• Journal of People, Plants, and Environment
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• v.21 no.6
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• pp.485-492
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• 2018

This study aimed to develop and validate highly sensitive determination method of a prostaglandin ($PGE_1$, OP 1206) in human plasma by LC-MS/MS using column switching. Plasma stored at $-30^{\circ}C$ and treated with methanol effectively inhibited interferences synthesized post-sampling. Samples were added with internal standard and were separated by reversed-phase HPLC with a cycle time of 30min. The method was selective for OP 1206 and the regression models, based on internal standard, were linear across the concentration range 0.5-50 pg/mL with the limit of quantification of 0.5 pg/mL (limit of quantitation, LOQ) for OP 1206. The calibration curve of OP 1206 standards spiked in five individual plasma samples was linear ($r^2=0.9999$). Accuracy and precision at the concentrations of 0.5, 1.5, 5.0 and 40 pg/mL, and at the lower LOQ of 0.5 pg/mL were excellent at 20%. OP120 < 6 was stable in plasma samples for at least 24 hours at room temperature, 24 hours frozen at $-70^{\circ}C$, 24 hours in an auto sampler at $6^{\circ}C$, and for two freeze/unfreezing cycles. The validated determination method successfully quantified the concentrations of OP 1206 in plasma samples from simulated administrating a single $5{\mu}g$ OP 1206 formulation. Thus, this novel LC-MS/MS technique for drug separation, detection and quantitation is expected to become the standard highly-sensitive detection method in bioanalysis and to be applied to many low dose pharmaceutical products.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.6
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• pp.559-572
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• 2018

The aim of this study was to evaluate pretreatment methods for 27 pharmaceuticals and personal care products (PPCPs) in various sewage samples using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) and online solid-phase extraction with LC-MS/MS. Extraction efficiencies of PPCPs in the solid phase under different experimental conditions were evaluated, showing that the highest recoveries were obtained with the addition of sodium sulfate and ethylenediaminetetraacetic acid disodium salt dehydrate in acidified conditions. The recoveries of target compounds ranged from 91 to 117.2% for liquid samples and from 61.3 to 137.2% for solid samples, with a good precision. The methods under development were applied to sewage samples collected in two sewage treatment plants (STPs) to determine PPCPs in liquid and solid phases. Out of 27 PPCPs, more than 19 compounds were detected in liquid samples (i.e., influent and effluent) of two STPs, with concentration ranges of LOQ-33,152 ng/L in influents and LOQ-4,523 ng/L in effluents, respectively. In addition, some PPCPs such as acetylsalicylic acid, ibuprofen, and ofloxacin were detected at high concentrations in activated sludge as well as in excess sludge. This methodology was successfully applied to sewage samples for the determination of the target compounds in STPs.

• Natural Product Sciences
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• v.25 no.1
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• pp.49-58
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• 2019

Eleven steroid hormones (SHs: androstene-3,17-dione, estrone, ${\beta}$-estradiol, ${\alpha}$-estradiol, testosterone, dehydroepiandrosterone, $17{\acute{a}}$-hydroxyprogesterone, medroxyprogesterone, megestrol acetate, progesterone, and androsterone) were detected from New Zealand deer (Cervus elaphus var. scoticus) velvet antler (NZA, 鹿茸 ). A method for the quantification of eleven SHs was established by using ultraperformance liquid chromatography (UPLC)-MS/MS. The linearities ($R^2$ > 0.991), limits of quantification (LOQ values, 0.3 ng/mL to 23.1 ng/mL), intraday and interday precisions (relative standard deviation: RSD < 2.43%), and recovery rates (97.3% to 104.6%) for all eleven SHs were determined. In addition, a method for the quantification of three 7-oxycholesterols (7-O-CSs: 7-ketocholesterol, $7{\alpha}$-hydroxycholesterol, and $7{\beta}$-hydroxycholesterol) in the NZA was established by using an HPLC-photodiode array (PDA) method. The linearities ($R^2$ > 0.999), LOQ values (30 ng/mL to 350 ng/mL), intraday and interday precisions (RSD < 1.93%), and recovery rates (97.2% to 103.5%) for the three 7-O-CSs were determined. These quantitative methods are accurate, precise, and reproducible. As a result, it is suggested that the five steroid compounds of androstene-3,17-dione, androsterone, 7-ketocholesterol, $7{\alpha}$-hydroxycholesterol, and $7{\beta}$-hydroxycholesterol could be marker steroids of NZA. These methods can be applied to quantify or standardize the marker steroids present in NZA.

• 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.

