• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.1
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• pp.174-179
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• 2000

The nitrogenous compounds in the muscle extracts of cultured and wild olive flounder, Paralichthys olivaceous, were analyzed. The analyzed coumpounds were extractive nitrogen, free amino acids, oligopeptides, ATP and its related ompounds, quaternary ammonium bases, and guanidino compounds. The distribution pattern of these compounds in cultured and wild fish was found to be very similar. Although the ATP and its related compounds and creatine in the muscle of cultured fish were slightly abundant than those in the muscle of wild one, the extractive nitrogen, total free amino acid, oligopeptides, and TMAO were found to be slightly rich in the muscle of wild fish than those in the muscle of cultrued one. The moisture content of cultured fish was relatively lower but the protein and fat contents of cultured one were higher than those of wild fish. However the differences in the proximate composition, extractive nitrogen and nitrogenous compounds between two fishes were not significantly different.

• Analytical Science and Technology
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• v.28 no.3
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• pp.228-235
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• 2015

The efficiency and applicability of the solid phase extraction disk method in a ²²⁶Ra analysis were examined by the gamma ray spectrometer (GRS) method using a Marinelli beaker and the liquid scintillation counter (LSC) method for groundwater. The recovered ²²⁶Ra, which was filtered by the solid phase extraction disk, was analyzed using gamma ray spectrometer The disks, which were pretreated for caulking the daughter nuclide, were sealed with polyethylene film. Distilled water was used for the blank value of the ²²⁶Ra activity. The recovery values of ²¹⁴Bi and ²¹⁴Pb in the solid phase extraction disk, which used ²²⁶Ra standard material, were 80% (295.21 Kev) and 104% (351.92 Kev), respectively, which were higher than 75% determined by the LSC. The injection of nitrogen gas into the measuring chamber reduced the interference values by about 10%. The detection limits of the ²²⁶Ra activity in a blank sample of 5 L were 0.17~0.40 pCi/L after 80,000 seconds of measuring time. The relationship of the ²²⁶Ra activity in the solid phase extraction disk method and in the LSC method in seven groundwater samples showed a correlation coefficient value 0.987, which implies the applicability of the solid phase extraction disk method. The results showed that ²²⁶Ra activity in groundwater using the solid phase extraction disk method has the following benefits: simple pretreatment, time saving, high recovery values, a low detection limit, and so on. Compared with the LSC method and the GRS method using the Marinelli beaker for the ²²⁶Ra analysis, the solid phase extraction disk method could be useful in groundwater samples with low levels of activities of radionuclides because the method is not restricted by the volume of the sample.

• Korean Journal of Food Science and Technology
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• v.42 no.3
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• pp.257-262
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• 2010

Patulin, a secondary metabolite of mold, is commonly found in rotten apples. Many countries regulate patulin at levels ranging from 30 to $50\;{\mu}g/L$. Most analytical methods for removing patulin from apple juice include liquid-liquid extraction (LLE), which is time and labor intensive. To replace the LLE method, a solid-phase extraction (SPE) method has been developed for apple juice and unfiltered apple juice. A portion of the test sample was applied to a macroporous copolymer cartridge and washed with 5 mL of 1% sodium bicarbonate, followed by 5 mL of 1% acetic acid. Patulin was eluted with 5 mL of 2% acetonitrile in anhydrous ethyl ether. The mobile phase was tetrahydrofuran in water (0.8:99.2) and was detected with a UV detector at 276 nm. Recoveries ranged from 95 to 101% in test samples, and the minimum detectable level was 30 ppb. Because this SPE method is fast, easy, reliable, and inexpensive, it could be applicable for companies or analytical agencies to analyze patulin concentrations in apple juice.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.361-370
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• 2010

Considering the efficiencies of the preparation process at each stage obtained in previous studies, the analytical determination method was established for multi-pesticide residues in soils. It consist of the acetone-extraction, the dichloromethane-partition, the Florisil or silica-gel chromatography and the gas chromatography analysis equipped with the electron capture detector and the nitrogen-phosphorus detector. In the soil recovery test by Florisil clean-up system, the number of pesticides recovered in the range of 70~120% and showed less than 20% of RSD were 165 pesticides for paddy soil, 169 pesticides for upland soil and 159 pesticides in both soils through the tested 183 pesticides. And in the soil recovery test by silica-gel system, the number of pesticides recovered in the range of 70~120% and showed less than 20% of RSD were 154 pesticides for paddy soil, 145 pesticides for upland soil, and 134 pesticides in both soils.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.3
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• pp.173-178
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• 2003

