• Analytical Science and Technology
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• v.21 no.5
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• pp.412-423
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• 2008

A procedure based on solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry has been developed for the simultaneous analysis of 55 basic drugs in equine urine. The test scope covers diversified classes of drugs including some ${\beta}$-blockers, ${\beta}$-agonists, antihypotensives, CNS stimulants, sedatives, tranquilizers, antidepressants, antihypertensives and so on. LC-MS/MS separation and quantification was carried out in positive electrospray ionization and multiple reaction monitoring (MRM) mode. Four different brands of mixed mode cation exchange SPE sorbents; UCT XTRACT$^{(R)}$ XRDAH, Supelco DSC-MCAX$^{(R)}$, Varian Bond Elut Certify$^{(R)}$ and Waters Oasis$^{(R)}$ MCX were compared. The UCT XTRACT$^{(R)}$ XRDAH sorbent provided the best results in the preconcentration of samples, yielding relative recoveries higher than 80% except for terbutaline (41.3%), salbutamol (71.5%), heptaminol (70.7%), phenylpropanolamine (66.3%). Detection limits of the target drugs provided by the proposed analytical procedure were between 0.2~8.3 ng/mL.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.279-289
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• 2000

The objective of this study was to investigate the effect of coagulants and solid-liquid separation methods on algal removal in water treatment processes. Thus characterization of raw water quality in terms of turbidity. UV-254, $KMnO_4$ consumption, chlorophyll-a and correlation analysis of these parameters were conducted. In addition, the effect of commercial Al-based coagulants(Alum. PAC and PACS) on algal removal was studied by turbidity and organic removal, algal species removal, characteristic of pH drop and alkalinity consumption using laboratory jar tests. Organic components including UV-254, $KMnO_4$ consumption, chlorophyll-a in case of algal bloom were highly correlated with turbidity and the correlation coefficients of UV-254, $KMnO_4$ consumption, chlorophyll-a with turbidity were 0.775, 0674 and 0.623, respectively. In coagulation and sedimentation, the Al-based coagulants showed similar efficiency of organic and turbidity removal in low organic($KMnO_4$ consumption below 15mg/l) and low turbidity(below 30NTU). However, PAC and PACS showed better algal removal than alum in high organic concentration($KMnO_4$ consumption above 20mg/l) and high turbidity(above 100NTU) raw water conditions generated by high algal growth, which is considered to be due to the floc settleability. In comparison of sedimentation and flotation after chemical coagulation and flocculation, the removal efficiency of organic and turbidity were higher in case of alum dose with flotation than with sedimentation, while those were better in case or PAC and PACS with sedimentation than with flotation. Thus, Alum with flotation and PAC and PACS with sedimentation is recommended for efficient algal removal. The dominant phytoplankton in raw water were Microcystic and pediastrum simplex and the removal efficiency of algae with sedimentation using alum. PAC and PACS were 27%, 45% and 22% respectively, while those with DAF showed 100% removal of phytoplankton and zooplankton.

• Korean Journal of Environmental Agriculture
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• v.36 no.3
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• pp.201-210
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• 2017

BACKGROUND: The current study was to monitor of 9 veterinary antibiotics (ceftiofur, clopidol, florfenicol, sulfamethazine, sulfamethoxazole, sulfathiazole, tetracycline, tiamulin, and tylosin) in manure using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in positive and negative electrospray ionization mode. METHODS AND RESULTS: Sample preparation was carried out using Mcllvaine buffer and citrate salts to adjust the pH of the sample followed by purification with dispersive solid phase extraction (d-SPE). Separation of analytes during LC-MS/MS analysis was conducted using an Eclipse Plus $C_{18}$ column and the mobile phase was in gradient mode with, 0.1% formic acid and 5 mM ammonium formate in methanol (A) and 0.1% formic acid and 5 mM ammonium formate in distilled water (B). The linearity of the matrix-matched calibrations of all tested antibiotics was good, with $R^2$ determination coefficients ${\geq}0.9920$. The limit of detection (LOD) and quantifications (LOQ) were $0.1-67.0{\mu}g/kg$ and $0.4-200.0{\mu}g/kg$, respectively. Analysis of 13 solid and liquid manure samples taken from the Republic of Korea revealed concentrations less than $0.7{\mu}g/kg$ for tiamulin, $1497.6{\mu}g/kg$ for sulfamethazine. CONCLUSION: To monitor 9 veterinary antibiotics from manure samples in 13 provincial areas throughout the Republic of Korea, an analytical method was developed. The developed method was fully validated and successfully applied for monitoring various veterinary antibiotics in manure samples.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.649-653
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• 1999

