• The Korean Journal of Pesticide Science
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• v.19 no.3
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• pp.218-229
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• 2015

The proficiency testing for the residue laboratories of pesticide registration was conducted in order to improve the reliability and the ability for pesticide residue analysis. On November 2012 the testing was carried out using the soil collected and kept as the moistened state for five years, which was expected to very low residue levels of pesticides. The soil was fortified with azoxystrobin, imidacloprid and methabenzthiazuron in a manner similar to prepare soil samples for indoor soil degradation test, and then sub-samples were prepared for the distribution to participants. Some of them were randomly selected for confirm of homogeneity and to ensure the stability of samples at room temperature. Samples were consisted of two soils treated as different levels, one of which was used to the assessment and another used to confirm. In addition, provided three standard solutions, respectively concentration of 10 mg/L, and untreated soil. Forty eight institutions submitted results. The medians of results were used as the assigned values for pesticide residues. Fitness for purpose standard deviation of proficiency test was calculated by applying 20% RSD as the coefficient of variation allowed in the soil residue test. Z-score was applied for evaluation of individual pesticides, and the average of the absolute value of the Z-score for the overall assessment of pesticides. Laboratories evaluated the absolute value of the Z-score less than 2 to fit the case of azoxystrobin were 48, imidacloprid and methabenzthiazuron 46.

• Food Science and Biotechnology
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• v.14 no.4
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• pp.456-460
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• 2005

To enforce the maximum residue limit for residual hexane (0.005 g/kg) in commercially available Korean vegetable oil, convenient and accurate quantification methods were investigated. Using dual surrogate standards, pentane and heptane were dissolved in ethanol, and then added to hexane-tree sunflower oil for setting up the calibration curve. Gas Chromatograph-Flame Ionization Detector with a porous layer open tubular column, indicated good chromatographic separation of hexane from other inhibiting matrix components. The lowest calibration level was $0.5\;{\mu}g/g$, not exceeding a relative standard deviation of 10% (RSD%), and 1.0\;{\mu}g/g$ not exceeding a deviation of 22% RSD% using heptane as an internal standard for the Static headspace analysis by using a headspace auto-sampler and manual injection, respectively. The residual hexane was detected in nine of the samples among 87 vegetable oil samples purchased on the local market.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.559-563
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• 2012

An analytical method for the simultaneous determination of veterinary medicines (amprolium and decoquinate) in cattle and chicken's muscle by HPLC/UV-vis was established. Samples were extracted by a HLB (Hydrophilic-Liphophilic Balance) cartridge with acetonitrile and methanol. Prior to HPLC injection, a mixture solvent (Water:MeOH, 1:1) was utilized as a reconstitution solvent. Chromatographic separation was achieved with a C18 column ($250{\times}4.6mm$, $5{\mu}m$) using gradient elution with 20 mM HFBA and MeOH:ACN (1:1.8). The calibration curves from the spiked blank matrix showed good linearity (above $r^2$=0.997) in the concentration range of $0.13-12.0mg\;kg^{-1}$. The relative recovery (accuracy) and limit of quantitation (LOQ) were in the range of 78.5-107.1% and $0.13-0.42mg\;kg^{-1}$, respectively. The developed method can be used to determine under the MRL (Maximum Residue Limits) levels of veterinary medicines in animal tissues.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1173-1178
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• 2008

A simple and sensitive high-performance liquid chromatographic method was developed for the simultaneous identification of enrofloxacin and its active metabolite ciprofloxacin in chicken muscle. Norflorxacin imprinted polymers synthesized in water-containing systems show high selectivity to enrofloxacin and ciprofloxacin in an aqueous environment. Using these water-compatible imprinted polymers as selective adsorbents in the solid-phase extraction of enrofloxacin and ciprofloxacin from chicken samples, the remaining biological matrix could be quickly washed out from the imprinted column while enrofloxacin and ciprofloxacin were selectively retained and enriched. Analytical separation was performed on a $C_{18}$ column using acetonitrile-water as a mobile phase and fluorescence detection. Good linearity was obtained from 0.8 to 500 ng/g (r > 0.998) with relative standard deviation of less than 3.9%. The mean recoveries of enrofloxacin and ciprofloxacin from chicken muscle were 80.6-94.5% and 77.8-91.8% at three different concentrations. The limits of determinations based on S/N=3 were 0.07 ng/g and 0.09 ng/g, which are below the maximum residue limits established in many countries.

• Journal of the Korean Magnetic Resonance Society
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• v.11 no.1
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• pp.10-23
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• 2007

A new disintegrin protein named saxatilin was purified from Korean snake venom (Gloydius saxatilis). Saxatilin is a 73 residue small ploypeptide, which has a primary recognition motif in extracellular matrix, Arg-Gly-Asp (RGD) sequence. Data from inhibition activity assay for the ${\alpha}_v{\beta}_3$ integrin showed that saxatilin showed about 5000-fold higher activity than those of RGD peptides, suggesting that RGD sequence may not be sufficient to induce full cellular function of this site. The solution structures calculated from NMR data were well converged for backbone atoms except RGD loop. The structure revealed that most of tight turns are stabilized by medium range NOE contacts and the RGD motif is located far from the rigid core of the C-terminal domain. The three-dimensional fold and biological function of saxatilin are discussed with those of salmosin, which is a disintegrin protein derived from Agkistrodon halys brevicaudus.

