• Korean Journal of Food Science and Technology
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• v.44 no.2
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• pp.247-250
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• 2012

Raw milk samples (n=28) obtained from milk tanks in 3 dairy plants of different regions and commercial milks (n=100) were collected from six cities. These samples were analyzed for the level of aflatoxin $M_1$ contamination using immunoaffinity columns and high performance liquid chromatography coupled with fluorescent detectors. Confirmation of aflatoxin $M_1$ ($AFM_1$) identified in positive samples was based on the formation of the hemiacetal derivative ($AFM_{2a}$) after derivatization with trifluroacetic acid. The average concentrations of aflatoxin $M_1$ in the raw milks were 25.1 ng/kg, and those values in commercial milks were 29.8 ng/kg. The highest level of aflatoxin $M_1$ in milk was 72.7 ng/kg. These results showed that the contamination of aflatoxin $M_1$ in milks consumed in the Korea was quite low compared to the standard in Korea Food Code (aflatoxin $M_1$ 500 ng/kg).

• Journal of the Korean Chemical Society
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• v.41 no.4
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• pp.186-197
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• 1997

Estrogens, which play an important role in sex hormone and potential inhibitor of cancer cell proliferation were profiled for normal female and male. The nineteen endogeneous estrogens were simultaneously analyzed by selected ion monitoring method of GC/MS. Urinary estrogens were extracted by using Serdolit AD-2 resin, hydrolyzed with $\beta-glucuronidase/arylsulfatase$ from Helix pomatia, liquid-liquid extraction and quantitatively derivatized by MSTFA/TMSCl mixture in order to be detected on the GC/MS. The good quality-control data were obtained through the precision and accuracy test and the recovery range of them was 80.97∼97.81%. The Korean reference values of urinary estrogens were established and differences were found in normal female compared with normal male.

• Toxicological Research
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• v.26 no.2
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• pp.149-155
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• 2010

The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with ${\mu}$-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and $11.1{\mu}g/l$, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to $250{\mu}g/l$. The intra- and inter-day accuracy (n = 6) ranged from 89.2% to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples.

• Korean Journal of Environmental Agriculture
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• v.40 no.2
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• pp.99-107
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• 2021

BACKGROUND: Pesticide uptake by a rotational crop after being used for the primary crop is a potential cause of violation against the pesticide law if the pesticide is not registered in the secondary crop. This study was conducted to investigate the plant back interval (PBI) of fluopyram for the rotational cultivation of radish. METHODS AND RESULTS: Two experimental approaches were performed the evaluation of residues in radish cultivated successively in soil 16 days after treated with fluopyram onto pepper plant (T1) and in radish cultivated in bare soil treated with fluopyram at PBI 30 and PBI 60 days (T2). A modified QuEChERS method coupled with LC/MS/MS analysis showed good linearity of matrix-matched standard calibration of fluopyram with the coefficient values of determination greater than 0.995. Recovery values at levels of 0.01, 0.05, 0.1 and 0.25 mg/kg ranged from average 84.9 to 117.6% with RSD less than 10%. Fluopyram residues in radish harvested from T1 and T2 were found as levels less than maximum residue limit. CONCLUSION: This study suggests 20~30 days as the PBI of fluopyram for the rotational cultivation of radish in the greenhouse soil treated with fluopyram used for pepper as the primary crop.

• Analytical Science and Technology
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• v.25 no.1
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• pp.25-32
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• 2012

Isotope dilution mass spectrometry (ID-MS) based on liquid chromatography tandem mass spectrometry (LC/MS/MS) was developed for the accurate determination of sorbic acid in tea-drink. An isotope analogue of sorbic acid, $^{13}C_2$-sorbic acid, was obtained by custom synthesis. MS was operated in the negative mode with selected reaction monitoring (SRM) mode of $[M-H]^-$ ${\rightarrow}$ $[M-CO_2H]^-$ channel at m/z 111 ${\rightarrow}$ 67 for sorbic acid and at m/z 113 ${\rightarrow}$ 68 for its isotope analogue. Chromatographic separation was accomplished with a C18 column and an isocratic mobile phase of 55% of 50 mM ammonium acetate (pH 4.5) and 45% of methanol. Homogeneous reference materials were prepared for validation of this method, including repeatability and reproducibility tests, by fortifying tea-drink with sorbic acid in our laboratory. Repeatability and reproducibility studies showed that the ID-LC/MS method is a reliable and reproducible method which provides less than 3.8% of relative standard deviation (RSD) for the analysis of sorbic acid.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.5
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• pp.646-652
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• 2017

The aim of this study was to investigate method validation for determination of sesamol, sesamin, and sesamolin in non-fermented sesame and fermented sesame by bioconversion. For validation, the specificity, linearity, precision, accuracy, limits of detection (LOD), and quantification (LOQ) of sesamol, sesamin, and sesamolin were measured by HPLC. Linearity tests showed that the coefficients of calibration correlation ($R^2$) for sesamol, sesamin, and sesamolin were 0.9999. Recovery rates of lignan contents in non-fermented and fermented sesame were high in the ranges of 100.27~115.10% and 98.43~114.90%, respectively. The inter-day and intra-day precisions of sesamin and sesamolin analyses for non-fermented and fermented sesame were 0.27~1.94% and 0.25~0.69%, respectively. The LOD and LOQ were $0.23{\sim}0.34{\mu}g/g$ and $0.70{\sim}1.03{\mu}g/g$, respectively. These results indicate that the validated method is appropriate for the determination of sesamol, sesamin, and sesamolin.

