• Journal of the Korean Chemical Society
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• v.12 no.2
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• pp.65-80
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• 1968

The physico-chemical properties of nine selected thallium borosilicate glasses and other 21 supplementary compositions were investigated. Their composition-property curves are found to be in many respects analogous to those of other borosilicate glasses containing lithia, soda, and lead oxide. It is indicated that certain minima found in the composition-property curves of thallium borosilicate glasses might be caused by a change in boron coordination as has been observed to occur in the $Na_2O-B_2O_3-SiO_2$ glasses. Typical effects of thallium ions on the borosilicate glass are summarized as follows: 1) Addition of thallium ions increased density, refractive index, water solubility, linear coefficient of thermal expansion, and dielectric constant. 2) Increased concentration of thallium decreased the softening point of the glasses, caused fluorescence under ultraviolet radiation and smeared out the absorption edges up to $15{\mu}$ in the infrared region. An extensive liquid immiscibility was found by replication electron microscope technique in the $Tl_2O-B_2O_3-SiO_2$ system. The immiscibility covers a composition range roughly from 55 wt. % Tl2O to the binary system $B_2O_3-SiO_2.$ By acid treatment, it was found that the immiscible glass consists of separate silica-rich and boron-rich phases.

• Korean Journal of Optics and Photonics
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• v.14 no.6
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• pp.669-673
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• 2003

We fabricated a buried-ridge waveguide laser diode (B-RWG LD) which has more advantages for obtaining lateral single mode operation on the same ridge width and for the planarization of the device surface, compared to the conventional RWG LD. In this LD, the difference of the lateral effective refractive index can be controlled by the thickness of the InGaAsP layer which is grown on the active and the p-InP layers. The InGaAsP multiple quantum well was grown on a n-InP substrate by the CBE. The buried ridge structure was formed by selective wet etchings, followed by liquid phase epitaxy methods. The fabricated LD with the ridge width of 7 ${\mu}{\textrm}{m}$ showed a linear increase of the optical power up to 20 ㎽ without any kinks and a saturated output power of more than 80 ㎽. By measuring the far field pattern, we demonstrate that LDs with the ridge widths of 5 ${\mu}{\textrm}{m}$ and 7 ${\mu}{\textrm}{m}$ were operated in a lateral single mode up to 2.7I$_{th}$ and 2.4I$_{th}$, respectively.ely.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.7
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• pp.1062-1067
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• 2014

In the present study, a new analytical method was devised for the simultaneous determination of soluble carbohydrates in soybean seeds using high performance liquid chromatography/evaporative light scattering detection (HPLC/ELSD). The limit of quantification (LOQ) for soybean soluble carbohydrates ranged from 5.6~7.6 mg/kg using the HPLC/ELSD method and from 16.2~33.9 mg/kg using the high performance liquid chromatography/refractive index detection (HPLC/RID) method. Therefore, the HPLC/ELSD method was more sensitive than HPLC/RID. The precision values for retention time and peak area of the HPLC/ELSD method were evaluated by inter-day (n=5) and intra-day (n=10) assays using a standard solution. All precision values (CV<2.5%) for soybean soluble carbohydrates were acceptable and fulfilled international acceptance criteria. All linear calibration curves were obtained with a correlation coefficient of $R^2$ >0.999. The contents of soluble carbohydrates for the "Shingikong" (yellow soybean) and "Cheongjakong 3" (black soybean) samples were analyzed using the HPLC/RID and HPLC/ELSD methods. The difference in carbohydrate contents between the two detection methods was significant. Carbohydrate contents in the HPLC/ELSD method were higher than those in the HPLC/RID method. Overall, the HPLC/ELSD method showed satisfactory resolution with a favorable LOQ and reproducibility. Therefore, these results indicate that the HPLC/ELSD method may be applied to determine the contents of soluble carbohydrates in soybean seeds and related food stuffs.

