• 한국물환경학회지
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• 제32권6호
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• pp.649-669
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• 2016

This study explored the analytical conditions for 21 veterinary antibiotics which have been popularly sold in South Korea in 2014 but have not yet been targeted in EPA method 1694. Most of the selected antibiotics were separated by a reverse-phase C18 column with a combination of (buffered) water and organic polar solvent, which was commonly methanol and acetonitrile in the gradient elution mode. Volatile additives such as formic acid, ammonium acetate and ammonium formate were usually added to the mobile phases to minimize asymmetrical and tailing of antibiotics' peaks and to increase their ionization in mass spectrometry. The analytical methods of aminoglycoside antibiotics were distinct from those of the other antibiotics in terms of adoption of ion-pair chromatography (IPC) and hydrophilic interaction liquid chromatography (HILIC) capable of retaining and separating extremely polar compounds due to their hydrophilicity. Trifluoroacetic acid or heptafluorobutyric acid was frequently added to the mobile phase as an ion-pair reagent for the IPC. Tandem mass spectrometry was numerously applied to the detection of antibiotics using positive electrospray ionization (ESI) and the selected reaction monitoring (SRM) mode. All reviewed analytical methods had been/were validated by evaluating recovery, limits of detection and quantification, decision limit or detection capability of the methods.

• Advances in materials Research
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• 제2권1호
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• pp.15-36
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• 2013

Incorporation of polar functional moieties into polyethylene (PE) film has been achieved by graft copolymerization of polar monomers such as methacrylic acid (MAAc) and acrylamide (AAm) on to PE film, preirradiated with ${\gamma}$-rays from $^{60}Co$ source, using benzoyl peroxide (BPO) as initiator in aqueous medium. Percentage of grafting of MAAc and AAm was determined as a function of irradiation dose, monomer and initiator concentration, temperature, reaction time and amount of water. Maximum percentage of grafting of MAAc (1453%) and AAm (21.28%) was obtained at [MAAc] = $235.3{\times}10^{-2}$ mol/L, [AAm] = $23.4{\times}10^{-2}$ mol/L, [BPO] = $5.5{\times}10^{-2}$ mol/L and $16.5{\times}10^{-2}$ mol/L at $80^{\circ}C$, $90^{\circ}C$ in 180 min and 90 min respectively. The grafted PE films were characterized by FTIR, Thermogravimetric analysis (TGA) Scanning Electron Micrography (SEM) and X-ray diffraction methods. Some selective properties of grafted films such as swelling behavior, ion and metal uptake have been carried out. The biodegradation studies of the grafted PE films have also been investigated. The grafted films developed superior swelling behavior with maximum swelling (480%) in water as compared to pristine PE (13.55%), better thermal stability and ion and metal uptake studies showed promising results that can be effectively used for desalination of brackish water and separation of metals from the industrial effluents.

• Mass Spectrometry Letters
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• 제3권3호
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• pp.78-81
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• 2012

The hydrophobic hydrocarbon chain and the polar sulfate group confer surfactant properties and enable them to be used as anionic surfactants. Anionic surfactants (AS) are known for their adverse impact on environment, particularly on aquatic ecosystem. In the present study a fast, sensitive and selective method for the determination and subsequent quantification of six anionic surfactants was developed using hydrophilic interactive liquid chromatography (HILIC) coupled to a electrospray ionization (ESI) mass spectrometer (MS), in the concentration range 15-20 ${\mu}g/L$. The capability of the method was established using regression analysis and ANOVA. The method performance was evaluated by analyzing real time surface water spiked with 1-dodecyl hydrogen sulfate at 15 ${\mu}g/L$. Combined efficiency of solid phase extraction and MS detection established recovery of 89% in presence of natural matrix. These results point out that HILIC coupled to multistage MS procedures can be a powerful technique for environmental applications concerning the screening of polar contaminants.