• Korean Journal of Veterinary Service
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• v.29 no.3
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• pp.317-330
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• 2006

This study was conducted to develop the analytical method about simultaneous determination for synthetic antimicrobials in muscle by high performance liquid chromatography - mass selective detector (HPLC- MSD). Solid phase extraction (SPE), matrix solid phase dispersion (MSPD) and liquid-liquid extraction (LLE) have been adapted as pretreatment procedures for HPLC- MSD. Among various solvent tested, methanol was chosen for extraction of synthetic antimicrobials in muscles. For the optimized response, the values of various MS parameters including fragment voltage, drying gas flow, nebulizer pressure, drying gas temperature were verified. The average recovery rates using MSPD and SPE for muscles of bovine and pork were 78.9-127.1% and 78.3-121.7%, respectively. This method was verified the satisfactory performance for fourteen synthetic antimicrobials excepting carbadox in muscle of pork as detection limit of $0.05{\mu}g/g$ on API/ES SIM mode.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1791-1800
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• 2004

Angiotensin I, a model decapeptide, was glycosylated and partially hydrolyzed with HCl (6 N, 80 $^{\circ}C$, 4 h), aminopeptidase, and carboxypeptidase Y. A single peptide mass map obtained from truncated peptides in the partial acid hydrolysate of angiotensin and its glycosylation product mixture by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry enabled sequencing of angiotensin by a combinatorial procedure. MALDI-TOF and electrospray ionization (ESI) tandem mass spectrometric results indicate that both the N-terminal amino group of aspartic acid and the guanidinium group of the second residue arginine are glycosylated.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2224-2228
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• 2012

This study describes the ability of capillary electrochromatography (CEC) for the determination of imidacloprid and carbendazim in tomato samples. A novel liquid crystal crown ether modified hybrid silica monolithic column was synthesized, characterized and developed as separation column for the first time. Baseline separation of imidacloprid and carbendazim could be achieved using a mobile phase containing 90% (v/v) 20 mmol/L phosphate buffer (pH 7.0) and 10% (v/v) acetonitrile. The matrix matched calibration curves were linear with correlation coefficient $r^2$ > 0.9998 in the range of 0.20-10.00 mg/L. The limits of detection for imidacloprid and carbendazim were 0.061 and 0.15 mg/kg, respectively, which were below the maximum residue limits established by the European Union as well as Codex Alimentarius. Average recoveries for imidacloprid and carbendazim varied from 101.6-108.0% with relative standard deviations lower than 6.3%. This method was applied to the analysis of tomatoes collected from local markets.

• Korean Journal of Environmental Agriculture
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• v.37 no.4
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• pp.283-290
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• 2018

BACKGROUND: Pesticide residue analysis is an essential activity in order to establish the food safety of agricultural products. Analytical approaches to the food safety are required to meet internationally the guideline of Codex (Codex Alimentarius Commission, CAC/GL 40). In this study, we developed a liquid chromatograph-tandem mass spectrometer (LC-MS/MS) method to determine the herbicide clopyralid in food matrixes. METHODS AND RESULTS: Clopyralid was extracted with aqueous acetonitrile containing formic acid and the extracts were mixed in a citrate buffer consisted of magnesium sulfate anhydrous, NaCl, sodium citrate dihydrate and disodium hydrogencitrate sesquihydrate followed by centrifugation. The supernatants were filtered through a nylon membrane filter and used for the analysis of clopyralid. The method was validated by accuracy and precision experiments on the samples fortified at 3 different levels of clopyralid. LC-MS/MS in positive mode was employed to quantitatively determine clopyralid in the food samples. Matrix-matched calibration curves were inearranged from 0.001 to 0.25 mg/kg with r2 > 0.994. The limits of detection and quantification were determined to be 0.001 and 0.01 mg/kg, respectively. There covery values of clopyralid for tified at 0.01 mg/kg in the control samples ranged from approximately 82 to 106% with relative standard deviations below 2 0%. CONCLUSION: The method developed in this study meets successfully the Codex guideline for pesticide residue analysis in food samples. This, the method could be applicable to determine pesticides in foods produced domestically and internationally.

• Korean Journal of Environmental Agriculture
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• v.39 no.3
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• pp.246-252
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• 2020

BACKGROUND: Pesticides are broadly used to control weeds and pests, and the residues remaining in crops are managed in accordance with the MRLs (maximum residue limits). Therefore, an analytical method is required to quantify the residues, and we conducted a series of analyses to select and validate the quick and simple analytical method for tolpyralate in five agricultural products using QuEChERS (quick, easy, cheap, effective, rugged and safe) method and LC-MS/MS (liquid chromatography-tandem mass spectrometry). METHODS AND RESULTS: The agricultural samples were extracted with acetonitrile followed by addition of anhydrous magnesium sulfate, sodium chloride, disodium hydrogencitrate sesquihydrate and trisodium citrate dihydrate. After shaking and centrifugation, purification was performed with d-SPE (dispersive-solid phase extraction) sorbents. To validate the optimized method, its selectivity, linearity, LOD (limit of detection), LOQ (limit of quantitation), accuracy, repeatability, and reproducibility from the inter-laboratory analyses were considered. LOQ of the analytical method was 0.01 mg/kg at five agricultural products and the linearity of matrix-matched calibration were good at seven concentration levels, from 0.0025 to 0.25 mg/L (R²≥0.9980). Mean recoveries at three spiking levels (n=5) were in the range of 85.2~112.4% with associated relative standard deviation values less than 6.2%, and the coefficient of variation between the two laboratories was also below 13%. All optimized results were validated according to the criteria ranges requested in the Codex Alimentarius Commission (CAC) and Ministry of Food and Drug Safety (MFDS) guidelines. CONCLUSION: In conclusion, we suggest that the selected and validated method could serve as a basic data for detecting tolpyralate residue in imported and domestic agricultural products.