• Analytical Science and Technology
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• v.17 no.6
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• pp.532-535
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• 2004

A method on the determination of Co(II) after adsorbing of Co(II) on 2-mercaptobenzothiazole-loaded silica gel was studied. The conditions on the separation of Co(II) such as pH of solution, the amount of 2-mercaptobenzothiazole, the flow rate for adsorption, and the desorption solvent were optimized to 9.0, 0.05 g, $10mL\;min^{-1}$ and 1 M $HNO_3$ in ethanol, respectively. Under these optimum conditions, the calibration curve of Co(II) was obtained over concentration range of $2{\sim}120ng\;mL^{-1}$. The detection limit was $0.6ng\;mL^{-1}$. Recovery yields of Co(II) in various natural water samples were more than 90%.

• Bulletin of the Korean Chemical Society
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• v.13 no.5
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• pp.517-520
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• 1992

Solvent exchange rates of selected protons were measured by NMR saturation recovery method for yeast $tRNA^{Phe}$, at temperature from 25 to $40^{\circ}C$, in the presence of 0.1 M NaCl and various low levels of added magnesium ion. The exchange rates in zero $Mg^{2+}$ concentration indicate early melting of acceptor stem, D stem, and tertiary structure. Addition of magnesium ion stabilizes the entire D stem more effectively than any other secondary or tertiary interactions.

• YAKHAK HOEJI
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• v.24 no.2
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• pp.117-122
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• 1980

A new application of high pressure liquid chromatography for the determination of fenitrothion and cis- and trans-neopynamin in insecticidal preparations was investigated. Optimum conditions for a good separation and determination were determined; solvent system: dichloromethane + n-hexane = 17 + 83; Bow rate: 0.5ml/min; column: u-porasil ($4mm{\times}3Ocm$); absorbance wavelength: 254nm; 0.05 AUFS and sample size: 30 ul. Recovery of fenicrothion, cis- and trans-neopynamin from mixed artificial preparations was 99.6%, 99.7% and 99.8% respectively. Also reproducibility tests showed that the coefficient of variation was 0.89% for fenitrothion, 0.74% cis-neopynamin and 1.1% for trans-neopynamin. There was no interference with insecticidal preparation containing DDVP, allethrin, S-421 and kerosene. HPLC method was rapid, accurate and it gave better reproducibility and higher sensitivity than any other analytical method. It was considered that HPLC could be greatly applied to the analysis of fenitrothion and neopynamin in insecticidal preparations.

• Environmental Engineering Research
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• v.24 no.2
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• pp.191-201
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• 2019

Petroleum industry produces one of the popular hazardous waste known as Petroleum Sludge. The treatment and disposal of petroleum sludge has created a major challenge in recent years. This review provides insights into various approaches involved in the treatment, and disposal of petroleum sludge. Various methods used in the treatment and disposal of petroleum sludge such as incineration, stabilization/solidification, oxidation, and bio-degradation are explained fully and other techniques utilized in oil recovery from petroleum sludge such as solvent extraction, centrifugation, surfactant EOR, freeze/thaw, pyrolysis, microwave irradiation, electro-kinetic method, ultrasonic irradiation and froth flotation were discussed. The pros and cons of these methods were critically considered and a recommendation for economically useful alternatives to disposal of this unfriendly material was presented.

• Natural Product Sciences
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• v.28 no.3
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• pp.105-114
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• 2022

Tinospora crispa (L.) is a medicinal plant traditionally used to treat various ailments including diabetes. The stem has been widely studied for its antidiabetic properties, however the antidiabetic potential of its leaves has not been explored. This study investigates the antidiabetic properties of methanolic T. crispa stem and leaves extracts on alloxan-induced diabetic rats. The stems and leaves were extracted using Soxhlet extraction with methanol as solvent. Crude extracts were administered at 500 mg/kg body weight (BW) (high dose) and 250 mg/kg BW (low dose) via oral route to alloxan induced diabetic rats. T. crispa stem and leaves extracts was found to significantly reduce blood glucose following a twelve-week treatment period. The highest mean difference in blood glucose level was exhibited by animals in the high dose treated stem and low dose leaf extracts. Both extracts showed approximately 75% percentage recovery from hyperglycaemia. The highest regenerative capacity was observed in animals treated with the low dose leaf extract.

• International Journal of Industrial Entomology and Biomaterials
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• v.44 no.2
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• pp.29-36
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• 2022

Over the past decades, silk sericin (SS) received increasing attention in the academic and industrial fields. In nature, SS acts as a glue that holds the two strands of silk fibrils together. However, recent works suggest that SS might have a more diverse role during the silk spinning process, such as stabilizing the SF in the silk gland. On the other hand, the sericulture industry has been trying to find novel applications for SS discarded from the silk fabric manufacturing process. Recovery and refining of SS would be the first step of the recycling of SS. Using a proper solvent SS could be shaped into various forms, such as spherical beads, microparticles, fibers, and films. Moreover, the applicability of these SS materials has been investigated in various fields such as cosmetics, templates for nanomaterials, drug delivery, heavy metal adsorption, and enzyme immobilization.