• 지질공학
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• 제27권3호
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• pp.305-312
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• 2017

The most effective way to distinguish subsurface interfaces that produce various geophysical responses is through the integration of multiple geophysical methods, with each method detecting both a complementary and unique set of distinct physical properties relating to the subsurface. In this study, shallow seismic reflection (SSR) and ground penetrating radar (GPR) surveys were conducted at the Cheongju-Gadeok site of the Korea National Groundwater Monitoring Network to map the water table, which was measured at 12 m depth during the geophysical surveys. The water table proved to be a good target reflector in both datasets, as the abrupt transition from the overlying unsaturated weathered rock to the underlying saturated weathered rock yielded large acoustic impedance and dielectric constant contrasts. The two datasets were depth converted and integrated into a single section, with the SSR and GPR surveys conducted to ensure subsurface imaging at approximately the same wavelength. The GPR data provided detailed information on the upper ~15 m of the section, whereas the SSR data imaged structures at depths of 10-45 m. The integrated section thus captured the full depth coverage of the sandy clay, water table, weathered rock, soft rock, and hard rock structures, which correlated well with local drillcore and water table observations. Incorporation of these two geophysical datasets yielded a synthetic section that resembled a simplified aquifer model, with the best-fitting seismic velocity, dielectric constant, and porosity of the saturated weathered layer being $v_{seismic}=1000m/s$, ${\varepsilon}_r=16$, and ${\phi}=0.32$, respectively.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• Ocean and Polar Research
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• 제29권1호
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• pp.33-42
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• 2007

To obtain the overall distribution patterns and characteristics of the East Sea Intermediate Water (ESIW), the historical data obtained by the Japan Maizuru Marine Observatory (MMO) and the Korea Ocean Research and Development Institute (KORDI) were analyzed. To obtain water characteristics of the ESIW on isopycnal surfaces, temperature, salinity and dissolved oxygen were interpolated at every 0.01 interval of potential density. And then the interpolated values were averaged at the same potential density. This potential density average method preserved the salinity minimum layer more clearly compared to the depth average method. The potential density(${\sigma}_{\theta}$) range of the ESIW was $26.9{\sim}27.3$. The representative potential density of the ESIW was found to be 27.2, because the characteristics of the ESIW was clear at this density. From the horizontal distributions of physical properties on the isopycnal surface of $27.2{\sigma}_{\theta}$ it is suggested that the low salinity ESIW circulates anticlockwise over the whole basin with the high salinity intermediate water. The low salinity intermediate water extended from the northwestern part to the east along the sub-polar front and to the Ulleung Basin along the east coast of Korea.

• 공업화학
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• 제32권5호
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• pp.532-540
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• 2021

4-도데카노일옥시벤젠술폰산나트륨(sodium dodecanoyl-4-oxybenzenesulfonate; DOBS) 염은 저온에서도 효과적인 표백력과 살균력을 나타내는 물질이다. 본 연구에서는 물(W)-극성 비양자성 용매 계를 사용하는 알칼리 조건하에서 dodecanoyl chloride와 sodium 4-hydroxybenzene sulfonate로부터 DOBS의 온화하고 효율적인 합성방법을 조사하였다. 먼저 물만을 용매로 사용하고 온도 또는 시간을 변화시키며 반응한 결과, 수율은 30 ℃와 1 h 이상의 반응 조건에서 대부분 약 5% 정도로 낮게 나타났다. 효율적인 용매 계를 발견하기 위하여 극성 비양자성 용매의 종류를 변화시키며 물과 혼합하여 제조한 다양한 용매계에서 수율에 미치는 영향을 평가하였다. 수율은 아세톤(acetone; AC)과 물을 혼합한 용매 계에서 가장 우수하였으며, 온화한 반응조건(30 ℃, 1 h 및 상압)의 반응에서 약 82%의 높은 값을 나타냈다. 제조한 DOBS는 높은 표백력 및 살균력을 보여 표백활성화제로서 활용이 가능함을 확인하였다.

