• Korean Journal of Environmental Agriculture
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• v.28 no.4
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• pp.419-426
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• 2009

This study was conducted to know the biological half-lives and dissipation patterns of fungicides, pyrimethanil, chlorothalonil and tetraconazole in Korean melon under green house condition. The instrument for analyzing pyrimethanil and chlorothalonil was HPLC equipped with UV detector. Initial residue amounts of pyrimethanil were 0.16 mg/kg at recommended rate and 0.28 mg/kg at double recommended rate in Korean melon. The biological half-lives of pyrimethanil were 11.2 days at recommended rate and 10.1 days at double recommended rate in Korean melon. In case of chlorothalonil, initial residue amounts of chlorothalonil were 0.06 mg/kg at recommended and 0.11 mg/kg at double recommended rate in Korean melon. The biological half-lives of chlorothalonil in Korean melon were 3.4 days at recommended rate and 6.6 days at double recommended rate. The instrument for analyzing tetraconazole was GLC equipped with electron capture detector. Initial residue amounts of tetraconazole were 0.14 mg/kg at recommended and 0.22 mg/kg at double recommended rate in Korean melon, respectively. The biological half-lives of tetraconazole were 9.6 days at recommended rate and 18.5 days at double recommended rate in Korean melon.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.139-142
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• 2001

The one of important parameter involved in the calculation of internal radiation dose to the human body is the biological half-life of the radionuclide. The biological half-life is population specific and may differ from one population group to another. So the effective half-life of tritium exposure based on urinal bioassay measurement of Wolsong Nuclear Power Plants was investigated and studied.

• Journal of Food Hygiene and Safety
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• v.23 no.2
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• pp.129-136
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• 2008

Three benzimidazole pesticides commonly used in korean lettuce were subjected to a field residue trial to ensure safety of terminal residue in the harvest. The residual patterns of three benzimidazole pesticides, which were carbendazim, benomyl and thiophanate-methyl were examined after applying with the recommended dose in two types of korean lettuce (Chima and Chuckmeon) and their DT50 were calculated. In Chima lettuce, biological half-lives of carbendazim, benomyl and thiophanate-methyl were 2.56, 1.37 and 2.54 days, respectively and their required time under MRL(5.0 mg/kg as carbendazim) were 4.5, 2.2 and 1.0days. In Chuckmeon lettuce, biological half-lives of them were 3.41, 1.70 and 4.20 days, respectively and their required time under MRL were 5.4, 1.9 and 0.5days.

• Korean Journal of Environmental Agriculture
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• v.28 no.3
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• pp.281-288
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• 2009

The strobilurin fungicides, azoxystrobin and kresoxim-methyl, were investigated to know the biological half-lives and dissipation patterns in Korean melon under plastic film house condition. Used pesticides for field application were 20% azoxystrobin of suspension concentrate and 47% kresoxim-methyl of water dispersible granule. Two pesticides were sprayed at recommended and double dose rate. Pesticide residues in Korean melon were analyzed until 14 days after application. The azoxystrobin was analyzed by HPLC equipped with UV detector after cleanup with florisil glass column. Initial residue concentrations of azoxystrobin in Korean melon at recommended and double dose rate were 0.09 mg/kg and 0.14 mg/kg, respectively. Those were less than 0.2 mg/kg maximum residue limit of Korean melon established by KFDA. The biological half-lives of azoxystrobin in Korean melon were 4.7 days at recommended dose rate and 7.8 days at double dose rate. Initial concentrations of kresoxim-methyl which was analyzed by GLC-ECD in Korean melon at recommended and double dose rate were 0.10 mg/kg and 0.23 mg/kg, respectively. Those were less than 1.0 mg/kg, MRL. The biological half-lives of kresoxim-methyl in Korean melon were 4.1 days at recommended dose rate and 4.8 days at double dose rate. The residue amounts of both pesticide was lower than MRL and biological half-lives were not so long. Because the weight of Korean melon under plastic film house condition was fast increased during cultivation.

• Korean Journal of Environmental Agriculture
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• v.37 no.3
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• pp.213-220
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• 2018

BACKGROUND: This study was carried out to determine characteristics of residual pesticides in time-dependent manner and calculate half-lives of the residual pesticides in fresh and dried Chinese matrimony vine. In addition, processing factors were calculated based on the residual concentrations in them. METHODS AND RESULTS: The test pesticides, etofenprox and fenitrothion, were sprayed onto the Chinese matrimony vine plants at once or twice (at seven-day interval) and then samples were collected at 0 (after 3 hours), 1, 3, 5 and 7 days after the last spraying. Dried samples were prepared in hot-air drying oven at $60^{\circ}C$ for 48 hours until water content of less than 20%. Residual concentrations of etofenprox in fresh and dried samples decreased by 54.0-60.9% after 7 days of the last pesticide-application. In case of fenitrothion, the concentrations were found to have decreased by 69.2-76.5%. Processing factors of etofenprox were 2.6-3.0 for the one-time spraying and 2.5-3.0 for the two-time spraying and those of fenitrothion were found to be 1.5-22 for the one-time spraying and 1.6-2.0 for the two-time spraying. First half-lives of etofenprox and fenitrothion in fresh and dried samples ranged from 5.0 to 6.3 and from 3.4 to 4.0 days, respectively. The third half-lives were found to be 15.0-18.9 and 10.2-12.1 days, respectively. CONCLUSION: Residual concentrations of the tested pesticides in the studied crop decreased, but those in the dried samples appeared to have increased. In addition, processing factor and half life were constant regardless of spraying times.

