• Korean Journal of Clinical Laboratory Science
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• v.37 no.1
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• pp.22-26
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• 2005

Total homocysteine is now considered a risk factor for cardiovascular diseases. I increased interest has led to a multitude of studies requiring the determination of total homocysteine in conjunction with other factor. There are various methods for measuring total homocysteine, including HPLC, FPIA, GC-MS and LC-MS/MS. The most recent method for measuring total homocysteine uses a deuterium-labelled internal standard and tandem mass spectrometry. This development requires no derivatization and therefore leads to an increase in sample throughput compared to other techniques. We have evaluated the method for homocysteine by the LC-MS/MS method, and the correlation between the FPIA method and the LC-MS/MS method. The standard curve (0, 5, 10, 20, 50, 100 uM) was linear over the range examined (up to 100 uM). The lower limit of quantification (CV < 10 %) was 0.5 uM/L and the lower limit of detection (S/N >3) was 0.1 uM/L. Intra-assay variation and inter-assay variation were both <6 %. The comparision study for homocysteine concentration showed good correlation (r=0.9684) between the FPIA method and LC-MS/MS methods. Our conclusion is that the method showed relatively good precision, and was rapid and accurate.

• Analytical Science and Technology
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• v.34 no.1
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• pp.1-8
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• 2021

An analytical method was developed and optimized for the quantification of a plant growth regulator, 2,6-diisopropylnaphthalene (2,6-DIPN), in agricultural products using gas chromatography-tandem mass spectrometry. The samples were extracted, partitioned, and were purified using a Florisil® cartridge. To validate the analytical method, its specificity, linearity, limit of detection (LOD) and limit of quantification (LOQ) of the instrument, LOQ of the analytical method (MLOQ), accuracy, and repeatability were considered. The method displayed excellent results during validation, and is suitable for the determination and quantification of the low residual levels of the analyte in the agricultural samples. All of the results with the optimized method were satisfactory and within the criteria ranges requested in the Codex Alimentarius Commission guidelines and the Ministry of Food and Drug Safety guidelines for pesticide residue analysis. The developed method is simple and accurate and can be used as a basis for safety management of 2,6-DIPN.

• Horticultural Science & Technology
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• v.28 no.4
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• pp.672-677
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• 2010

A duplex PCR method was developed to detect a transformation vector pSPB130 used in the development of a genetically modified (GM) rose plant. To detect a GM rose plant, the anthocyanin synthase ($ANS$) was used as an endogenous reference gene of rose in PCR detection. The primer pair RHANS-KF/KR producing 107 bp amplicon was used to amplify the $ANS$ gene and no amplified product was observed in any of the 9 different plants used as a template. The primer pair GMRH-KF/KR was designed to amplify the junction sequence between 35S promoter and flavonoid 3',5'-hydroxylase ($F3^{\prime}5^{\prime}H$) gene in pSPB130. The detection limit of the duplex PCR method is approximately 0.5%. This result indicates that this duplex PCR method could be useful for monitoring unauthorized GM rose in Korea.

• Fisheries and Aquatic Sciences
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• v.23 no.4
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• pp.10.1-10.10
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• 2020

Background: Butaphosphan (BTP) has recently been introduced into the Korean aquaculture sector as a stressattenuating agent. In this study, a sensitive chemical analytical method was established for the detection of BTP in the olive flounder (Paralichthys olivaceus) tissues. Methods: Utilizing a method employing liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), detection sensitivity, specificity, and precision were satisfactorily established. Temporal changes in the BTP plasma and muscle concentrations were assessed after a single intramuscular injection of BTP (50 and 150 mg/kg) to the olive flounder maintained at 13 ℃ or 22 ℃. Results: High BTP plasma levels were achieved immediately after the injection, and the drug was rapidly eliminated. Additionally, plasma BTP levels were markedly dependent on the elimination rate, which, in turn, seemed dependent on the water temperature, with the drug elimination half-life and mean residence time significantly shorter at 22 ℃ than 13 ℃. Overall, muscle BTP levels were markedly lower than the plasma levels. Notably, muscle levels were not influenced by water temperatures. Muscle BTP concentrations were used to estimate the necessary withdrawal period for drugs used in food fish, with BTP levels maintained far below the possible hazardous limit. Conclusions: In conclusion, the established LC-MS/MS method can be used for BTP residue detection with high sensitivity and reproducibility.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.415-422
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• 2021