A magnetic fluid separation technology was confirmed to be very effective to remove the suspended solids (SS) from aquacultural recirculating water, In this study, the effects of operating variables on the characteristics of SS removal were investigated through the test runs using magnetite of 2 $\mu$m mean diameter as magnetic powder. Magnetic flocculation here formed by adsorbing fine magnetites on the surface of suspended solid was observed. The strength of magnet was of significance in determining the SS removal efficiency as well as the capacity of the equipment. In addition, the SS removal efficiency decreased with an increase in the superficial liquid velocity, but the effect became negligible when the mass ratio of magnetite to the suspended solids was higher than 1.0.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.613-619
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• 2018

In this study, various influent sludge pre-treatment methods and the internal recirculation of thickened sludge from effluents using a liquid/solid separation unit were adopted to investigate their effects on the sludge digestion and methane production in a combined mesophilic anaerobic and thermophilic aerobic sludge digestion process. A lab-scale combined sludge digestion process was operated during 5 phases using different feed sludge pre-treatment strategies. In phase 1, the feed sludge was pre-treated with a thermal-alkaline method. In contrast, in phases 2, 3 and 4, the internal recirculation of thickened sludge from the effluent and thermal-alkaline, thermal, and alkaline pre-treatment (7 days) were applied to the combined process. In phase 5, the raw sludge without any pre-treatment was used to the combined process. With the feed sludge pre-treatment and internal recirculation, the experimental results indicated that the volatile suspended solid (VSS) removal was drastically increased from phases 1 to 4. Also, the methane production rate with the thermal-alkaline pre-treatment and internal recirculation was significantly improved, showing an increment to 285 mL/L/day in phase 2. Meanwhile, the VSS removal and methane production in phase 5 were greatly decreased when the raw sludge without any pre-treatment was applied to the combined process. Considering all together, it was concluded that the combined process with the thickened sludge recirculation and thermal-alkaline pre-treatment can be successfully employed for the highly efficient sewage sludge reduction and methane gas production.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.9
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• pp.894-899
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• 2010

We coordinated the experiments with ozone pretreatment and two-phase anaerobic digestion using solid-liquid separation to raise the efficiency of sludge volume reduction and obtained the following results. The pre-treatment with ozone reduced the solid concentration in the average of TSS $8.3{\pm}2.0%$ TSS and $9.2{\pm}}2.8%$ VSS. Of the organic material, TCOD decreased $5.1{\pm}2.4%$, but SCOD showed $72{\pm}6.5%$ increased, which was due to destruction of the cell wall and dissolution of icell media by the powerful oxidative stress of ozone. During the two-phase anaerobic digestion process, we achieved the reduction of $21.5{\pm}3.4%$ TSS, $20.2{\pm}8.4%$ VSS, $32.1{\pm}7.9%$ TCOD and $22.1{\pm}7.2%$ SCOD in average. The maximum methane gas production were 177.6 mL per g TSS, 210.8 mL per g VSS, 127.0 mL per g TCOD and 1452.0 mL per g SCOD, respectively. Solid material reduction through the two-phase anaerobic digestion and MLE (Modified Ludzack-Ettinger) processes were 93.8% of TSS and 92.0% of VSS. We concluded that suggested two-phase anaerobic digestion and MLE process could achieve the reasonable production of biogas and a maximum reduction of the sludge volume.