• Korean Journal of Food Science and Technology
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• v.12 no.2
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• pp.115-121
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• 1980

The oils extracted with n-hexane from 6 samples of rapeseed (5 Korean samples and 1 Canadian sample) and samples of rapeseed salad oil at the market in Korea were examined. The physical and chemical characteristics of the oils were determined, and the lipid components of the oils were determined by column, thin layer-and gas liquid chromatography. The results obtained were as follows 1. The average crude fat contents in rapeseed was 43.3 % and the content of Korean was higher than that of Canadian by about 3 %. 2. The average values of specific gravity-, refractive-index, saponification value, iodine value, acid value and nonsaponifiable content of the crude oils extracted from Korean rapeseed were 0.9133, 1.4726, 103.6, 0.51 and 1.17%, respectively. 3. The average content of polar and nonpolar in total lipids were 2.7 % and 97.3 % respectively. Triglyceride was the predominant in nonpolar fraction, averaging 92.7 % of total lipids while sterol esters and diglycerides constituted 1.5 % and 1.2 % of the total. Monoglycerides, free fatty acids and free sterols were minor components of the nonpolar fraction. The polar lipids were primarily phospholipids(1.8%), but a significant amount of glycolipid (0.7%) was also found in each oil. 4. The fatty acid compositions in the total lipids showed the Korean rapeseeds averaged 46.7 % erucic, 15 % oleic, 13.4 % linoleic, 9.3 % eicosenoic and 4.3 % palmitic acids. The Canadian rapeseed, however, contained only 0.7 % of erucic acid. 5. The fatty acid compositions in nonpolar lipid fractions was similar to the pattern in those of the total lipids. But phospholipid and glycolipid fractions were lower in erucic acid content than nonpolar lipid fractions.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.109-121
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• 1992

For the purpose of mineralogical and chemical study on the topazes from various localities of world(Brzail, China, India, Nigeria and Sri Lanka), electron microprobe analysis(EPMA), neutron activation analysis(NAA), X-ray diffractometry, Raman spectroscopy, etch test, scanning electron microscopy, refractive index, specific gravity, fluid inclusion were performed. The chemical composition in topaz was discussed along with its physical and structural properties. Variations in the unit-cell dimension and physical properties of topaz were found to have a close relations in the unit-cell dimension and physical properties of topaz were found to have a close relationship with extent of substitution of $OH^-\;for\;F^-$. According to neutron activation analyses, the trace elements had no effects on the physical properties of topaz. Raman spectra showed that the peaks of topaz were different in intensity from one locality to another. Etching defects in topaz includes negative crystal defect o point-bottom pit(India, Nigeria) and net work defect of curl-bottom pit(Brazil, China). Fluid inclusions in topaz may be classiffied into liquid $CO_2$-bearing inclusion, gaseous inclusion, halite, sylvite-bearing inclusion and liquid inclusion. The results of this study can be useful to devising artificial coloring methods for topaz with different mineralogical compositions.

• Journal of Dairy Science and Biotechnology
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• v.33 no.4
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• pp.263-269
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• 2015

Various carbohydrates (lactose, glucose, and fructose), lactic acid, uric acid, and acetoin were separated on a ZORBAX Carbohydrate Analysis column using the Agilent 1200 HPLC ChemStation$^{TM}$, and were identified according to retention times with 325 Dual Wavelength UV-Vis Detector and Refractive Index Detector with 0.013 N $H_2SO_4$ at a flow rate of 0.8 mL/min. In addition, the lactase activity of four commercial probiotic lactic acid bacteria during 6-hour incubation was determined using a high-performance liquid chromatography (HPLC) method. Among the tested samples, Bifidobacterium animalis subsp. lactis showed the greatest lactase activity, followed by Lactobacillus rhamnosus and Lactobacillus casei, with Streptococcus salivarius subsp. thermophilus showing the lowest activity. Therefore, this HPLC technique shows potential for evaluating the fermentation processes of probiotic lactic acid bacteria and could simultaneously confirm the degree of ripening in various fermented dairy foods within only a half hour.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.11
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• pp.1666-1671
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• 2015

