• Analytical Science and Technology
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• v.20 no.5
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• pp.424-433
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• 2007

An analytical method for the determination of thyroid hormones in plasma samples has been studied by solid-phase extraction and high-performance liquid chromatography/diode array detector (DAD)/electrospray ionization (ESI)-mass spectrometer. Seven thyroid hormones were successfully separated by gradient elution on the reverse phase Hypersil ODS column (4.6 mm I.D., 250 mm length, particle size $5{\mu}m$) with ammonium formate buffer and acetonitrile. In addition, these compounds were confirmed by UV spectra and ESI-mass Spectra. The extraction recoveries of thyroid hormones in the plasma sample (at pH 3) were in the range of 74.5-115.7 % with solid-phase extraction by C18, followed by elution with 4 mL of methanol. The calibration curves showed good linearity with the correlation coefficients ($r^2$) varying from 0.9939 to 0.9978 and the detection limits of all analytes were obtained in the range of 20-50 ng/mL (38.1-162.8 pmol/mL). As a result, thyroxine was found in the range of 50.98-112.97 ng/mL in normal plasma samples.

• Analytical Science and Technology
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• v.20 no.4
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• pp.331-338
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• 2007

Licorice, Glycyrrhizae Radix is widely used as a herbal medicines and a dietary supplements in East Asia. We employed high performance liquid chromatography electrospray ionization tandem mass spectrometry to determine liquiritin and glycyrrhizin in the Glycyrrhizae Radix. Liquiritin and glycyrrhizin in Glycyrrhizae Radix were ionized by positive ion pneumatically assisted electrospray and detected by HPLC-MS/MS in the multiple-reaction monitoring (MRM) mode using precursor ${\rightarrow}$ product ion combinations at m/z $436.2{\rightarrow}257.0$ and $823.4{\rightarrow}453.4$, respectively. The assay had a calibration range from 10 to 3,000 ng/mL. The limits of detection (LOD) of the liquiritin and glycyrrhizin were 0.4 ng/mL and 0.01 ng/mL, respectively. The reproducibility and repeatability (relative standard deviation) at different analyte concentrations varied from 103 to 113 % and 0.95 to 1.8 %, respectively. According to the above results, HPLC-MS/MS method permits assignment of tentative structures such as liquiritin and glycyrrhizin in the Glycyrrhizae Radix.

• Journal of Ginseng Research
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• v.48 no.5
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• pp.474-480
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• 2024

Background: Recent years have witnessed increasing interest in the high amount of ocotillol-type saponin in Panax vietnamensis, particularly in relation to majonoside R2 (MR2). This unique 3%-5% MR2 content impart Ngoc Linh and Lai Chau ginsengs with unique pharmacological activities. However, in the commercial domain, unauthentic species have infiltrated and significantly hindered access to the authentic, efficacious variety. Thus, suitable analytical techniques for distinguishing authentic Vietnamese ginseng species from others is becoming increasingly crucial. Therefore, MR2 is attracting considerable attention as a target requiring effective management measures. Methods: An enzyme-linked immunosorbent assay (ELISA) was developed by producing monoclonal antibodies against MR2 (mAb 16E11). The method was thoroughly validated, and the potential of the immunoassay was confirmed by high-performance liquid chromatography with ultraviolet spectroscopy. Furthermore, ELISA was applied to the assessment of the MR2 concentrations of various Panax spp., including Korean, American, and Japanese ginsengs. Results and conclusions: An icELISA using mAb 16E11 exhibited linearity between 3.91 and 250 ng/mL of MR2, with detection and quantification limits of 1.53 and 2.50 - 46.6 ng/mL, respectively. Based on this study, the developed icELISA using mAb 16E11 could be a valuable tool for analyzing MR2 level to distinguish authentic Ngoc Linh and Lai Chau ginsengs from unauthentic ones. Furthermore, the analysis of the samples demonstrated that Ngoc Linh and Lai Chau ginsengs exhibit a notably higher MR2 value than all other Panax spp. Thus, MR2 might be their ideal marker compound, and various bioactivities of this species should be explored.

