• The Korean Journal of Pesticide Science
• /
• v.14 no.4
• /
• pp.381-393
• /
• 2010

In order to monitor the residual characteristics of the pesticides in leafy vegetables selling at wholesale markets and traditional markets in Cheongju, a total of 180 samples of 15 leafy vegetables, such as broccoli, celery, chard, chicory, Chinese vegetable, Chwinamul, crown daisy, Korean cabbage, leek, lettuce, perilla leaves, Shinsuncho, spinach, welsh onion and young radish, were purchased from the wholesale markets and traditional markets in June and August in 2010 and the pesticide residues in them were analyzed by multiresidue analysis method using GLC, HPLC and GC-MSD. Seven pesticides were detected from 12 samples out of total 180 samples collected, representing detection rate was 6.7%. In case of the samples collected from markets in June, four pesticides including tefluthrin were detected from six samples and in case of the samples collected from markets in August, three pesticides including pendimethalin were detected from three samples. The MRL-exceeding rate of pesticides detected from leafy vegetables was 0.6%. The pesticide exceeded its MRL was azoxystrobin detected from crown daisy and many pesticides were not registered to the crops, excepting that azoxystrobin detected from Chwinamul and tefluthrin from leek. Estimated daily intakes (EDIs) of the pesticides detected from leafy vegetables were less than 7% of their acceptable daily intakes (ADIs), representing that residue levels of the pesticides detected were evaluated as safe.

• Microbiology and Biotechnology Letters
• /
• v.10 no.2
• /
• pp.123-132
• /
• 1982

These experiments were conducted to investigate the enzymatic characteristics of the purified $\alpha$-amylase (F-2A) of Bacillus circulans F-2 and the digestion rate of various starches. 1. The molecular weight was estimated to be 93000 by SDS-polyacrylamide disc gel electrophoresis. The isoelectric point was about pH 5.0. The optimum pH for the enzyme action was 6.0-6.5 and the stable pH ranged pH 5.5-12.0. The optimum temperature was 6$0^{\circ}C$, and the purified $\alpha$-amylase was stable below 4$0^{\circ}C$. 2. The purified $\alpha$-amylase was activated by Mn$^{＋＋}$ and Co$^{＋＋}$, whereas it was inhibited by Ag$^{＋}$, HT$^{＋＋}$, Cu$^{＋＋}$ and Pb$^{＋＋}$. 3. The purified $\alpha$-amylase is considered to have no sulfhydryl residue essential for its catalytic activity. 4. Michaelis constant (Km) was 1.704 mg/$m\ell$. Activation energy between 25-4$0^{\circ}C$ was 12.297 Kcal/mole, and between 40-6$0^{\circ}C$, it was 7.831 Kcal/mole. 5. The hydrolysis product from soluble starch, amylose and amylopectin in the early stage of hydrolysis was G$_{6}$, and as hydrolysis proceeds, G$_4$and G$_2$appeared. 6. Products from each oligosaccarides are as follows: G$_4$longrightarrow G$_2$＋ G$_2$,G$_3$ ＋G$_1$,G$_{5}$longrightarrow G$_4$＋G$_1$,G$_{6}$longrightarrowG$_4$＋ G$_2$,G$_{7}$ G$_4$,G$_{8}$longrightarrow G$_4$＋G$_4$, 7. On raw potato starch, raw sago starch and raw yam starch, the purified enzyme exhibited a remarkably high digestion rate than Porcine pancreatic amylase and Streptococcus bovis amylase.