The purpose of this study was to provide trustworthy nutritional information by analyzing sugar contents of commercial retort foods. A total of 70 retort food samples were collected, which included curry (n=21), blackbean- sauce (n=16), sauce (n=17), and meat (n=16) from markets in Seoul and Gyeonggi-do. Contents of sugars such as glucose, fructose, sucrose, maltose, and lactose were analyzed in retort foods by using a high performance liquid chromatography-refractive index detector and compared to their assigned values on nutritional information labels. Analyzed sugar contents of curries, black-bean-sauces, sauces, and meats ranged from 1.05~4.63 g/100 g, 1.76~5.16 g/100 g, 0.35~25.44 g/100 g, and 1.98~11.07 g/100 g, respectively. Sauces were found to contain the highest amounts of total sugar. These analysis values were equivalent to the reference values indicated on nutrition labels, which were 40~119.5% for curries, 29~118% for black-bean-sauces, 18~118% for sauces, and 70~119.8% for meats. Therefore, this study provides reliable analytical values for sugar contents in retort foods.

• Korean Journal of Food Science and Technology
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• v.43 no.1
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• pp.58-64
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• 2011

The purpose of this study was to analyze the content and consumption of total sugar from school lunches at Incheon and Chuncheon. The samples were collected from eight elementary schools and eight middle schools in Incheon and Chuncheon for 15 days. The analysis of total sugar content was performed for 1334 main dishes, side dishes, and desserts, which were supplied by elementary and middle school foodservices. Total sugar content was extracted from various types of food with 50% ethanol after defatting. We simultaneously analyzed sugars such as fructose, glucose, sucrose, maltose, and lactose by a high performance liquid chromatography with refractive index detector. The average lunch intake for elementary school and middle school students was $372.6{\pm}72.2g$ and $449.2{\pm}81.1g$, respectively. The total sugar content in desserts was $7.21{\pm}6.32g/100g$, $1.69{\pm}2.44g/100g$ in side dishes, and $0.32{\pm}0.77g/100g$ in main dishes. Among side dishes, fried foods, stir-fried foods, and sauces contained the highest amounts of total sugar. The total sugar intake was $4.63{\pm}5.11g$ in desserts, $0.64{\pm}1.01g$ in side dishes, and $0.55{\pm}1.48g$ in main dishes. Main and side dishes with a high total sugar intake included cooked rice with seasoning, fried foods, stir-fried foods, and preserved foods. The average total sugar intake per meal for elementary school, middle school, and all students was $4.03{\pm}3.67g$, $6.97{\pm}6.59g$, and $5.50{\pm}5.53g$, respectively. We have provided useful information to decrease the intake of total sugar in school lunches. It is recommended that total sugar intake be continuously monitored.

• Korean Journal of Food Science and Technology
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• v.36 no.1
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• pp.14-18
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• 2004

Analysis methods of artificial sweeteners, aspartame, acesulfame potassium, sodium saccharin, and sucralose isolated from foods were developed using high performance liquid chromatography, HPLC conditions for aspartame, acesulfame potassium, and sodium saccharin were: column, Symmetry $C_{18}(3.9mm\;i.d{\times}150mm,\;5{\mu}m)$; mobile phase, 0.05M sodium phosphate monobasic : acetonitrile (9 : 1, pH 3.5, containing 0.01M tetrapropylammonium hydroxide); detector, UV detector at 210 nm. HPLC condition for sucralose were : column, Symmetry $C_{18}(3.9mm\;i.d{\times}150mm,\;5{\mu}m)$; mobile phase, water:methanol (7 : 3); detector, refractive index detection (sensitivity = 16). Recoveries of artificial sweeteners in foods including soft drinks, fruit and vegetable beverages, alcoholic beverages, fermented milk beverages, soybean milk, ice cream, snacks, chewing gums, jam, honey, kimchi salted food, special dietary products, processed fish products, candies, food additive mixtures, chocolate and cocoa were 76.1-101.3%, 82.3-103.2%, 83.1-103.7%, and 80,6-99.5% for aspartame, acesulfame potassium, sodium saccharin, and sucralose, respectively.