• Analytical Science and Technology
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• v.29 no.2
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• pp.94-103
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• 2016

An analytical method was developed to determine the amount of spinetoram (spinetoram J and spinetoram L) in livestock samples. The spinetoram was extracted with acetonitrile and purified through a primary secondary amine (PSA) sorbent. The spinetoram residues were then quantified and confirmed using a liquid chromatography–tandem mass spectrometer (LC-MS/MS) in the positive ion mode using multiple reactions monitoring (MRM). Matrix-matched calibration curves were linear over the calibration ranges (0.005-0.5 mg/kg) into a blank extract with r² > 0.994. The limits of detection and quantification were 0.002 and 0.01 mg/kg, respectively. The recovery results of spinetram ranged between 81.9-106.4% at different concentration levels (LOQ, 10LOQ, 50LOQ, n=5) with relative standard deviations (RSDs) less than 10%. All values were consistent with the criteria ranges requested in the Codex guidelines (CAC/GL40, 2003). An interlaboratory study was conducted to validate the method. The proposed analytical method proved to be accurate, effective, and sensitive for spinetoram determination. The method will be used as an official analytical method in Korea.

• Journal of Food Hygiene and Safety
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• v.28 no.1
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• pp.63-68
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• 2013

Ethyl carbamate (EC) is a contaminant generated in the fermentation processes of various fermented foods. In this study, residue levels of EC in 95 alcoholic beverage samples were determined by using Gas Chromatography/Tandem Mass Spectrometry (GC/MS/MS). All the samples were purified by a liquid-liquid extraction (LLE) method using dichloromethane. The LLE method enables an improvement in time and cost to detection and specificity over the conventional extraction methods. The limits of detection and quantification (LOD and LOQ) to analyze EC were 1.3 and 4.0 ng/mL, respectively. The recovery rates of EC were ranged from 90.0 to 97.5% at the levels of 50, 100, and 500 ug/L. Among traditional grain-based alcoholic beverage samples (n = 34), the average residue levels of EC in takju, yakju, and cheongju were 0.63, 7.01, and 14.11 ug/L, respectively. Among fruit-based alcoholic beverage samples (n = 48), those of EC in japanese apricot spirits, bokbunjaju, grape wines, and other fruit wines were 79.18, 1.66, 2.64, and 2.39 ug/L, respectively. Among distilled or diluted alcoholic beverage samples (n = 13), those of EC in soju (distilled or diluted), general distillates, liquors, and brandies were 0, 3.30, 8.20, and 8.52 ug/L, respectively. Therefore, this study reports that the residue levels of EC in the alcoholic beverages, distributed in the current domestic markets, did not reach its maximum allowed levels of 30 and 400 ug/L established for grape and fruit wines in Canada, respectively.

• Journal of Food Hygiene and Safety
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• v.26 no.2
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• pp.142-149
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• 2011

An isocratic high performance liquid chromatography (HPLC) method for routine analysis of deoxynivalenol in noodles was validated and estimated the measurement uncertainty. Noodles (dried noodle and ramyeon) were analyzed by HPLC-ultraviolet detection using immunoaffinity column for clean-up. The limits of detection (LOD) and quantification (LOQ) were 7.5 ${\mu}g$/kg and 18.8 ${\mu}g$/kg, respectively. The calibration curve showed a good linearity, with correlation coefficients $r^2$ of 0.9999 in the concentration range from 20 to 500 ${\mu}g$/kg. Recoveries and Repeatabilities expressed as coefficients of variation (CV) spiked with 200 and 500 ${\mu}g$/kg were $82{\pm}2.7%$ and $87{\pm}1.3%$% in dried noodle, and $97{\pm}1.6%$ and $91{\pm}12.0%$ in ramyeon, respectively. The uncertainty sources in measurement process were identified as sample weight, final volume, and sample concentration in extraction volume as well as components such as standard stock solution, working standard solution, 5 standard solutions, calibration curve, matrix, and instrument. Deoxynivalenol concentration and expanded uncertainty in two matrixes spiked with 200 ${\mu}g$/kg and 500 ${\mu}g$/kg were estimated to be $163.8{\pm}52.1$ and $435.2{\pm}91.6\;{\mu}g$/kg for dried noodle, and $194.3{\pm}33.0$ and $453.2{\pm}91.1\;{\mu}g$/kg for ramyeon using a coverage factor of two which gives a level of statistical confidence with approximately 95%. The most influential component among uncertainty sources was the recovery of matrix, followed by calibration curve.

