• Korean Journal of Environmental Agriculture
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• v.22 no.2
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• pp.130-136
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• 2003

An organophosphorus insecticide, chlorpyrifos and an arylnitrile fungicide, chlorothalonil commonly used far apple were subjected to a residual investigation under field conditions to ensure safety of terminal residues at harvest. After pesticides were applied at standard rate in apple tree fer 15 days for chlorpyrifos and 30 days far chlorothalonil, persistence of their residues in apple was investigated by several interval. At harvest, residual concentrations of chlorpyrifos and chlorothalonil in apple were 1.3 and 2.4mg/kg, respectively, and the residue levels were higher than MRL 1.0 mg/kg in Korea. As well fitted by the first-oder kinetics, biological half-lives of the pesticide residues in apple were 9.3 days for chlorpyrifos and 32.2 days for chlorothalonil. During the storage, half-lives of chlorpyrifos and chlorothalonil were 35.0 and 56.3days at room temperature, and 120.7 and 182.8 days at 412, respectively. Distribution of chlorpyrifos residue in flesh, fruit skin and stalk cavity of each apple corresponded to 0.1% 22.8% and 77.1%, respectively. In case of chlorothalonil, residue in flesh, fruit skin and stalk cavity was 4.4%, 10.4% and 85.2%, respectively.

• Journal of Applied Biological Chemistry
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• v.48 no.1
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• pp.11-15
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• 2005

Salinity of soils in greenhouse has been increased by massive application of fertilizers. Nitrogen fertilizer was most popular, and thus nitrate became the majority of soil salinity. Accumulation of nitrate led to deleterious effects on the growth and development of crops and vegetables. Microbial strains able to utilize nitrate and thus remove excess nitrate from farm land soils were isolated from 15 different soils of greenhouses and plastic film houses. Four strains able to grow in medium containing 50 mM $KNO_3$ were isolated, among which only E0461 showed high capacity of nitrate uptake. Nitrate uptake by E0461 was dependent on culture medium and was increased by addition of tryptone and peptone. Although E0461 was able to grow without tryptone and peptone, growth was slow, and no nitrate uptake was observed. Nitrate appeared to facilitate E0461 growth in the presence of tryptone and peptone. Through kinetic analysis, nitrate uptake was measured at various concentrations of nitrate, and half-life was calculated. Nitrate concentration decreased with increasing incubation period, and plot between half-lives and initial concentrations of nitrate fitted to single exponential function. These results suggest one major factor plays an important role in microbial nitrate uptake.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.3
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• pp.518-524
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• 1998

Liposomes have been widely employed as biomembrane-mimetic system and drug-delivery system. In these applications, the low stability of liposomes has been the most serious problem. They have relatively short half-lives and easily lysed through interactions with biological components. This study was performed to investigate the effects of godulbaegi extracts on the fludity of phospholipid liposomes. We used dipalmitoyl phosphatidylcholine(DPPC) liposomes which make most stable liposomes among the other phosphatidylcholines. The thermograms of the DPPC liposomal bilayers incorporated with the hexane extract of godulbaegi(Ixeris sonchifolia H.) were obtained, and the enthalpy changes and the sizes of cooperative unit of the transition were calculated. The incorporation of the Ixeris sonchifolia H. into the liposomal bilayers effectively reduced the transition temperature at which the transition from gel state to liquid-crystalline state occurs, broadened the thermogram peaks, and reduced the ratio of van't Hoff to calorimetric enthalpies. These results indicate indicate that the godulbaegi extracts (Ixeris sonchifolia H.) have significant effects on the fluidity of biological membrance.