• Korean Journal of Agricultural Science
• /
• v.4 no.2
• /
• pp.229-238
• /
• 1977

Sumithion and EPN residues on grapes, EPN and Diazinon on chinese cabbage, Parathion on peaches, Dimethoate on tomatoes, and EPN and Malathion on cucumber were analyzed in terms of 0, 3, 7, 14, 21 and 30 days after last application for the pesticides safty use. From the disappearance rate for various organo-phosphate insecticides on vegetables and fruit crops, following results are obtained. 1. On Chinese cabbage, Diazinon residues were 0.25~0.38p.p.m three weeks after one application, and EPN were 1.39~2.69p.p.m seven days after one application and 0.96~2.34p.p.m two weeks after twice application. 2. EPN residues on grapes were 1.09~1.80p.p.m seven days after one application and Sumithion were 0.17~0.53p.p.m fourteen days after one application. 3. On peaches, Parathion residues were 0.40~0.61p.p.m two weeks after last application. 4. Dimethoate residues on tomatoes were 0.141p.p.m seven days after four times application. 5. On cucumber, EPN residues were 2.11~2.14p.p.m three days after twice application, and Malathion were 0.46p.p.m 3 day after four times application but 0.062~0.025p.p.m three days after last application. 6. Rate of degradation of organo-phosphate chemicals is inversely related to half-life of its. 7. Minimum intervals between last treatment and harvest to prevent unsafty residues are as follows. 7 days for EPN with one application and 14 days with twice application on chinese cabbage, 3 days on cucumber and 7 days on grape, 14 days for parathion, 7 days for dimethoate on tomatoes, 0 to 3 days for Malathion on cucumber, 21 days for Sumithion on grape, 21 days on chinese cabbage for Diazinon.

• Resources Recycling
• /
• v.31 no.1
• /
• pp.65-77
• /
• 2022

A study was conducted in Korea on the leaching behavior and possibility of recovery of vanadium and other valuable metals from domestic vanadium titanomagnetite (VTM) by direct acid leaching. In this study, a VTM concentrate containing 0.8% V₂O₅ was used, and the ratio of magnetite to ilmenite was calculated as 1.9:1 by using the HSC program. The leaching behavior of vanadium from the VTM was similar to that of iron, and it was affected by the concentration of sulfuric acid and temperature. Further, titanium could be leached in the form of TiOSO₄ at a temperature higher than 75℃. To improve the leaching efficiency of V, Fe, and Ti in VTM, reductive sulfuric acid and oxidative sulfuric acid leaching were performed. When Na₂SO₃ was used as a reducing agent, the leaching rate of vanadium was 80% of that in that case of leaching by sulfuric acid. Similarly, the leaching rate of titanium increased from 20% to 50%. When Na₂S₂O₈ was used as an oxidation agent, most of the vanadium was leached, and the main residue found by XRD analysis was ilmenite. In studies on the possibility of recovering valuable metals, the selective extraction of metals is hardly achieved by solvent extraction from oxidation leaching solutions; however, in this study, Cyanex 923, a solvation extractant from reductive leaching solutions, could selectively extract Ti.

• Horticultural Science & Technology
• /
• v.19 no.4
• /
• pp.596-601
• /
• 2001

This study was carried out to determine the effect of base carriers such as zeolite or vermiculite on change of concentration of polyoxyethylene laury ether[$C_{12}H_{25}O(C_{2}H_{4}O)_{3}H$, PLE] and on initial wetting of peat-vermiculite medium in the development of a soil wetting agent using the mixture of PLE and polyoxyethylene+polyppro-pyleneoxide tridecylether (1:1, w/w, CM-1). The concentration of PLE in the treatment of vermiculite was higher than that of zeolite during the period from 2 to 6 weeks. The cumulative concentration of PLE released in the treatment of vermiculite was about $2800mg{\cdot}L^{-1}$ and zeolite was about $2300mg{\cdot}L^{-1}$. The treatments of PLE+CM-1 with zeolite or vermiculite as a carrier were effective in initial water retention of root media having more than 510 mL of water per pot, where as those of $AquaGro^{G}$ and control had 490 mL and 400 mL of water per pot, respectively. In the evaporative water loss, the treatment of zeolite and $AquaGro^{G}$ were faster than that of control and vermiculite. The control treatment had the fastest water movement in and the highest volume of water infiltrating into root medium among all treatments. Increased application rate of PLE+CM-1 did not increase water retention capacity. The treatment of $0.6g{\cdot}L^{-1}$ had the highest evaporative water loss and that of $0.3g{\cdot}L^{-1}$ had the highest amount of water infiltrating into root media among all other treatments.