Cotton is an important fiber crop, and its seeds are used as feed for dairy cattle. Crop biotechnology has been used to improve agronomic traits and quality in the agricultural industry. The frequent unintentional release of LM cotton into the environment in South Korea is attributed to the increased application of living modified (LM) cotton in food, feed, and processing industries. To identify and monitor the LM cotton, a method for detecting the approved LM cotton in South Korea is required. In this study, we developed a method for the simultaneous detection of four LM cotton varieties, MON757, MON88702, COT67B, and GHB811. The genetic information of each LM event was obtained from the European Commission-Joint Research Centre and Animal and Plant Quarantine Agency. We designed event-specific primers to develop a multiplex PCR method for LM cotton and confirmed the specific amplification. Using specificity assay, random reference material(RM) mixture analysis and limit of detection(LOD), we verified the accuracy and specificity of the multiplex PCR method. Our results demonstrate that the method enabled the detection of each event and validation of the specificity using other LM RMs. The efficiency of multiplex PCR was further verified using a random RM mixture. Based on the LOD, the method identified 25 ng of template DNA in a single reaction. In summary, we developed a multiplex PCR method for simultaneous detection of four LM cotton varieties, for possible application in LM volunteer analysis.

• The Korean Journal of Pesticide Science
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• v.19 no.4
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• pp.370-393
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• 2015

This study was conducted to compare STQ method, multi-residue method in Korean food code and QuEChERS method for validated selected and accuracy, reproducibility and efficiency. A total of 45 selected and targeted pesticides were the analyzed by GC and 5 of them were crops (apple, potato, green pepper, rice, soy bean). $R^2$ values were calculated in the standard calibration curve was over 0.990. Recovery tests were performed by three replications in two levels and the relative standard deviation of the repeated experiments was less than 30%. The average percentage of recoveries in the multi-residue method in Korean food code was 89.13%, QuEChERS method was 92.45% and STQ method was 85.28%. In addition, matrix effects in multi-residue method in Korean food code was 24.61%, QuEChERS method was 23.98% and STQ method showed 11.24%. The STQ method is easy and showed high clean-up effect in extracting the sample solution than the QuEChERS method and clean-up with C18, PLS, PSA cartridge columns. A large volume of the sample was injected in order to compensable for the problem, that occurred due to high detection limit in the analyser. When the STQ method was applied using a large volume injector, the standard calibration curve showed a higher linearity $R^2=0.990$, and method detection limit was 0.01 mg/kg. It showed an average recovery of 91.84% and the relative standard deviations of three replications repeated in two level process was less than 30% and had an average matrix effect of 17.90%.

• Journal of Food Hygiene and Safety
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• v.33 no.1
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• pp.58-64
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• 2018

An analytical method for the determination of cephalexin (CEX) in bovine tissues (muscle, liver, kidney and fat tissues) was developed and validated using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Tissue samples were extracted by the liquid-liquid extraction based on 5% trichloroacetic acid (TCA). The chromatographic separation was achieved on a reverse phase $C_{18}$ column with gradient elution using a mobile phase of 20 mM hexafluroacetylacetone (HFAC)/50% acetonitrile (40:60). The procedure was validated according to the Ministry of Food and Drug Safety guideline determining accuracy, precision, and limit of detection. Mean recoveries of CEX from spiked edible tissues ($6{\sim}1,500{\mu}g/kg$) were 83.9~106.8%, and the relative standard deviation was between 2.3 and 14.8%. Linearities were obtained with the correlation coefficient ($r^2$) of > 0.999. Limit of detection and limit of quantification for the investigated CEX were 2~10 and $6{\sim}30{\mu}g/kg$, respectively. This method was reliable, sensitive, economical and suitable for routine monitoring of CEX residues in bovine edible tissues.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.755-761
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• 2017

