• The Korean Journal of Food And Nutrition
• /
• v.23 no.4
• /
• pp.556-561
• /
• 2010

Tomato fruits(Lycoperisicon esculentum) synthesize the glycoalkaloids dehydrotomatine and ${\alpha}$-tomatine, possibly as defense against bacteria, fungi and insects. We developed a new effective method to prepare and purify dehydrotomatine and ${\alpha}$-tomatine that exists in tomato fruits using alumina column chromatography and high performance liquid chromatography (HPLC). The tomato glycoalkaloids(TGA) in tomato was extracted with 2% acetic acid, and then precipitated with ammonium hydroxide(pH=10.5). The dry precipitate substance was applied on alumina column, and then fractionated with water saturated n-butylalcohol. The TGA(Fr. No. 26~36) were collected and dried under reduced pressure. The TGA was performed on a reverse phase HPLC(Inertsil ODS-2, $5\;{\mu}m$), eluted with acetonitrile/20mM $KH_2PO_4$(24:76, v/v) at 208 nm. Two peaks were detected on HPLC, and individual peak was collected by repeating HPLC. Furthermore, to confirm the identity dehydrotomatine and ${\alpha}$-tomatine, each peak isolated was hydrolyzed with 1N HCl into sugar and aglycone tomatidine. The sugars were converted to trimethylsilyl ester derivatives. The nature and molar ratios of sugars were identified by gas-liquid chromatography(GLC) and the aglycone by high-performance liquid chromatography(HPLC). The first peak (Rt=17.5 min) eluted from HPLC was identified as dehydrotomatine, and second peak(Rt=21.0 min) was as ${\alpha}$-tomatine. This technique has been used effectively to prepare and isolate dehydrotomatine and ${\alpha}$-tomatine from tomato fruits.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.04a
• /
• pp.85-88
• /
• 2011

In the trend of world wide environment preservation, researchers tried to find new environment friendly propellant instead of highly toxic propellant, Hydrazine. Among the candidates, ionic liquid propellants have lower toxicity, higher density, and higher specific impulse than Hydrazine. These ionic liquid propellants have high combustion chamber temperature, so catalyst supports such as gamma alumina cannot withstand in that temperature. Therefore, a catalyst that showed stable characteristic in high temperature is needed. Barium dopped alumina can be changed to Hexaaluminate in high temperature, and its characteristic in high temperature is superior than gamma alumina. Barium dopped Alumina is wet impregnated with Platinum and heated up to $1300^{\circ}C$ and $1400^{\circ}C$ for 2 hours. Those catalysts were examined by XRD, SEM, EDS, BET, and Drop test.

• Korean Journal of Materials Research
• /
• v.19 no.2
• /
• pp.115-118
• /
• 2009

The use of dolomite refractories has increased during the past several years in the manufacturing of clean steel during the stainless steelmaking process. However, at the same time, the use of dolomite refractories has led to what is known as the skull formation. In the present work, to understand the skull formation, the wetting characteristics of dolomite substrates by liquid Fe-19wt%Cr-10wt%Ni alloys in various oxygen partial pressures were initially investigated at 1753K using the sessile drop technique. For comparison, the wetting characteristics of alumina substrates were investigated with the same technique. It was found that the wetting index, (1+$cos{\theta}$), of dolomite is approximately 40% higher compared to those of alumina. In addition, the oxygen partial pressure to generate the surface oxide, which may capture the liquid metal on the refractory surface, for dolomite is much lower than that for alumina. From this study, it was concluded that the use of dolomite is much more closely associated with the skull formation compared to the use of alumina due to the stronger wettability and the surface oxide formation at a lower oxygen partial pressure of dolomite.

• Clean Technology
• /
• v.25 no.3
• /
• pp.256-262
• /
• 2019

Hydroxylammonium nitrate (HAN)-based liquid propellants are attracting attention as environmentally friendly propellants because they are not carcinogens and the combustion gases have little toxicity. The catalyst used to decompose the HAN-based liquid propellant in a thruster must have both low temperature activity and high heat resistance. The objective of this study is to prepare an Ru/alumina/metal foam catalyst by supporting alumina slurry on the surface of NiCrAl metal foam using a washing coating method and then to support a ruthenium precursor thereon. The decomposition activity of a HAN aqueous solution of the Ru/alumina/metal foam catalyst was evaluated. The effect of the number of repetitive coatings of alumina slurry on the physical properties of the alumina/metal foam was analyzed. As the number of alumina wash coatings increased, mesopores with a diameter of about 7 nm were well-developed, thereby increasing the surface area and pore volume. It was optimal to repeat the wash coating alumina on the metal foam 12 times to maximize the surface area and pore volume of the alumina/metal foam. Mesopores were also well developed on the surface of the Ru/alumina/metal foam catalyst. It was found that the metal form itself without the active metal and alumina can promote the decomposition reaction of the HAN aqueous solution. In the case of the Ru/alumina/metal foam-550 catalyst, the decomposition onset temperature was significantly lowered compared with that of the thermal decomposition reaction, and ${\Delta}P$ could be greatly increased in the decomposition of the HAN aqueous solution. However, when the catalyst was calcined at $1,200^{\circ}C$, the catalytic activity was lowered inevitably because the surface area and pore volume of the catalyst were drastically reduced and Ru was sintered. Further research is needed to improve the heat resistance of Ru/alumina/metal foam catalysts.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.6
• /
• pp.1628-1632
• /
• 2010

