• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.369-372
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• 2007

A fast and simple high-performance liquid chromatography (HPLC) method for the simultaneous determination of four pesticides having fungicide properties has been proposed for Panax ginseng, C. A. Meyer grown for 4, 5, or 6 years. Analytical separation was performed on C18 columns using ultraviolet detector under gradient conditions. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The HPLC response for all pesticides was linear, with determination coefficients > 0.9986. The average rate of recovery for pesticides spiked with 2 fortification levels was > 72% with relative standard deviations < 9%. The limits of quantification (LOQ) ranged from 0.03 to 0.16 ppm. These LOQs were lower than the respective maximum residue limits (MRL) established by the Korean Food and Drug Administration (KFDA), except for cyazofamid. The proposed method was used to determine pesticide residue levels in samples of ginseng obtained from Jeonnam Province (Republic of Korea). None of the pesticides were found in ginseng samples grown for 4, 5, or 6 years.

• Korean Journal of Environmental Agriculture
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• v.23 no.1
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• pp.47-51
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• 2004

In order to know the residual pattern of pesticides and predict to the degradation period until below MRL we experimented procymidone and chlorothalonil for grape which were the most detected pesticide in grape by NAQS(National Agricultural product Quality management Service) survey. In this experiment we sprayed those pesticides 10 days before harvest and analyzed 0, 1, 2, 3, 5, 7, 10 day sample to establish logical equation and to calculate $DT_{50}$. Also the same day samples stored at $4^{\circ}C$ and $20^{\circ}C$, which were compared their degradation patterns. During the cultivating period, the residue amount of procymidone was changed from 1.85 mg/kg (0 day) to 0.33 mg/kg (10 day), $DT_{50}$ was 3.5 days, and chlorothalonil was changed from 5.5 mg/kg (0 day) to 3.49 mg/kg (10 day), $DT_{50}$ was 4.4 days. During the storage period, $DT_{50}$ of procymidone and chlorothalonil at $4^{\circ}C$ were 10.5 and 7.6 days, and 6.3 and 6.1 days at $20^{\circ}C$, respectively.

• Korean Journal of Veterinary Service
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• v.38 no.4
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• pp.259-264
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• 2015

We investigated the residues of 6 cephalosporins (cefquinome, cephalexin, cephalonium, cefazolin, ceftiofur, cefuroxime) using LC-MS/MS in raw meat in Seoul. This method involves extraction of the residue from the meat by distilled water and methanol followed by a manual of residue analysis published by the National Institute of Food and Drug Safety Evaluation. The recoveries ranged between 74.71~90.01% in beef, 73.37~101.40% in pork and 70.87~95.53% in chicken, respectively. The limits of detection were 0.0004~0.0563 mg/kg, and the limits of quantification were 0.001~0.169 mg/kg respectively. Residues of cephalosporins which exceeded maximum residue limits (MRL) were not exceed in any of the 287 samples. However, it is necessary to develop multi-method, which includes the active metabolites of ceftiofur.

• Korean Journal of Veterinary Research
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• v.44 no.3
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• pp.367-371
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• 2004

This report describes the determination of ceftiofur residues in milk from treatment of lactating dairy cattle by intramuscular injection of three consecutive daily doses of about 1 mg /kg BW, the recommended label dosing. The separation of ceftiofur was achieved on $C_1_8$ reverse phase column. The mobile phase consisted of 0.1% trifluoracetic acid in water (A) and 0.05% acetic acid in acetonitrile (B) and grediently flowed at the flow rate of 0.4 mL/min. As a result of analysis of blank raw bovine milk samples, matrix interference was not shown. Limit of detection and limit of quantitaion was 0.5 ng/mL and 1 ng/mL, respectively. The values of precision and recovery satisfied the guideline of National Veterinary Research and Quarantine Service (NVRQS, Korea). The mean residual concentration of ceftiofur in milk did not exceed 3.71 ng/mL when ceftiofur was administered intramuscularly to lactating dairy cattle for 3 consecutive days at 1 mg/kg of BW per day. It is much lower than the proposed MRL (100 ng/mL) of ceftiofur in milk.

• Journal of Biomedical Engineering Research
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• v.18 no.4
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• pp.421-428
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• 1997

Magnetic field sensors made from superconducting quantum interference device (SQUID) are the most sensitive low-frequency sensors available, enabling measurements of extremely weak magnetic fields from the brain. Neuromagnetic measurements allow superior spatial resolution, compared with the present electric measurements, and superior temporal resolution, compared with the fMRl and PET, providing useful informations for the functional diagnoses of the brain. We developed a 4-channel SQUID system for neuromagnetic applications. The main features of the system are its simple readout electronics and compact pickup coil structure. A magnetically shielded room has been constructed for the reduction of environmental magnetic noises. The developed SQUID system has noise level lower than the magnetic noise from the brain. Magnetic field signals of the spontaneous r-rhythm activity and auditory evoked magnetic fields have been measured.