• Korean Journal of Soil Science and Fertilizer
• /
• v.23 no.1
• /
• pp.21-25
• /
• 1990

The amounts of monosaccharides in acid hydrolysates of decomposing plant residues under laboratory conditions were determined. Straw of cereal rice and barley, wild grass cutting, and litters of deciduous and coniferous forest trees were treated to decompose for 90 days. Samples for the analysis of mono-saccharides were taken at 3 different periods of incubation. 1. Fractions of monosaccahrides in plant residues steadily decreased with the time of decomposition. In some samples there appeared an intermediate stages where the fractions reached the highest level. 2. Decomposition of barley straw occured at a faster rate than that of rice straw, and so did the decomposition of deciduous litter than that of coniferous litter. 3. Cereal crop residues of rice and barley were richer in monosaccharides than residues of wild grass cutting and forest litters. 4. Distiction between monosaccharides of plant origin and those of microbial origin was not possible to make in this study. 5. Glucose was the predominent monosaccharide and fucose was the monosaccharide contained in the smallest amount. No measurable ribose was detected from any sample. 6. The relative proportion of galactose in creased with the time of incubation. 7. In general, the proportion of fucose decreased with time and so did that of rhamnose, rhamnose of rice straw residue being the exception. 8. The orders of abundance of monosaccharides after decomposition of 90 days were as the following: in rice straw; glucose > xylose > arabinose > galactose > rhamnose > mannose > fucose, in barley straw; glucose > xylose > arabinose > galactose> mannose > rhamnose > fucose, in wild grass cutting; glucose > xylose > galactose arabinose> rhamnose mannose > fucose, in deciduous litter; glucose > arabinose > xylose galactose > mannose > rhamnose = fucose, and in coniferous litter; glucose > xylose > galactose > arabinose mannose > rhamnose > fucose.

• Korean Journal of Food Science and Technology
• /
• v.45 no.5
• /
• pp.531-536
• /
• 2013

We developed a simple, sensitive, and specific analytical method for prometryn using gas chromatography-mass spectrometry (GC-MS). Prometryn is a selective herbicide used for the control of annual grasses and broadleaf weeds in cotton and celery crops. On the basis of high specificity, sensitivity, and reproducibility, combined with simple analytical operation, we propose that our newly developed method is suitable for use as a Ministry of Food and Drug Safety (MFDS, Korea) official method in the routine analysis of individual pesticide residues. Further, the method is applicable in clams. The separation condition for GC-MS was optimized by using a DB-5MS capillary column ($30m{\times}0.25mm$, 0.25 ${\mu}m$) with helium as the carrier gas, at a flow rate of 0.9 mL/min. We achieved high linearity over the concentration range 0.02-0.5 mg/L (correlation coefficient, $r^2$ >0.998). Our method is specific and sensitive, and has a quantitation limit of 0.04 mg/kg. The average recovery in clams ranged from 84.0% to 98.0%. The reproducibility of measurements expressed as the coefficient of variation (CV%) ranged from 3.0% to 7.1%. Our analytical procedure showed high accuracy and acceptable sensitivity regarding the analytical requirements for prometryn in fishery products. Finally, we successfully applied our method to the determination of residue levels in fishery products, and showed that none of the analyzed samples contained detectable amounts of residues.