This study was conducted to establish an analytical method using an HPLC system equipped with a photodiode array (PDA) detector for the quality control of raw materials and cosmeceuticals containing fucoxanthin as an active ingredient. The column was octadecyl-functionalized silica gel and the measurement wavelength of the PDA was set to 499 nm. To validate the analytical method, the linearity of the calibration curve, detection limit, reproducibility and recovery rate were investigated and good results were obtained. The correlation coefficient of the calibration curve was 1.000 and the linearity was good in the concentration range of 0.5 ~ 100 ppm. Moreover, the limit of detection (LOD) was 0.1 ppm and the limit of quantification (LOQ) was 0.5 ppm. The results of the peak reproducibility test used for evaluating the system suitability showed that the RSD (n = 5) of the peak area was 2.0% and that of the retention time was 0.09%. In the spiking test, the recovery rate was $101.6{\pm}0.77%$. The fucoxanthin contents of the two kinds of fucoxanthin-containing raw materials were $49.6{\pm}3.3%$ and $1.03{\pm}0.016%$, respectively. In addition, the fucoxanthin content in the test product, which was intended to be 150 ppm, was $156.7{\pm}4.7ppm$. From the above results, it was concluded that this method could be applied to the quantitative analysis of fucoxanthin in cosmeceuticals.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.19-19
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• 2005

This paper reports a novel magnetic force-based microfluidic immunoassay using microbeads and magnetic nanoparticles. The magnetic force-based immunoassay was devised first and successfully applied to detect the rabbit IgG as the model analyte of microfluidic sandwich immunoassay. The microchannels were fabricated by poly(dimethysiloxane) (PDMS) molding processes and bonded on a slide glass by plasma treatment. At the part of the inlet, sample solution was hydrodynamically focused. The focused microbeads of sample solution were flowed through the 150 ${\mu}m$ width channel of outlet. However, when the microbeads are conjugated with the superparamagnetic nanoparticles under the applied magnetic fields, they will switch their flow path and flow through the 95 ${\mu}m$ width channel of outlet. The movements of microbeads conjugated with magnetic nanoparticles were demonstrated by magnetic field $gradients.^{1)}$ High magnetic field gradients using micro electromagnets could be applied to this detection method for high sensitivity and lower detection limit. In addition, the multiplexed $immunoassay^{2)}$ using an encoded microbead which is immobilized with a certain antibody could be possible using this detection principle.

• Journal of Food Hygiene and Safety
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• v.12 no.2
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• pp.117-124
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• 1997

A simple, rapid and simultaneous analytical method is described for the detection of Sulfonamide and Tetracycline residues, i.e., Sulfamerazine (SMR), Sulfamethazine (SMT), Sulfamonomethoxine (SMM), Sulfadimethoxine (SDM), Sulfaquinoxaline (SQN), Oxytetracycline (OXY), Tetracycline (TC), Chlortetracycline (CTC). Blank control and sulfonamide and tetracycline fortified fish muscle samples (0.5 f) were blended with octadecylsilyl (C18, 40 ${\mu}{\textrm}{m}$, 21% load, 60$\AA$) derivatized silica packing material (2 g). Blended fish samples were washed with hexane, then, benzene and dichloromethace were used for the elution of tetracycline and sulfonamide were analyzed by HPLC. Correlation coefficients of standard curves for individual sulfonamide and tetracycline isolated from fortified samples were linear (0.9993$\pm$0.0003~0.9997$\pm$0.0003, 0.9493$\pm$0.078~0.9753$\pm$0.036), respectively. The average percentage recoveries of sulfonamide and tetracycline ranged as 80.86~96.52% to 85.88~92.23%, and 30.01~37.12% to 65.89~73.40%, for the concentration range (0.1~1.0 ppm) examined, respectively. Limit of detection for sulfonamide was 0.0012 ppm for SMR in Paralichthys Olivacleus and 0.0020 ppm for SMR, 0.015 ppm for SMM in Cyprinus Carpio. The applicability of this procedure is demonstrated by separation and detection of incurred tetracycline and sulfonamide residues in fish muscle tissue.