/mL (l-AP). Method validation parameters such as selectivity, matrix effect, and stability were evaluated and met acceptance criteria. The applicability of the method was tested by the analysis of genuine forensic urine samples from drug abusers. d-MA is the most common compound found in urine and mainly used by abusers.

• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.898-907
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• 1994

The solvent extraction of an inorganic trace mercury in sea water samples was studied using zinc diethyldithiocabamate $Zn(DDC)_2$ as chelating agent. The $Zn(DDC)_2$ which maintained the stability of DDC- in the acidic aqueous solution in the course of extraction was synthesized from NaDDC and $ZnSO_4$ in this laboratory. The trace of mercury(Ⅱ) was extracted at pH 3.0 from 100 ml of sea water into 10ml of chloroform containing 0.05 M $Zn(DDC)_2$ by shaking for 5 minutes. And from the organic phase, the $Hg(DDC)_2$ was back-extracted into 10ml of 1 to 1 mixed acid of each 3% (v/v) nitric acid and hydrochloric acid by shaking for 25 minutes. The mercury back-extracted was determined by a cold vapor atomic absorption spectrophotometry. The trace mercury(Ⅱ) was so successfully extracted that this procedure could be applied to its determination in the sea water. That is, the recoveries of mercury in two kinds of samples into which as given amount of Hg(Ⅱ) was spiked were 90.0% and 93.3%, respectively.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.232-237
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• 1998

This study was carried out to find the optimal operating conditions for separation of residual uranium from the simulated radwaste solution containing 19 elements, and to evaluate the validity of the process. The selected process was based on the solvent extraction with TBP(tributyl phosphate). As an extractor, two miniature mixer-settlers with a total of 18 stages were used. Extraction yield of U, Np and Tc was about 99.2%. 32.1%, and 99.9%, respectively. The other elements were coextracted in the range of 1~4%. Extraction yield of U exceeded those of the previous work performed with batch system, which resulted in the low extractability of U (about 80%) according to the coexisting element such as Nd and Fe. It was due to the characteristics of multi-stage extractor. On the other hand, low extractability of Np was caused by various oxidation states in the nitric acid medium. In the case of Tc, its high extractability may be attributed to the complex formation with Zr and U, which is not well proved yet. All elements extracted with TBP were stripped into aqueous phase more than 99% by 0.01M $HNO_3$. From the results, this process has no problem with respect to in the same step was required, because Np was distributed in the raffinate and U product, respectively.

• Food Science and Preservation
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• v.14 no.6
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• pp.722-726
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• 2007

Extracting and analytical conditions of curcumin, and removal of bitterness substance from Curcuma longa L. were investigated. Absorption maxima was shown to be 424 nm at methanol solvent. Optimal conditions for analysis of curcumin was Zorbax eclipse $C_{18}$ column ; mobile phase, 75% MeOH ; flow rate, 0.8 mL/min ; wave length, UV 424 nm. Curcumin component was analyzed to be the highest content in methanol extract. In all samples, extraction yield by heating was shown to be effective as compared to room temperature. Curcumin contents of methanol and ethanol extracts in extraction of room temperature were 14.4 and 14.2 times higher than that of water extract, respectively. Two hot solvent extracts has a high curcumin content being 150 mg% as compared to room temperature. Extracting time was an effective condition when it was extracted for 60 minutes for elevating the curcumin content of water and methanol extracts. Bitter substance (BS) was markedly decreased in water extract by heat treatment of above $80^{\circ}C$. BS was weak in $121^{\circ}C$ treatment than in room temperature and it was however strong in $100^{\circ}C$ treatment. RT and $70^{\circ}C$ heat treatment were not different in BS intensity.