To determine the optimum $\textrm{P}_2\textrm{O}_5$ rate for dry matter production of Achyranthes japonica Nakai a medicinal plant, in Jeju island, plants were grown in 2001 under ten fertilizer treatments comprising of two N (90, and 180kg/ha) and five $\textrm{P}_2\textrm{O}_5$ (0, 100, 200, 300, and 400 kg/ha) levels. Plant height leaf length and width, stem diameter, and main root length and diameter were not significantly affected by $\textrm{P}_2\textrm{O}_5$ rate while $\textrm{P}_2\textrm{O}_5$ fertilization of 100 kg/ha increased the number of branches, spikes, and roots per hill by 18,38 and 43%, respectively, compared with the unfertilized $\textrm{P}_2\textrm{O}_5$ treatment and decreased with further increases in $\textrm{P}_2\textrm{O}_5$ rate. The number of roots per hill was greatest with the application of 200kg $\textrm{P}_2\textrm{O}_5$. The highest utricle dry matter yield (2.92 t/ha) was obtained with the application of 100kg $\textrm{P}_2\textrm{O}_5$. However, as $\textrm{P}_2\textrm{O}_5$ rate increased from 0 to 100 and 200kg/ha, root dry matter yield increased from 2.36 to 3.55, and 3.80 t/ha, and then decreased to 3.14, and 2.86 t/ha at 300, and 400kg $\textrm{P}_2\textrm{O}_5$ rates, respectively. As $\textrm{P}_2\textrm{O}_5$ rate increased from 100 to 400 kg/ha, $\textrm{P}_2\textrm{O}_5$ recovery in aboveground parts decreased from 34.1 to 7.1%.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.11
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• pp.764-770
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• 2014

This study assessed analysis of N-nitrosamines by separation, identification, and quantification using a gas chromatography (GC) mass spectrometer (MS) with electron impact (EI) mode. Samples were pretreated by a automated solid phase extraction (SPE) and a nitrogen concentration technique to detect low concentration ranges. The analysis results by EI-GC/MS (SIM) and EI-GC/MS/MS (MRM) on standard samples with no pretreatment exhibited similar results. On the other hand, the analysis of pretreated samples at low concentrations (i.e. ng/L levels) were not reliable with a EI-GC/MS due to the interferences from impurity peaks. The method detection limits of eight (8) N-nitrosamines by EI-GC/MS/MS analysis ranged from 0.76 to 2.09 ng/L, and the limits of quantification ranged from 2.41 to 6.65 ng/L. The precision and accuracy of the method were evaluated using spiked samples at concentrations of 10, 20 and 100 ng/L. The precision were 1.2~13.6%, and the accuracy were 80.4~121.8%. The $R^2$ of the calibration curves were greater than 0.999. The recovery rates for various environmental samples were evaluated with a surrogate material (NDPA-$d_{14}$) and ranged 86.2~122.3%. Thus, this method can be used to determine low (ng/L) levels of N-nitrosamines in water samples.

• Analytical Science and Technology
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• v.20 no.4
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• pp.347-354
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• 2007

A simple and rapid high-performance liquid chromatography assay for the determination of residual novobiocin levels in bovine, porcine, chicken, flatfish and japanese eel muscle has been developed and validated. The separation condition for HPLC/UV was optimized with phenyl hexyl ($4.6{\times}150mm$, $5{\mu}m$) column with 10 mM monobasic sodium phosphate buffer (pH 2.5)/acetonitrile (50/50, v/v) as the mobile phase at a flow rate of 1.0 mL/min and detection wavelength was set at 254 nm. Residues were extracted from tissue by blending with methanol and lipid materials were removed with n-hexane. Then, the methanol extract was evaporated to dryness under a nitrogen stream, reconstituted in the mobile phase. Aliquot of the organic extract was decanted and filtered through $0.45{\mu}m$ syringe filter. The $20{\mu}L$ of the resulting solution was injected into the HPLC system. The calibration ranges were $0.5{\sim}5{\mu}g/g$ and calibration curves were linear with coefficients of correlation better than 0.95. The limits of quantification were $0.5{\mu}g/g$ for all muscles. The recoveries of bovine, porcine, chicken, flatfish and japaneseel muscles were 99.8%, 102.4%, 91.0%, 104.0% and 93.0%, respectively. The procedures were validated according to the CODEX guideline, determining specificity, linearity, accuracy, precision, quantitation limit and recovery.