• Analytical Science and Technology
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• v.28 no.6
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• pp.436-445
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• 2015

Amomi Fructus with anti-oxidative activity was chosen and essential oil was obtained by SDE (simultaneous distillation extraction), and 39 constituents were determined by GC-MS (gas chromatography-mass spectrometry). Major components were camphor, borneol acetate, borneol, D-limonene and camphene. Three solvent extracts such as hexanes, diethyl ether and methylene chloride from Amomi Fructus were obtained. These were analyzed by GC-MS and 4 more constituents were identified in addition to 39 components discovered in essential oil. Five major components such as camphor, borneol acetate, borneol, D-limonene and camphene were also detected, however the relative peak percents of those components were different from those of constituents in essential oil. To estimate the kind and the amount of materials evaporated at certain temperature and conditions from essential oil and solvent extracts, dynamic headspace apparatus was used and materials evaporated and trapped at certain conditions were analyzed by GC-MS. Recovery yield of SDE method from Amomi Fructus was measured by using camphor and standard calibration solution of camphor methanol solution and, the yield was 82.0%. Content of Hg was measured by mercury analyzer and contents of Cd, Pb, Cr, Mn, Co, Ni, Cu and Zn in Amomi Fructus, essential oils and solvent extracts were determined by ICP-MS (Inductively coupled plasma-mass spectrometer). Pb, Cd and Hg were measured in the concentration of 0.72 mg/kg, <0.10 mg/kg and 0.0023 mg/kg, respectively and these were below permission level of purity test. Contents of Mn, Cu and Zn in Amomi Fructus were 213 mg/kg, 8.29 mg/kg and 31.0 mg/kg, respectively and which were relatively higher than other metals such as Cr, Co and Ni. Metals such as Mn (0.65 ~ 9.08 mg/kg), Cu (1.16 ~ 4.40 mg/kg) and Zn (1.10 ~ 3.80 mg/kg) in essential oil and solvent extracts were detected. At this point it is not clear that the metals were cross-contaminated in the course of treating Amomi Fructus or metals were contained in Amomi Fructus. The influence evaluation toward biological model study of these metals in essential oil and solvent extracts will be needed.

• Journal of the Korean Chemical Society
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• v.37 no.5
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• pp.513-522
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• 1993

The purpose of this study is to optimize the selectivity of mobile phase solvents for separation of 25 phenols in reversed phase liquid chromatography and to accomplish the simultaneous preconcentration and separation of trace phenols from water samples. Phenols used in this study were classified into three groups, chloro-, methyl-, and nitrophenols. Quaternary solvent mobile phases were employed to improve the selectivity. Overlapping resolution maps(ORM) as a statistical simplex techniques was used to predict the optimum solvent system. Additional criterion such as pH and temperature were also investigated. In order to improve the resolution and decrease the analysis time, isoselective multisolvent gradient elution system was employed with ORM-Prism method. The simultaneous preconcentration and separation of trace phenols from water samples were performed by using XAD-2/Dowex 1-X8 tandem column. When the extraction efficiency was evaluated by sampling up to 1 L of distilled water, recovery of the phenols, except phenol, was above 90% and the limit of detection of the phenols was 5 ppb. The XAD-2/Dowex 1-X8 method was superior to C18 cartridge in terms of recovery and selectivity.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.243-250
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• 2020

The purpose of this study is to find out the possibility of applying microwave-hypochlorous acid leaching to effectively leaching Au in hydrothermal minerals on board. The comparative leaching experiment were confirmed that the leaching rate of Au with(T1)/with out(T2) of microwave nitric acid leaching. In addition, the leaching rate of Au on the conventional leaching by mechanical agitation(T3) and microwave leaching was compared. The result of microwave nitric acid leaching(solid-liquid ratio; 10%, leaching temperature; 90 ℃, leaching time; 20 min) confined that the metal leaching rate was high in the order of As>Pb>Cu>Fe>Zn, and the content of Au in the leaching residue was increased from 33.77 g/ton to 60.02 g/ton. As a result of the comparative leaching experiment using a chloride solvent, the dissolution rate of Au was high in the order of T1(61.10%)>T3(53.30%)>T2(17.30%). Therefore, chloride, which can be manufactured using seawater and that can be recycled by collecting chlorine gas generated in the leaching process, is expected to be an optimal solvent for Au leaching. In addition, the application of microwaves is believed to be effective in terms of time, efficiency and energy.

• Environmental Engineering Research
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• v.25 no.1
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• pp.88-95
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• 2020

An investigation of rare metals recovery from LiNi_xCo_yMn_zO₂ cathode material of the end-of-life lithium-ion batteries is presented. To determine the influence of reductant on the leach process, the cathode material (containing Li 7.6%, Co 20.4%, Mn 19.4%, and Ni 19.3%) was leached in H₂SO₄ solutions either with or without H₂O₂. The optimal process parameters with respect to acid concentration, addition dosage of H₂O₂, temperature, and the leaching time were found to be 2.0 M H₂SO₄, 4 vol.% H₂O₂, 70℃, and 150 min, respectively. The yield of metal values in the leach liquor was > 99%. The leach liquor was subsequently treated by precipitation techniques to recover nickel as Ni(C₄H₇N₂O₂)₂ and lithium as Li₂CO₃ with stoichiometric ratios of 2:1 and 1.2:1 of dimethylglyoxime:Ni and Na₂CO₃:Li, respectively. Cobalt was recovered by solvent extraction following a 3-stage process using Na-Cyanex 272 at pH_eq ~5.0 with an organic-to-aqueous phase ratio (O/A) of 2/3. The loaded organic phase was stripped with 2.0 M H₂SO₄ at an O/A ratio of 8/1 to yield a solution of 114 g/L CoSO₄; finally recovered CoSO₄.xH₂O by crystallization. The process economics were analyzed and found to be viable with a margin of $476 per ton of the cathode material.