• Ocean and Polar Research
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• 제27권3호
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• pp.265-276
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• 2005

In order to grasp the structure and dynamics of phytoplankton communities, chlorophyll-a (Chl-a) and cell abundance were measured at 20 stations during the period from August 9 to August 21, 2003 in the southeastern Barents Sea on surface and subsurface chlorophyll maximum depth (SCM). Surface temperatures were varied from minimum $-0.7^{\circ}C(st. 18)$ to maximum $10.4^{\circ}C(st.1)$. Salinities were varied from minimum 29.9 psu(st. 18) to maximum 35.8 psu(st.2). The maximum nutrient(phosphate, nitrate, silicate) concentrations were $0.12{\mu}M,\;0.11{\mu}M,\;7.53{\mu}M$ and minimum concentrations were $0.01{\mu}M,\;0.03{\mu}M,\;1.43{\mu}M$, respectively. On SCM physical environmental factor were almost similar. Chl-a concentrations ranged from 0.23 to $2.13{\mu}g\;chi-a\;l^{-1}$ at SCM. Nano- and pico phytoplankton were the important contributors for increase of the Chl-a. It was about seven times difference between highest concentration to lowest. Phytoplankton communities were composed of diatoms, dinoflagellates, cryptophyceae, silicoflagellate, and prymnesiophyceae showing 37 taxa at surface and 38 taxa at SCM. Picophytoplankton was the most dominant in all stations and all layers, but the second groups were 2 and/or 3 taxa. Phytoplankton abundance ranged from minimum $4.3{\times}10^5\;cells\;l^{-1}$ (st. 20) to maximum $2.4{\times}10^6\;cells\;l^{\-1}$. (st. 17) at surface water. As a result, phytoplankton might be controlled by physical factors such as North Atlantic ocean currents and northern melt water among environmental factors in Barents Set h addition the dominant species were nano- and pico phytoplankton such as Phaeocystis, Cryptomonas and Dinobryon in the study area.

• 한국어류학회지
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• 제35권2호
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• pp.67-74
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• 2023

황복(Takifugu obscurus)은 양식 어종 중 하나이며, 유전체 연구에서도 의미 있는 종이다. 양식 어종의 경우 어류 마취제를 사용하면 양식 과정에 있어서 어류를 좀 더 쉽게 다룰 수 있다. 그러나, 지금까지 황복의 효과적인 마취와 회복을 위해 필요한 적절한 조건에 대한 연구는 없었다. 본 연구는 가장 일반적인 어류 마취제인 MS222를 이용하여 황복을 마취하는 데 필요한 연령, 수온 및 마취 농도 등 최적의 조건을 파악하는 데 그 목적이 있다. 실험에서는 세 가지 다른 수온(20℃, 24℃, 28℃) 및 마취 농도(125 mg/L, 150 mg/L, 175 mg/L)와 두 가지 다른 어류 연령(1년생과 2년생)을 테스트하였다. 실험 결과 황복의 적절한 마취 조건은 24℃와 28℃에서 MS-222 150 mg/L에서 175 mg/L까지의 범위였다. 2년생 어류의 경우도 28℃에서 MS-222 150 mg/L에서 175 mg/L의 범위를 보였다. 부작용과 위험을 최소화하기 위한 효과적인 마취 농도는 1년생 어류의 경우 24℃에서 MS-222 150 mg/L, 2년생 어류의 경우 28℃에서 MS-222 175 mg/L가 권장된다.

• Parasites, Hosts and Diseases
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• 제32권1호
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• pp.57-60
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• 1994

Thelohanellus kitauei 포자의 운명을 조사하기 위하여 in vitro에서 극사탈출률을 경시적으로 조사하였다. 포자를 0.45% 및 0.9%식염수, 증류수 그리고 Tyrode액에 현탁시켜 $-70^{\circ}C$에 냉동하여 장기간 보존한 바 거의 모든 포자의 활성은 최초 냉동후 1.750일 째까지 초기와 거의 같았다. 0.45% 및 0.9%식염수 그리고 증류수에 현탁시켜 $5^{\circ}C$에 보존한 포자는 각각 1,628일, 1,614일 그리고 1,721일, 항생제를 첨가한 위의 현탁액에서는 각각 1,628일, 1.614일 그리고 1,714일에 모든 포자가 사멸하였다. 한편, Tyrode액에 현탁시킨 것은 모두 235일에 모든 포자가 사멸하였다.