• Journal of Food Hygiene and Safety
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• v.38 no.3
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• pp.89-98
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• 2023

Currently, no guidelines exist regarding the maximum residues of pesticides in edible oil which is a processed food commonly consumed in Korea. This lack of guidelines hinders the evaluation of the safety of edible oil in terms of pesticide contamination. In this study, an analysis method based on heat distillation and GC-MS/MS was established by optimizing the extraction and purification procedure for 68 pesticides. Important variables in the thermal distillation procedure included heating temperature and time, and we found the nitrogen flow rate as a mobile phase and the type of dissolving solvent were not considerably affected. The determination coefficient (R²) of the residual pesticide was 0.99 or higher, and the quantitative limit (LOQ) was 0.01-0.02 mg/L. The average recovery rate (n=5) was 66.1-120.0% and the relative standard deviation was lower than ±10% when 68 pesticides were spiked at concentrations of 0.01-0.02, 0.1, and 0.5 mg/L. In addition, the within-laboratory precision was less than ±11%, meeting the Korea Food and Drug Safety Evaluation Institute's Guidelines on Standard Procedures for Preparing Food Testing Methods (2016). Therefore, the test method developed in this study can be used as a test method for managing the safety of the residual pesticide concentration in edible oil.

• Development and Reproduction
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• v.4 no.2
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• pp.161-173
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• 2000

The aim of this study was to assess the effect of the frequency of the L$N_2$ infusion on the ultrastructure, metabolism and development of the embryo after freezing and thawing by computerized cell freezer. Two-cell embryos of ICR mouse were randomly allocated into fresh (control), high-frequency freezing (group 1) and low-frequency freezing (group 2). For fresh and frozen-thawed intact 2-cell embryos, total ceil number in the blastocyst was counted by fluorescent microscope after Hoechst 33258 staining. Relative amount of $H_2O$$_2$ was measured by DCHFDA. Intracellular location and membrane potential of the mitochondria were evaluated by staining with rhodamine 123 and JC-1. The structure of actin filament was also evaluated by confocal microscope. DNA fragmentation was assessed by TUNEL method after development into blastocyst. The survival rate of intact embryo was higher in group 1 than group 2 (50.7％ vs. 34.6％ respectively, p<0.05). The blastocyst developmental rate was significantly low in group 2 (86.7％, 76.7％ vs. 44.0％ for control, group 1 and group 2 respectively, p<0.05). Total cell number in the blastocyst was also significantly lower in group 2 than control (79.5$\pm$12.9, 71.6$\pm$8.0, and 62.5$\pm$4.7 for control, group 1 and group 2 respectively, p<0.05). The relative amount of $H_2O$$_2$ was higher in group 2 than other groups (15.3$\pm$3.0, 16.6$\pm$1.6 vs. 23.4$\pm$1.8, p<0.05). After JC-1 staining, relative intensity of mitochondria with high membrane potential was significantly lower in group 2 than control and group 1 (17.2$\pm$3.8, 17.4$\pm$1.3 vs. 13.2$\pm$2.0, p<0.05). In group 2, partial deletion and aggregation of the actin filament was found. DNA fragmentation rate was also hieher for group 2 versus other groups (30.8％, 36.0％ vs. 65.6％, p<0.05). The frequency of the L$N_2$ infusion is an important factor for the development of frozen-thawed mouse embryo. High-frequency infusion may prevent damages of cytoskeleton and mitochondria in the embryo probably by preventing the temperature fluctuation during dehydration phase. We speculate that the application of high-frequency infusion method in human embryo may be promising.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.2
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• pp.109-114
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• 1999

This study was carried out to obtain some information on the sustainability of paddy rice through the long-term variation of nitrogen use efficiency. The experiment was conducted during 30-year with the same amount of N, P, K and compost at Milyang, southern part of Korea. The results were as follows. Grain yield was increased significantly in the plots of compost incorporation only. However, yield productivity was decreased slightly in the plots with nil and unbalanced fertilization. The effects of rice straw compost on grain yield was not clear at the early crop years but was shown slightly at the late period of the experimental. The grain yield in the plots of compost incorporation at 30th crop year was come to about 80% of NPK plots. The amount of nitrogen uptaken by rice plant was the highest as $167kg\;ha^{-1}$ in NPK plus compost incorporation. Recovery efficiency)($RE_N$) was higher as 0.48~0.74 in compost incorporation plots than in other plots of balanced and unbalanced application. Average agronomic efficiency($AE-N$) and partial factor productivity from N fertilizer applied($PFP_N$) during 30 crop years in NPK plots was 12.8 kg/kg N and 37.7 kg/kg N, respectively, and difference of $AE-N$ and $PFP_N$ shown as indigenous soil nitrogen supply(INS) was higher as 28.4 kg/kg N in NPK + compost plot than NPK plot and was widened at the late period of experiment.