• Mass Spectrometry Letters
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• v.8 no.2
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• pp.39-43
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• 2017

Meldonium is a drug for treating ischemia by expanding the arteries but it can also enhance the performance of sports players. The World Anti-Doping Agency (WADA) has included it in the list of prohibited substances since 2016. Meldonium is one of the challenging substances for anti-doping testing because it is difficult to recover by general liquid-liquid or solid phase extraction due to its permanent charge and high polarity. Therefore, high-performance liquid chromatography (HPLC) is currently used by injecting a diluted urine sample (known as the "dilute-and-shoot" strategy). There is no loss of target compounds in the extraction/cleanup procedure but its high matrix effect could interfere in their separation or detection from the endogenous urinary compounds. We report a single method using high-resolution mass spectrometry that can be used for both screening and confirmation, which follows the "dilute-and-shoot" strategy. In this method, the endogenous compounds' interfering peaks in the mass spectrum are separated at a high resolution of FWHM 140,000, and the results are suitable for substance detection following the WADA guidelines. The interferences in the obtained mass spectrum of the urine matrix are identified as acetylcholine, lysine, and glutamine by further analysis and database searching. Validation of the method is performed in routine anti-doping testing, and the limit of detection is 50 ng/mL. This method uses simple sample preparation and a general reverse phase HPLC column, and it can be easily applied to other substances.

• YAKHAK HOEJI
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• v.57 no.5
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• pp.330-336
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• 2013

"The Act on Medication Treatment of Sexual Impulse of Sex Offenders" known as chemical castration has been effective since July 2011 in Korea. According to the law, monitoring of male sex hormone in urine is enforced to request National Forensic Service more than once a month after injection of medicine designed to reduce sex impulse. We established a rapid and sensitive method for the monitoring of testosterone (T) and epitestosterone (E) in human urine by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Three mL of urine was pretreated by solid-phase extraction for purification and performed enzymatic hydrolysis. The pretreated samples were extracted twice with 2 ml of ethyl acetate and n-hexane (2 : 3). The separation was applied on Thermo Hypersil GOLD C18 column ($1.9{\mu}m$, $100{\times}2.1mm$). A gradient elution of methanol and water of 0.1% formic acid were used as mobile phase and the retention time was less than 10 min. LC-MS/MS system coupled with an electrospray ionization source was performed in multiple reaction monitoring mode. The transitions of the analytes executed as following: m/z $289{\rightarrow}97$, 109 for T and E, m/z $292{\rightarrow}109$ for $T-d_3$ and $E-d_3$ as internal standards. The validation results of the method were satisfactory. The limits of detection were 0.05 ng/ml and the limits of quantification were 0.1 ng/ml. This method was successfully applied to real human urine sample. The developed method will be useful for monitoring T/E ratio in urine of sex offenders.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.86-86
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• 2012

The new approaches for silicon solar cell of new concept have been actively conducted. Especially, solar cells with wire array structured radial p-n junctions has attracted considerable attention due to the unique advantages of orthogonalizing the direction of light absorption and charge separation while allowing for improved light scattering and trapping. One-dimenstional semiconductor nano/micro structures should be fabricated for radial p-n junction solar cell. Most of silicon wire and/or pillar arrays have been fabricated by vapour-liquid-solid (VLS) growth because of its simple and cheap process. In the case of the VLS method has some weak points, that is, the incorporation of heavy metal catalysts into the growing silicon wire, the high temperature procedure. We have tried new approaches; one is electrochemical etching, the other is noble metal catalytic etching method to overcome those problems. In this talk, the silicon pillar formation will be characterized by investigating the parameters of the electrochemical etching process such as HF concentration ratio of electrolyte, current density, back contact material, temperature of the solution, and large pre-pattern size and pitch. In the noble metal catalytic etching processes, the effect of solution composition and thickness of metal catalyst on the etching rate and morphologies of silicon was investigated. Finally, radial p-n junction wire arrays were fabricated by spin on doping (phosphor), starting from chemical etched p-Si wire arrays. In/Ga eutectic metal was used for contact metal. The energy conversion efficiency of radial p-n junction solar cell is discussed.

• Journal of Wetlands Research
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• v.18 no.4
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• pp.357-362
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• 2016

Improvement of the solid-liquid separation efficiency in the secondary sedimentation tank of the biological treatment process, is known to be increasing effectiveness of the overall system operation. Sewage treatment plant effluent SS is composed of most organic substances. In order to reduce the SS component in the secondary sedimentation tank discharge, fine SS components constituting the heterogeneous should be increased by its own aggregation (self flocculation), so that can be deleted through their precipitation. So, it is improved through using the installation of double rectification wall in this secondary tank. In case, sewage is rapidly increased due to the daily change of the influent water, it was confirmed that suspended solids caused by the impact load are processed stably. Therefore, there is a need for a facility installation which can be its own aggregation for reduction suspended solids in secondary sedimentation tank.