Porous ${\eta}-Al_2O_3$ was synthesized by modified sol-gel method using ionic liquid as a templating material. The addition of ionic liquid assisted to increase the surface area of alumina. However, the acidity of aluminas prepared with ionic liquids was hardly affected regardless the change of its structural properties. Among the ionic liquids used in this study, 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][$PF_6$]) was the most effective ionic liquid to produce porous ${\eta}-Al_2O_3$ particles. The catalytic performance of these aluminas has been investigated in dehydration of methanol to produce dimethyl ether. The alumina prepared with [Bmim][$PF_6$] outperformed the other aluminas except ${\eta}-Al_2O_3$ without modification in this reaction.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.6
• /
• pp.617-618
• /
• 1998

A simple and reproducible pretreatment method was developed for the determination of dioxins in milk sample. Liquid-liquid extraction (LLE) was used for the initial extraction of the analyte from milk. For the elimination of interferences coextracted from milk, acid treatment followed by multilayer silica gel, and then alumina column clean-up were performed. The clean extract could be obtained without carbon column or high performance liquid chromatographic (HPLC) clean-up procedure. Polychlorinated biphenyles (PCBs) and dioxins were separated on neutral alumina activated at 180 ℃ for 12 hours. The final extract was analyzed by HPLC and high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). The recovery of dioxins spiked in milk at 75-300 ppt level was 83.3-98.9% and their relative standard deviation was 4.1-14%.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.6
• /
• pp.619-624
• /
• 1998

A simple and reproducible pretreatment method was developed for the determination of dioxins in milk sample. Liquid-liquid extraction (LLE) was used for the initial extraction of the analyte from milk. For the elimination of interferences coextracted from milk, acid treatment followed by multilayer silica gel, and then alumina column clean-up were performed. The clean extract could be obtained without carbon column or high performance liquid chromatographic (HPLC) clean-up procedure. Polychlorinated biphenyles (PCBS) and dioxins were separated on neutral alumina activated at 180 ℃ for 12 hours. The final extract was analyzed by HPLC and high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS). The recovery of dioxins spiked in milk at 75-300 ppt level was 83.3-98.9% and their relative standard deviation was 4.1-14%.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.11
• /
• pp.3357-3361
• /
• 2013

Alumina microfibers with porous structures were prepared through hydrothermal reaction, and then used to modify the surface of carbon paste electrode (CPE). After modification with alumina microfibers, the electrochemical activity of CPE was found to be greatly improved. On the surface of alumina microfibers-modified CPE, the oxidation peak current of salvianolic acid B, a main bioactive compound in Danshen with anti-oxidative and anti-inflammatory effects, was remarkably increased compared with that on the bare CPE surface. The influences of pH value, amount of alumina microfibers and accumulation time were studied. Based on the strong signal amplification effects of alumina microfibers, a novel electrochemical method was developed for the detection of salvianolic acid B. The linear range was from 5 ${\mu}gL^{-1}$ to 0.3 mg $L^{-1}$, and the detection limit was 2 ${\mu}gL^{-1}$ (2.78 nM) after 1-min accumulation. The new method was successfully used to detect salvianolic acid B in ShuangDan oral liquid samples, and the recovery was over the range from 97.4% to 102.9%.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.6
• /
• pp.568-570
• /
• 1990

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.318-318
• /
• 2011

Etching of an ultrathin aluminum oxide film on NiAl(110) substrate by methanol is studied by home-built scanning tunneling microscopy at room-temperature. We deposited liquid methanol on thin alumina film by using a high speed solenoid valve suitable for deposition of thermally unstable molecules. It is found that only the reflection domain boundary between two domains was preferentially etched by methanol. Since the reflection domain boundary has many oxygen vacancies and irregular structures, judging from the fact, we assume that oxygen vacancies cause the chemically reactive phenomena of methanol in reflection domain boundary on an alumina film. The reactivity of the reflection domain boundary is attributed to the oxygen vacancies due to irregular structures. Similar reactivity is found on the oxygen deficient alumina produced on top of the intact alumina.