• The Korean Journal of Pesticide Science
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• v.19 no.4
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• pp.361-369
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• 2015

This study investigated residual characteristics of bistrifluron and fluopicolide in Korean cabbage, and suggested the pre-harvest residue limits (PHRLs) based on their dissipation patterns and biological half-lives. The pesticides were sprayed on Korean cabbage in two different region under greenhouse conditions at the recommended dose, respectively. The samples for residue analysis were harvested at 0 (2 hr), 1, 2, 4, 6, 8 and 10 days after treatment, and analyzed by HPLC after clean-up with Florisil SPE. The limit of quantification (LOQ) was $0.03mg\;kg^{-1}$ for bistrifluron and fluopicolide, and the recoveries ranged from 87.2-110.6% with below 5% of RSD. The biological half-lives of field I and field II were 3.9 and 4.2 days for bistrifluron and 4.9 and 4.2 days for fluopicolide, respectively. The PHRL of bistrifluron and fluopicolide were recommended as 3.83 and $3.23mg\;kg^{-1}$ for 10 days before harvest, respectively.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.241-248
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• 2009

Pre-Harvest Residue Limit (PHRL) of bifenthrin during cultivation of grape was established by utilizing the dissipation curve and biological half-life of bifenthrin calculated from the analysis of 0, 1, 2, 3, 5, 7, 10, 15 days after treatment of bifenthrin. Grape sample was extracted and partitioned with acetonitrile and dichloromethane, respectively, and bifenthrin was determined with GC/ECD. Limit of quantitation (LOQ) of bifenthrin was 0.01 ng. Recoveries at two fortification levels of 0.1 and $0.5\;mg\;kg^{-1}$ were $104.08\;{\pm}\;1.24$ and $92.25\;{\pm}\;3.13%$, respectively. The biological half-lives of bifenthrin were about 21 days at standard application rate, while, 23 days at double application rate. Dissipation of bifenthrin on grape was not influenced by growth dilution effect. The PHRLs of bifenthrin were recommended as 0.60 and $0.55\;mg\;kg^{-1}$ for 10 and 5 days before harvest, respectively.

• The Korean Journal of Pesticide Science
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• v.21 no.1
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• pp.17-25
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• 2017

Dissipation pattern and biological half-lives of fungicides boscalid and pyraclostrobin were calculated on jujube. The pesticides were sprayed on jujube in two different field at the standard rate, respectively. The raw agricultural commodities were harvested at 0 (2 hr), 1, 3, 5, 7, 10 and 14 days after treatment, and analyzed by HPLC/DAD. The method limit of quantification (MLOQ) was $0.02mg\;kg^{-1}$ for boscalid and pyraclostrobin. The recovery ranged 101.8~109.3% with below 5% of CV (Coefficient of variation) for boscalid and 104.2~115.4% with below 5% of CV for pyraclostrobin. An average initial deposit at field 1 and field 2 samples were observed 0.40 and $0.48mg\;kg^{-1}$ for boscalid and, 0.76 and $0.57mg\;kg^{-1}$ for pyraclostrobin, respectively. The biological half-lives of field 1 and field 2 were 11.0 and 13.2 day for boscalid, and 6.1 and 12.7 days for pyraclostrobin.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.195-203
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• 2012

In this study, The effects of three different biological activated carbon (BAC) materials (each coal, coconut and wood based activated carbons) and anthracite, empty bed contact time (EBCT) and water temperature on the removal of MK, HHCB and AHTN in BAC filters were investigated. Experiments were conducted at three water temperatures (5, 15 and $25^{\circ}C$) and four EBCTs (5, 10, 15 and 20 min). The results indicated that coal based BAC retained more attached bacterial biomass on the surface of the activated carbon than the other BAC, increasing EBCT or increasing water temperature increased the synthetic musk compounds (SMCs) removal in BAC columns. The kinetic analysis suggested a first-order reaction model for MK, HHCB and AHTN removal at various water temperatures (5, 15 and $25^{\circ}C$). The pseudo-first-order biodegradation rate constants and half-lives were also calculated for MK, HHCB and AHTN removal at 5, 15 and $25^{\circ}C$. The pseudo-first-order biodegradation rate constants and half-lives of MK, HHCB and AHTN ranging from 0.0082 $min^{-1}$ to 0.4452 $min^{-1}$ and from 1.56 min to 84.51 min could be used to assist water utilities in designing and operating BAC filters for SMCs removal.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.307-313
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• 2013