• Korean Journal of Environmental Agriculture
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• v.23 no.3
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• pp.158-169
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• 2004

For the improvement of gas chromatographic analysis of multiple pesticide residues in green pepper, lettuce and Chinese cabbage, multiresidue test mixtures (MRTMs) of 10 groups (ECD 5 groups and NPD 5 groups) and a recovery test mixture (RTM) of 18 compounds (11 compounds for ECD and 7 compounds for NPD) were established based on retention time and response to relevant detectors. A new extraction solvent (acetone: acetonitrile=1 : 9) and a clean up eluent (hexane: dichloromethane : acetonitile = 50 : 48.5 : 1.5) for solid-phase extraction (SPE) cartridge were selected to test two types of multiresidue methods (MRM I and MRM II). MRM II provided high recovery better than MRM I when RTM was tested Recovery experiment with MRTMs which was conducted using MRM II resulted in that more than seventy percents of compounds were recovered in the range of $50{\sim}140%$, while 9% of compounds were over 140% of recovery and only $7{\sim}8$ compounds failed to detect. MRM II, an improved method, could be employed for screening residues of 190 pesticides in those vegetables.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.12
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• pp.821-830
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• 2007

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction steam line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical results using the FLUENT code and the down scale experimental data on effect of geometry of the impingement baffle plate on the shell wall thinning. Additionally, a new type impingement baffle plate was installed above the impingement baffle plate in the feedwater heater and then the numerical and experimental study were performed in the same progress.

• Journal of Periodontal and Implant Science
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• v.36 no.1
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• pp.253-263
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• 2006

Purpose: Recently, dental implant systems have been widely used for the treatment of the extraction site, but we have been confronted with many limitations in esthetics, phonetics and function. Transitional implants(TI) were developed as a method of providing fixed provisional restorations during conventional implant healing. Until now, little data have been provided on korean transitional implants. The purpose of this study is to evaluate the implant placement site histologically after 4 weeks and 8 weeks. Materials and Methods : Test group( IntermetzzoTM MEGAGEN, KOREA) and control group(Mini Drive Lock, Intra Rock, U.S.A.) were immediately placed in interseptal or interproximal bone of beagle dog after mandibular premolars extraction, and had a healing period with non-submerged state but without loading, Both TI surfaces were composed of rough surfaces. Results: In the test group, the average percentage of BIC were respectively 39.40%(SD7.35) after 4 weeks and 44.05%(16.76) after 8 weeks, and In the control group were 50.75%(1.48) and 59.40%(0.00). Discussion: We evaluated the initial ability of the osseointegration of TI through this study. Because TI is placed with a conventional implant simultaneously and loaded immediately, the ability of osseointegration is a very important factor for the success of TI during the initial healing phase. Conclusion: The results of the histological evaluation of these two groups were similar to those mentioned in other studies for osseointegration of implant.

• The korean journal of orthodontics
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• v.49 no.5
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• pp.310-318
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• 2019

Objective: This study aimed to identify possible risk factors for external apical root resorption (EARR) in the maxillary incisors after orthodontic treatment. Methods: The root length of 2,173 maxillary incisors was measured on periapical radiographs of 564 patients who received orthodontic treatment. The Kappa test was performed to evaluate intraexaminer and interexaminer reproducibility. Multiple binary logistic regression was used to determine the association between EARR and various factors. Odds ratios and 95% confidence intervals were reported. Results: The risk of developing EARR was 70% higher in orthodontic treatment with maxillary premolar extraction (p = 0.004), 58% higher in patients with increased overjet (p = 0.012), 41% lower in two-phase orthodontic treatment (p = 0.037), and 33% lower in patients with deep bite (p = 0.039). The lateral incisors were 54% more likely to develop EARR (p < 0.001), dilacerated roots were 2.26 times more likely to develop EARR (p < 0.001), and for each additional millimeter of root length, the risk of EARR increased by 29% (p < 0.001). Conclusions: The potential risk factors for EARR after orthodontic treatment included treatment with maxillary premolar extraction, increased overjet at the beginning of treatment, and dilacerated roots.