• Korean Journal of Veterinary Service
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• v.45 no.3
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• pp.229-236
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• 2022

This study describes an analytical method based on LC-MS/MS for the quantitation of 5 fluoroquinolones (Enrofloxacin, Ciprofloxacin, Marbofloxacin, Norfloxacin and Danofloxacin) in meat, and was applied to 230 meat samples for validation. Quantitation was performed based on a matrix-matched calibration to compensate for the matrix effect on the electrospray ionization. Good linear calibrations (R²≥0.998) were obtained for all fluoroquinolones at 6 concentrations of 1~50 ㎍/kg. Satisfied recoveries of all fluoroquinolones were demonstrated in spiked meat at three levels from 10 to 50 ㎍/kg. The recoveries ranged between 75.8~99.2% in beef, 80.1~99.6% in pork and 72.2~99.8% in chicken, respectively. The limits of quantitation (LOQs) for fluoroquinolones ranged from 0.7 to 3.2 ㎍/kg. We also monitored fluoroquinolones residue in the sample (beef 107, pork 71, chicken 52) using LC-MS/MS. Residues of fluoroquinolones which exceeded maximum residue limits (MRL) were not exceed in any of the 230 samples.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1913-1915
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• 1999

The ${\beta}-SiC+ZrB_2$ ceramic composites were hot-press sintered and annealed by adding 1, 2, 3wt% $Al_2O_3+Y_2O_3$(6 : 4wt%) powder as a liquid forming additives at $1950^{\circ}C$ for 4h. In this microstructures, no reactions were observed between $\beta$-SiC and $ZrB_2$, and the relative density is over 90.79% of the theoretical density and the porosity decreased with increasing $Al_2O_3+Y_2O_3$ contents. Phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H, 4H), $ZrB_2$, $Al_2O_3$ and $\beta$-SiC(15R). Flexural strength showed the highest of 315.46MPa for composites added with 3wt% $Al_2O_3+Y_2O_3$ additives at room temperature. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed the highest of $5.5328MPa{\cdot}m^{1/2}$ for composites added with 2wt% $Al_2O_3+Y_2O_3$ additives at room temperature.

• Korean Journal of Environmental Agriculture
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• v.37 no.2
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• pp.97-103
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• 2018

BACKGROUND: Dissipation of acetamiprid and thiamethoxam in greenhouse grown chard samples was evaluated at 5 intervals including the pre-harvest interval after application. This study was conducted to determine the residue levels, the biological half-lives and dissipation rate of acetamiprid and thiamethoxam in chard under controlled conditions. METHODS AND RESULTS: Acetamiprid and thiamethoxam were applied in accordance with good agricultural practices for chard. Chard samples were collected at 0, 1, 2, 3, 5, 7, 10 and 14 days after application. Quantitaion was performed by HPLC-DAD system with C18 column. Limit of quantification (LOQ) of acetamiprid and thiamethoxam were both 0.02 mg/kg for chard. The recovery of acetamiprid and thiamethoxam were 77.8~107.5% and 94.3~108.6% at two concentration levels. The half-lives of pesticide dissipation in chard for two fields were 11.9 and 8.2 days for acetamiprid and 3.6 and 3.3 days for thiamethoxam respectively. The dissipation rate of acetamiprid and thiamethoxam were estimated according to the statistics method with a 95% confidence. CONCLUSION: Dissipation of acetamiprid and thiamethoxam in chard were determined under greenhouse. The concentration of acetamiprid and thiamethoxam in chards at 0 days after application were below specified by Korean MRL. Dissipation rate constant will be useful to set the pre-harvest residue limit for public health and consumer protection.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.52-58
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• 1995

5-methyltryptophan（5MT） resistant mutant plants （MRl） were analyzed for characterization of anthranilate synthetase （AS） and tryptophan synthetase （TS） enzymes. The enzyme was measured in crude extracts from MR1 and control seedlings of Danggin inbred line. There was no significant difference in the level of AS between MR1 and control seedlings when grown on MS medium without 5MT. However, MR1 seedlings grown on MS medium with 25mg/L 5MT showed the level of AS twice higher than that of control seedlings. The activity of AS was inhibited to 50％ in untreated plants when 4mg /L L-tryptophan was added to their extracts. Extracts from MR1 plants required about four times higher concentration of amino acid to cause equal inhibition. In the TS assay, the activity observed in MR1 seedlings was four times higher than that of control seedlings. We have also isolated and sequenced the gene which encoding the tryptophan synthetase B subunit （TSB） from maize. The gene encodes polypeptides with high homology to TSB isolated from other plants, and is expressed in all the developmental stages examined. Northern hybridization analysis indicated that the gene expression in MR1 seedlings grown on MS medium showed a higher level than in control seedlings.

• Korean Journal of Environmental Agriculture
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• v.15 no.4
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• pp.434-441
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• 1996

This study was conducted to clarify the degradation pattern, safety evaluation and penetration ratio of benomyl and bitertanol to apple used as postharvest fungicides during CA(controlled atmosphere) and cold storage. In CA storage, the degradation of benomyl and bitertanol in stored apple was slow at the early stage, while that in cold storage was, on the contrary, faster at the early stage. The initial concentrations of benomyl and bitertanol in apples applied at the standard application concentrations were 2.24 and 1.54mg/kg, respectively, and their residual amounts were below the maximum residue limits, 1mg/kg at 135 and 96 days in CA storage, 115 and 70 days in cold storage, respectively. The half-lives of benomyl and bitertanol in stored apples were 124 and 130 days in CA storage, 101 and 111 days in the cold storage, respectively, indicating that the degradation was faster in cold storage than in CA storage. The residual amount of benomyl and bitertanol in stored apples was retained more in peels than in pulps of apples.