• The Korean Journal of Pesticide Science
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• v.19 no.2
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• pp.81-87
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• 2015

The present study was aimed to predict the pre-harvest residue limits (PHRLs) of pyrimethanil (fungicide) and methoxyfenozide (insecticide) in grape, and to estimate their biological half-lives and residual characteristics. The pesticides were sprayed once on grape in two different fields 10 days before harvest. At the end of 0, 1, 2, 3, 5, 7 and 10 days after application, samples were harvested for further analysis. The residual pesticides were extracted with acetonitrile and partitioned with dichloromethane, and the high-performance liquid chromatography with diode array detector (HPLC/DAD) was employed for the residue analysis. The results obtained in the present study show that the limit of detection of both pesticides were found to be $0.01mg\;kg^{-1}$. The recoveries of these pesticides were ranged between 80.6% and 102.5% with coefficient of variation lower than 10%. The biological half-lives of both pesticides were observed in field 1 and field 2 which shows 7.7 and 7.4 days for pyrimethanil and 5.1 and 6.1 days for methoxyfenozide, respectively. Further, the PHRL of pyrimethanil and methoxyfenozide was found to be $8.90mg\;kg^{-1}$ and $5.51mg\;kg^{-1}$, respectively at 10 days before harvest. Consequently, the present study suggests that the residual amounts of both pesticides will be lower than the maximum residue limits (MRLs) when grape is harvested.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.493-499
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• 2017

This study was conducted to monitor the current status of pesticide residues and sulfur dioxide in a total of 91 functional rice products from February to October 2016. Multi class pesticide multiresidue methods of 220 pesticides was performed by the GC/ECD, GC/NPD, GC/TOF/MS, LC/PDA, and LC/FLD. As a result of analysis, the pesticides were detected in 3 samples, representing a detection rate of 3.3%. The kind of pesticides was propiconazole and isoprothiolane used for germicide in agriculture or plant growth regulator purposes. The detected levels were 0.0340~0.0566 mg/kg, which were under the MRL (Maximum Residues Limits). The contents of sulfur dioxide in 91 samples by the Monier-Williams method were not detected. Risk assessment of pesticides evaluated using human health exposure with the ratio of EDI (Estimated daily intake) to ADI (Acceptable daily intake). %ADI (the ratios of EDI to ADI) were 0.24~1.25% with safety level.

• Analytical Science and Technology
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• v.27 no.5
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• pp.234-242
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• 2014

Imicyafos which is a nematicide for controlling root-knot nematodes has been registered in the Republic of Korea in 2012, and the maximum residue limits of imicyafos are set to watermelon and korean melon as each 0.05 mg/kg. Extremely reliable and sensitive analytical method is required for ensuring food safety on imicyafos residues in agricultural commodities. Imicyafos residues in samples were extracted with acetone, partitioned with hexane and dichloromethane, and then purified with florisil. The purified samples were analyzed by HPLC-UVD and confirmed with LC-MS. Linear range was between 0.1~5 mg/kg with the correlation coefficient ($r^2$) 0.99997. Average recoveries of imicyafos ranged from 77.0 to 115.4% at the spiked levels of 0.02 and 0.05 mg/kg with the relative standard deviations of 2.2~9.6%. Limit of detection and quantification were 0.005 and 0.02 mg/kg, respectively. An inter-laboratory study was conducted to validate the determination method in depth, and the results were satisfactory. All of the validation results revealed that the developed analytical method in this study is relevant for imicyafos determination in agricultural commodities and will be used as an official analytical method.

• The Korean Journal of Pesticide Science
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• v.19 no.3
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• pp.210-217
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• 2015

Ipfencarbazone is a herbicide of the tetrazolinone class, and is believed to be an inhibitor of very long chain fatty acids (VLCFAs), which control cell division in weeds. The objective of this study was to develop and validate an official analytical method for ipfencarbazone determination in agricultural products. The ipfencarbazone residues in agricultural products were extracted with acetone, partitioned with n-hexane, and then purified through silica SPE cartridge. Finally, the analyte was quantified by gas chromatograph-electron capture detector (GC-ECD) and confirmed with gas chromatograph/mass spectrometer(GC/MS). The linear range of ipfencarbazone was 0.01 to 1.0 mg/L with the coefficient of determination ($r^2$) of 0.9999. The limit of detection (LOD) and quantification (LOQ) was 0.003 and 0.01 mg/kg, respectively. In addition, average recoveries of ipfencarbazone ranged from 80.6% to 112.3% at the different concentration levels LOQ, 10LOQ and 50LOQ, while the relative standard deviation was 2.2-8.6%. All values were consistent with the criteria ranges requested in the CODEX guidelines. Furthermore, and inter-laboratory study was conducted to validate the method. This proposed method for determination of ipfencarbazone residues in agricultural products can be used as an official analytical method.