• Journal of the Korean Chemical Society
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• v.54 no.5
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• pp.556-566
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• 2010

A new kinetic spectrophotometric method is developed for the measurement of Mn(II) in natural water samples. The method is based on the catalytic effect of Mn(II) with the oxidation of Gallocyanin by $KIO_4$ using nitrilotriacetic acid (NTA) as an activation reagent at 620 nm. The optimum conditions obtained are $4.00{\times}1^{-5}\;M$ Gallocyanin, $KIO_4$, $1.00{\times}10^{-4}\;M$ NTA, 0.1 M HAc/NaAc buffer of pH = 3.50, the reaction time of 5 min and the temperature of $30^{\circ}C$. Under the optimum conditions, the proposed method allows the measurement of Mn(II) in a range of $0.1\;-\;4.0\;ng\;mL^{-1}$ and with a detection limit of down to $0.025\;ng\;mL^{-1}$. The recovery efficiency in measuring the standard Mn(II) solution is in a range of 98.5 - 102%, and the RSD is in a range of 0.76 - 1.25%. The newly developed kinetic method has been successfully applied to the measurement of Mn(II) in both some environmental water samples and certified standard reference river water sample, JAC-0031 with satisfying results. Moreover, few cations and anions interfere with the measurement of Mn(II). Compared with the other catalytic-kinetic methods and instrumental methods, the proposed kinetic method shows fairly good selectivity and sensitivity, low cost, cheapness, low detection limit and rapidity. It can easily and successfully be applied to the real water samples with relatively low salt content and complex matrices such as bottled drinking water, cold and hot spring waters, lake water, river water samples.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.11
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• pp.1737-1741
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• 2014

An HPLC method for determination of naringin was developed to standardize it as a marker compound in Goheung yuzu extract as a functional health food. Optimum results were obtained by C-18 column chromatography using solvent mixtures (A: 0.5% acetic acid, B: acetonitrile) as the stationary phase and mobile phase. The method was fully validated and sensitive with a limit of detection (LOD) of 0.0218 mg/L and limit of quantification (LOQ) of 0.0661 mg/L. The method showed high linearity (coefficient of correlation=0.9986) and high accuracy, as recovery rates of naringin at concentrations of 1, 0.5, 0.1, 0.05 mg/mL were in the ranges of 95.74~98.25%, 97.67~101.01%, 97.33~104.64%, and 95.53~106.82%, respectively. Intra-day and inter-day variation, which are measures of method precision, were 1.39~1.95% and 0.17~1.49%, respectively. Therefore, the method could be used without modification for determination of naringin as a marker compound in Goheung yuzu extracts.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.1
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• pp.33-41
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• 2012

An effective, environmentally friendly analytic methods using gas chromatography with mass spectrometric detector (GC-MSD) have been developed for the quantitative analysis of trace phthalate levels in cosmetics such as nail lacquer and hair spray. Since such cosmetics are largely comprised of organic solvents, conventional clean-up methods that have been widely used for phthalate analyses are in adequate. In addition, analysis of trace phthalate levels is notorious for its sensitivity to contamination, which causes high analytical values. A direct sample dilution method using an organic solvent was adopted to the sample preparation process to determine the exact amounts of phthalates and simultaneously avoid the high risk of secondary contamination. The method has many advantages including high accuracy, sensitivity, and simplicity in sample preparation. Dibutyl phthalate (DBP) and di (2-ethylhexyl) phthalate (DEHP) were selected for analysis because they have been frequently detected in cosmetics and consistently reported as endocrine disruptors in humans and animals. Internal standard method using two deuterium substitutes (DBP-$d_4$, DEHP-$d_4$) as the internal standard was also used. The results of 'Method validation' showed the capabilities of this method for the routine analysis of phthalates at the ppm level. The recovery ranges were between 95 % and 106.1 %, and relative standards deviations (RSD) were less than 3.9 % in fortified nail lacquer and hair spray samples at the concentration of $25{\mu}g/g$.

• Analytical Science and Technology
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• v.25 no.5
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• pp.307-312
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• 2012

To perform inhalation toxicity test by using experiment animals, we set up an analytical method to monitor didecyldimethylammonium chloride (DDAC) in aerosol nebulized into inhalation chambers by ion chromatography. DDAC was adsorbed by XAD-2 resin and analyzed with conductivity detector. Recovery of DDAC desorbed by acetonitrile from XAD adsorbent was 87.8%. The method detection limit (MDL) and the limit of quantitation (LOQ) were 2.97 ${\mu}g/m^3$ and 8.92 ${\mu}g/m^3$, respectively. Repeatability was calculated as RSD 7.8% in the range of 0~20 ${\mu}g/mL$. Time needed to analyze a sample was less than 5 minutes. Therefore, the analysis of DDAC by ion chromatography was practically useful in monitoring DDAC in inhalation chambers with rapidity and sensitivity manner to perform inhalation toxicity test using experimental animals.