• Membrane Journal
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• v.24 no.1
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• pp.1-9
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• 2014

In this study, four soluble homo- and co-polyimides using 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and 4,4'-diaminodiphenyl ether (ODA) monomers were synthesized to develop the gas separation membrane with good $CO_2/CH_4$ separation properties. To prepare the copolyimides, 20 mol% of three dianhydrides - (4,4'-(hexafluoroisoproplidene)diphthalic anhydride (6FDA), 4,4'-biphthalic anhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) - were added in DOCDA-ODA monomer mixture, respectively. All the synthesized homo- and co-polyimides were characterized by FT-IR. Their thermal properties were analyzed with differential scanning calorimeter (DSC). Dense membranes were prepared from these copolyimides to check their gas permeation properties for $CO_2$ and $CH_4$ gases using a time-lag method. The permeation testing results are as follows; DOCDA/ODA homopolymer showed 1.71 barrer of $CO_2$ permeability and 74.35 of $CO_2/CH_4$ selectivity. The three polyimide copolymers (DOCDA/6FDA-ODA, DOCDA/BPDA-ODA, DOCDA/BTDA-ODA) showed lower $CO_2/CH_4$ selectivities and higher $CO_2$ permeabilities than the homopolymer (DOCDA-ODA). DOCDA/6FDA-ODA showed twice times higher $CO_2$ permeabilities without severe $CO_2/CH_4$ selectivity loss than the DOCDA-ODA.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.665-669
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• 1994

A rapid gas chromatographic (GC) profiling method was applied to dairy products (milk and cheeses) for the simultaneous analysis of volatile and nonvolatile organic acids. Cheese samples were first made into aqueous samples by dissolving in water. The aqueous samples were then extracted with organic solvents after the acidification and NaCI saturation. The organic layers (diethyl ether : hexane= 1 : 1) were extracted with $NaHCO_3$ saturated solution with subsequent solid-phase extraction of the aqueous phases using Chromosorb P column/diethyl ether followed by triethylamine treatment. The resulting triethylammonium salts of acids were directly converted into volatile tert.-butyldimethylsilyl derivatives, which were analyzed by dual-capillary column GC, and GC-mass spectrometry. From milk and four cheese samples studied, 31 organic acids including 21 fatty acids and other hydroxy and dioic acids were tentatively identified. The amounts of the fatty acids were different among the kinds of cheese and thus the simplified retention index (RI) spectra of organic acids were useful for the visual pattern recognition of each sample, when the Direct Comparision method between cheese and a blind sample were attempted, it was quickly recognized to be a gouda cheese with the 999 ppt match quality value.

• Korean Journal of Food Science and Technology
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• v.25 no.4
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• pp.373-378
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• 1993

A rapid gas chromatographic profiling method for the simultaneous analysis of free fatty and other acids was applied to vegetable oils. Oil samples were dissolved in dichloromethane and the free acids were extracted with saturated $NaHCO_3$ solution. The aqueous extract was acidified and then loaded onto the Chromosorb P column for the extraction. The acids were eluted with diethyl ether selectively from Chromosorb P column and were treated with triethylamine to prevent the losses of volatile acids. Several long chain fatty acids were detected from soybean oil, rice-bran oil, sesame oil and perilla oil. Various organic acids including odd number fatty acids were detected in crude oil, especially sesame oil. Arachidic acid from perilla oil and vanillic acid from sesame oil, which were not reported before were detected. The content ratio of free linoleic acid to oleic acid was $1.02{\sim}1.18$, which was similar to the reported data. When the GC profile of organic acids were simplified to their corresponding retention index spectra of bar graphical forms, they presented characteristic pattern of each vegetable oil that can be quickly recognized.

• Korean Journal of Food Science and Technology
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• v.12 no.3
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• pp.185-192
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• 1980

To study lipid components of Panax ginseng produced in Korea, the lipids of fresh ginsengs were extracted with the mixture of chloroform-methanol (2:1, v/v) and those of dried ginsengs were extracted with diethyl ether respectively. The lipid components extracted were separated and quantitated by column, thin layer and gas-liquid chromatographies. The results were summarized as follows : 1. Fresh ginseng contained 0.62% total lipid of which 45.28% were neutral lipids, 18.12% glycolipids, and 36.60% phospholipids. But dried ginseng contained 0.89% total lipids of which 86.48% were neutral lipids, 9.20% glycolipids, and 4.32% phospholipids. 2. Triglycerides (37.6 to 42.5% of the total neutral lipids) and sterol esters (16.5 to 19.6%) in all the fresh and dried ginseng were the major components among the neutral lipids. Monoglycerides, diglycerides, free fatty acids and free sterols were minor components. 3. Digalactosyl diglycerides (23.5% of the total glycolipids) in the fresh ginseng and steryl liglycosides (28.9%) in the dried ginseng were predominant components among the glycopids, respectively, Esterified steryl glycosides and monogalactosyl diglycerides were also identified, and four unknown spots in the fresh ginseng and two unknown spots in the dried ginseng were present. 4. Phosphatidyl cholines (31.3 to 31.9% of the total phospholipids) and phosphatidyl glycerols (34.8 to 36.7%) in all the fresh and dried ginseng were the major components among the phospholipids. Phosphatidyl inositols and phosphatidyl ethanolamines were also identified. 5. The major fatty acids in the fresh and dried ginseng were linoleic $(62.29{\sim}64.32%)$, palmitic $(13.16{\sim}15.63%)$, oleic $(5.73{sim}7.23%)$ and linolenic $(5.73{sim}7.23%)$. The fatty acid compositions in neutral lipid fraction was similar to the pattern in those of the total lipids. But glycolipid and phospholipid fractions contained a lower percent of linoleic acid and a higher percent of palmitic acid than the neutral lipid fraction.