• The Korean Journal of Pesticide Science
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• v.9 no.3
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• pp.231-236
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• 2005

This study was conducted to determine the amounts of pesticide residues after treatment of criterion dose with 4 pesticides(tolclofos-m, folpet, procymidone, and triflumizole) under cultivated period and to compare the biological half-life of pesticides with 6 kinetic models(first, zero and second order kinetics, power function, elovich and parabolic model) and to establish proposed field tolerance using biological half-lives. Recovery of 4 pesticides form strawberry was ranged from 85.1 to 105.5%. For all of 4 pesticides, dissipation rate was over 73% at 5 days after application. Among 6 kinetic models, first order kinetic model (FO) was best fit to describe the relationship between residual pattern of pesticides and time. Therefore, half-lives were calculated by FO for establishing the field tolerance. These results showed that half-life should be calculated by comparative best fit kinetic model and field tolerance can help to prevent unacceptable agricultural products from marketing. It is good for both consumers and farmers having safe agricultural products and financial benefits, respectively.

• Korean Journal of Environmental Agriculture
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• v.32 no.2
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• pp.136-141
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• 2013

BACKGROUND: This study was performed to establishment the PHRLs of peach during cultivation period, and also to estimate biological half-lives for residues of fenarimol and flufenoxuron. METHODS AND RESULTS: The extracted samples of fenarimol were analyzed by GC-ECD and the flufenoxuron extracted samples were analyzed by HPLC-DAD. Recoveries of fenarimol at two fortification levels of 0.1 mg/kg, 0.5 mg/kg were $93.69{\pm}6.56$(%) and $94.45{\pm}1.60$ (%), respectively. And recoveries of flufenoxuron at two fortification levels of 0.1 mg/kg, 0.5 mg/kg were $106.73{\pm}5.90$(%) and $96.37{\pm}6.66$(%), respectively. CONCLUSION(S): The biological half-lives of fenarimol in single treatment and triple treatment were 3.5day and 3.8day. that of Flufenoxuron was also 7.1day and 4.9day, respectively. The PHRL of fenarimol were recommended as 1.5 mg/kg for 10day before harvest and the PHRL of flufenoxuron were recommended as 1.4 mg/kg for 10day before harvest.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.45-51
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• 2012

BACKGROUND: This study was carried out to establish pre-harvest residue limit of fungicides pyrimethanil and trifloxystrobin in persimmon, based on dissipation and biological half-lives of two fungicides residue. METHODS AND RESULTS: Both pyrimethanil and trifloxystrobin were extracted with acetonitrile, clean-up with $NH_2$ SPE cartridge and residue were analyzed by HPLC/DAD. Limit of Detection was 0.01 mg/kg. Average recovery were $81{\pm}1.62%$, $98{\pm}1.58%$ of pyrimethanil, and $91{\pm}2.94%$, $98{\pm}1.25%$ of trifloxystrobin at fortification levels at 0.1 and 0.5 mg/kg, respectively. CONCLUSION: The biological half-lives of pyrimethanil were 15.6 and 11.6 days at sprayed with recommended and double dosage, respectively. The biological half-lives of trifloxystrobin were 10.4 and 10.3 days at sprayed with recommended and double dosage, respectively. The pre-harvest residue limit of pyrimethanil and trifloxystrobin were recommended as 2.69 and 0.83 mg/kg for 10 days before harvest, respectively.

• Korean Journal of Environmental Agriculture
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• v.36 no.1
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• pp.50-56
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• 2017

BACKGROUND: The present study was carried out to identify the residue patterns of insecticide pyridalyl and fungicide fluopicolide in watermelon and calculate the biological half-lives for establishing the pre-harvest residue limits (PHRLs). METHODSANDRESULTS:The watermelon samples for residue analysis were harvested 7 times during 0~10 days (Field 1) and 0~20 days (Field 2) after treatment of pesticides on watermelon in two different fields at the recommended dose, respectively. The residue analysis was conducted with HPLC/UVD. The method limit of quantitation (MLOQ) were set at 0.05 and 0.02 mg/kg, respectively, and overall mean recoveries were 81.2~90.5% for pyridalyl and fluopicolide. The residues in sample were stable for 43~47 days. The initial residue amount in field 1 and 2 were 0.12~0.16 mg/kg for pyridalyl and 0.23~0.24 mg/kg for fluopicolide, which were below maximum residue limit (MRL). The biological half-lives in field 1 and 2 were 26.9 and 17.9 days for pyridalyl and 16.6 and 94.2 days for fluopicolide, respectively. CONCLUSION: The PHRL for watermelon were estimated as 0.21 and 1.03 mg/kg for pyridalyl and flopicolide at 10 days before harvesting. The residue patterns of pyridalyl and fluopicolide were characterized by a very slow decrease of residue levels in watermelon.

• Current Research on Agriculture and Life Sciences
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• v.31 no.4
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• pp.272-279
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• 2013

The dissipation patters of the triazole fungicides flusilazole and myclobutanil in apples were investigated to establish the biological half-lives and pre-harvest residue limits (PHRLs). The residual amounts of the fungicides sprayed with single or triple doses were below the maximum residue limits (MRL) for apples established by Ministry of Food and Drug Safety. The dissipation constants of the fungicides in the apples were 0.0513 for flusilazole and 0.0244 for myclobutanil meaning their biological half-lives were calculated as 6.2-6.7 days for flusilazole and 13.3-24.8 days for myclobutanil. The PHRLs calculated using the dissipation constants indicated that the residual amounts of flusilazole and myclobutanil in the apples at the harvesting date would be below the MRLs if their residual amounts were 0.43 and 0.59 mg/kg, respectively, at 7 days prior to harvesting the apples.