• The Korean Journal of Pesticide Science
• /
• v.17 no.4
• /
• pp.256-263
• /
• 2013

The field lysimeter study was undertaken to investigate influence of agricultural practice and topography on runoff and erosion loss of fluazinam from the sloped land grown pepper. The WP type formulation was applied on July in 2003~2005. The wash-off rates were from 1.4% to 8.4% of the applied fluazinam. The runoff losses of fluazinam from a series of pepper grown-lysimeter plots were 0.14~0.90% in the first year, 0.01~0.04% in the second year and 0.16~0.37% in the third year for the mulched contour ridge plots, 0.47~1.59% for the mulched up-down direction ridge plots and 0.07~1.05% for the no-mulched contour ridge plots as the control, and they increased with slope degree. Concentrations of fluazinam in runoff water ranged mostly to 10 ${\mu}gL^{-1}$ at the first runoff event. Erosion rates from plots except the mulched up-down direction ridge plots was 0.00~0.21% for 10% and 20% slope-plots and 0.15~1.05% for 30% slope-plots with different slope degrees. Erosion rates from the mulched up-down direction ridge plots were 0.47~1.59% for 10% slope-plots and 0.75~1.05% for 20% slope-plots. Residues of fluazinam in soil at ten days after the application ranged from 0.007 mg $kg^{-1}$ to 0.059 mg $kg^{-1}$ except the soil under the mulch. After then the fluazinam residue in soil was dissipated at the rate of 20 days of half-life to below 0.01 mg $kg^{-1}$ at 60 days after the application.

• Journal of Food Hygiene and Safety
• /
• v.35 no.3
• /
• pp.225-233
• /
• 2020

By the standards and specifications for hygiene products, three test methods for formaldehyde are specified for each item type of hygiene product. After derivatization using acetylacetone and 2,4-dinitrophenylhydrazine (2,4-DNPH), formaldehyde is analyzed by spectrophotometer and high-performance liquid chromatography (HPLC). Validation of the three test methods was performed on tissue, diaper lining and waterproof layer, and panty liner products. The results of linearity (R²), limit of detection (LOD), limit of quantification (LOQ), recovery rate (%) and reproducibility (%), showed that all three methods are suitable for analyzing formaldehyde in hygiene products. After derivatization with 2,4-DNPH and cetylacetone, formaldehyde was analyzed at 0, 3, 6, 9, 24 and 48 hours by HPLC. Formaldehyde derivatized with 2,4-DNPH showed no statistically significant change in formaldehyde peak area over time (P>0.05). But, acetylacetone-derivatizated formaldehyde showed a negative correlation coefficient (r) over time (P<0.01). We investigated the residual amounts of formaldehyde in 205 hygiene products distributed in Busan. Among 74 disposable diaper products tested, 73 had low concentrations of formaldehyde (0.13-29.87 mg/kg). Moreover, formaldehyde was not detected in any of 78 tissue, 27 disposable paper towel, 12 disposable dishcloth, 7 paper cup, one brand of paper straw and 6 disposable napkin products.

• The Korean Journal of Pesticide Science
• /
• v.10 no.2
• /
• pp.99-106
• /
• 2006

Chlorothalonil and imidacloprid sprayed onto the green peppers were degraded more faster at outdoor than in greenhouse. These results were affected by dew and photodegration, considering no rain during the experimental period. Chlorothalonil, esfenvalerate and imidacloprid in green pepper, green twist pepper and sweet pepper did not show any residual pattern, because green peppers are one of the continuous harvesting crops and pesticides could not be sprayed homogeneously on them. When green peppers were pickled with soy sauce and green twist peppers were fried with vegetable oil, the amounts of pesticides such as alpha-cypermethrin, bifenthrin, chlorfenapyr, esfenvalerate and imidacloprid were diminished to the levels of about $30{\sim}71$ and $20{\sim}41%$, respectively. Esfenvalerate and imidacloprid could not be detected in 2 month-old hot pepper paste. The removal rates of pesticide residues in leaves of green peppers were about $22{\sim}37%$ by washing, about $74{\sim}95%$ by parboiling, and about $17{\sim}55%$ by drying after parboiling.