This study was carried out to investigate the residual characteristics of fungicide azoxystrobin and difenoconazole in Prunus mume fruits, and establish pre-harvest residue limits (PHRL) based on dissipation and biological half-lives of fungicide residues. The fungicides were sprayed onto the crop at recommended dosage once and 3 times in 7 days interval, respectively. The samples were harvested at 0, 1, 2, 4, 6, 8, 10, 12 and 14 days after treatment. These residual pesticides were extracted with QuEChERS method, clean-up with $NH_2$ SPE cartridge, and residues were analyzed by HPLC/DAD and GLC/ECD, respectively. Method quantitative limits (MQL) of azoxystrobin were 0.03 mg $kg^{-1}$ and of difenoconazole were 0.006 mg $kg^{-1}$. Average recovery were $93.2{\pm}2.49%$, $85.5{\pm}1.97%$ for azoxystrobin at fortification levels at 0.3 and 1.5 mg $kg^{-1}$, and $100.8{\pm}6.74%$, $87.6{\pm}9.92%$ for difenoconazole at fortification levels at 0.06 and 0.3 mg $kg^{-1}$, respectively. The biological half-lives of azoxystrobin were 5.9 and 5.2 days at recommended dosage once and 3 times in 7 days interval, respectively. The biological half-lives of difenoconazole were 9.3 and 8.0 days at recommended dosage once and 3 times in 7 days interval, respectively. The PHRL of azoxystrobin and difenoconazole were recommended as 5.32 and 1.64 mg $kg^{-1}$ for 10 days before harvest, respectively.

• Korean Journal of Environmental Agriculture
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• v.30 no.1
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• pp.52-59
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• 2011

BACKGROUND: This study was performed to investigate pre-harvest residue limit (PHRL) in Chwinamul, to estimate biological half-life for residue of each pesticide. Chwinamul was sprayed with pesticides of standard and double application rate. Chlorfenapyr and fenarimol were sprayed once on Chwinamul at 10 days before harvest, and it was sampled 7 times and analysed the residual change of two pesticides. METHODS AND RESULTS: Chwinamul sample was extracted with acetonitrile and partitioned with dichloromethane, and pesticide residues were determined with GCECD. Method quantitation limit (MQL) of chlorfenapyr was 0.10 mg/kg and that of fenarimol was 0.02 mg/kg. Recoveries of chlorfenapyr at two fortification levels of 1.0 and 5.0 mg/kg were $94.2{\pm}$1.70 and $99.0{\pm}1.61%$, respectively. Recoveries of fenarimol at two fortification levels of 0.2 and 1.0 mg/kg were $92.1{\pm}2.14$ and $83.1{\pm}1.98%$, respectively. CONCLUSION(s): The biological half-lives of chlorfenapyr were about 3.5 days at standard application rate, and 3.4 days at double application rate. The biological half-lives of fenarimol were about 6.0 days at standard application rate, and 5.9 days at double application rate. The PHRLs of chlorfenapyr were recommended as 13.02 and 6.25 mg/kg for 10 and 5 days before harvest, respectively. And the PHRLs of fenarimol were recommended as 2.80 and 1.67 mg/kg for 10 and 5 days before harvest, respectively.

• Journal of Food Hygiene and Safety
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• v.34 no.2
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• pp.191-198
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• 2019

This study investigated the residual characteristics of bifenthrin and chlorothalonil in crown daisy and suggested pre-harvest residue limits (PHRLs) based on their dissipation patterns and biological half-lives. The samples for residue analysis were harvested at 0 (3 hr), 1, 3, 5, 7, 9, 11, 13, 15, 18, 22 and 26 days after treatment, and analyzed by $GC/{\mu}-ECD$ and TOF/MS. The limit of quantitation (LOQs) of bifenthrin and chlorothalonil were 0.0046 mg/kg and 0.0007 mg/kg, respectively. Recoveries ranged from $88.67{\pm}7.97%$ and $99.90{\pm}16.03%$, showing that this method is appropriate for the analysis of the pesticide residues in crown daisy. Being well within first order kinetics, the biological half-lives of the pesticide residues in crown daisy were 9.63 days for bifenthrin and 6.54 days for chlorothalonil. The PHRLs of bifenthrin and chlorothalonil were recommended as 11.70 mg/kg and 24.10 mg/kg for 26 days before harvest, respectively.