• Korean Journal of Environmental Agriculture
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• v.41 no.3
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• pp.153-157
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• 2022

BACKGROUND: The residue dissipation pattern of pesticides for agricultural products during the pre-harvest period after the final application is important to prevent the maximum residue limit (MRL) violations in domestic and export markets. The MRL violations of carbendazim are observed more often in chamnamul by pesticide residue management surveys by the Ministry of Food and Drug Safety. The residue level at the pre-harvest interval (PHI) and the residue dissipation constant from the critical good agricultural practice (cGAP) trials could be estimated to meet the MRL and pose a health risk to consumers. METHODS AND RESULTS: Chamnamuls were harvested at 0, 1, 3, 5, 7, 10, and 14 days after application of carbendazim in accordance with critical GAP. The residue analysis in chamnanul was performed by HPLC-DAD with the C₁₈ column. The limit of quantitation of carbendazim was 0.04 mg/kg, and the recoveries were 74.4 - 95.8% at the two spiked levels (LOQ and 10LOQ) of carbendazim. The dissipation rates in chamnamul were calculated from the residues at the sampling days by statistical method at a 95% confidence level. The biological half-lives of residual carbendazim in the field trials 1 and 2 were 4.9 and 4.4 days, respectively. CONCLUSION(S): In this dissipation study, the residue concentrations at the recommended PHI were higher than the established MRL in Korea. Therefore, the MRL is proposed based on the residue data sets from the trials conducted at the same cGAP and the dietary exposure assessment.

• Korean Journal of Environmental Agriculture
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• v.41 no.3
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• pp.206-216
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• 2022

BACKGROUND: Dithiocarbamate fungicide propineb can be analyzed quantitatively by derivatization reaction followed by HPLC/UVD, which has high reproducibility and stability. However, the presence of high protein in soybeans and peas affects the derivatization process resulting in extremely low recoveries. Therefore, this study was conducted to improve the analytical method for analysis of propineb in soybeans and peas by applying a deproteinization process using chloroform-gel method. METHODS AND RESULTS: The deproteinization process was carried out up to 6 times for soybeans and 5 times for peas using 50 mL chloroform. After 4 times of deproteinization process followed by a derivatization reaction with methyl iodide, the recovery yields of propineb in both pulses were >90%. However, the recovery yield tended to decrease when the deproteinization process was performed more than 5 times. The method limit of quantification (LOQ) was 0.04 mg/L. The recovery conducted in triplicate at 10 times and 50 times of the LOQ ranged from 87.2 to 95.0 % with a coefficient of variation <10%. CONCLUSION(S): This study confirmed that 4 times of deproteinization process using the chloroform-gel method was effective when derivatizing and analyzing dithiocarbamate fungicides in pulses with high protein content. However, depending on the initial protein content present in the pulses, there was a difference in the recovery: the lower the protein content, the higher the recovery rate of propineb. It is expected that the method proposed in this study could be applied to remove high content of protein as analytical interference substance from agricultural samples.

• The Korea Journal of Herbology
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• v.29 no.1
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• pp.13-18
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• 2014

Objectives : Iridoid glycoside, swertiamarin is a well known bioactive component found in Swertia japonica Makino (SJ). In this study, we tried to optimize a suitable method which would extract swertiamarin effectively. Methods : Extraction of SJ was carried out by various conditions of time (5 - 60 min), temperature ($30-70^{\circ}C$), solvent (from non-polar to polar), and ratio of solvnet / sample (10 : 1 - 40 : 1) using ultrasonic extractor. Swertiamarin in SJ extracts was quantified by high performance liquid chromatography - Phtodiode array detector (HPLC-PDA) using C18 column and the analytical procedure was validated by evaluation of specificity, range, linearity, accuracy (recovery), precision (intra- and inter day variability), limit of detection (LOD), and limit of quantification (LOQ). Results : An efficient extraction condition for swertiamarin in SJ was optimized using sonicator extraction (temperature $40^{\circ}C$, solvent 20% methanol, solvent / sample (20 : 1), and time 10 min. Analytical procedure was optimized by HPLC-PDA using isocratic solvent system of acetonitrile and water (9 : 91), and the method was validated in regard to linearity (correlation coefficient, $R^2$ > 0.9999), range ($50-1000{\mu}g/mL$), intra- and inter-precision (RSD < 5.0 %), and recovery (99 -103 %). LOD and LOQ were 0.051 and $0.155{\mu}g/mL$, respectively. Conclusion : An optimized method of extraction for swertiamarin in SJ was established through conditions of diverse extraction and the validation result indicated that the method is suited for the determination of swertiamarin in SJ.

• Mass Spectrometry Letters
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• v.13 no.3
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• pp.58-83
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• 2022

We developed analytical methods using high performance chromatography (HPLC) and liquid chromatography tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of 80 unapproved compounds in dietary supplements. The target compounds for analysis were unapproved ingredients (e.g., pharmaceuticals) that have potential adverse effects on consumers owing to accidental misuse, overuse, and interaction with other medication in dietary supplement. Two analytical methods were tested to identify the optimal validation results according to AOAC guideline. As a result, limit of quantification (LOQ) was 0.14-0.5 ㎍ mL^-1; linearity (r²) was ≥ 0.99; accuracy (expressed as recovery) was 78.9-114%; precision (relative standard deviation) was ≤ 4.28% in the HPLC method. In the LC-MS/MS method, LOQ was 0.01-2 ng mL^-1, linearity (r²) was ≥0.98, accuracy was 71.7-119%; precision was ≤ 12.5%. The developed methods were applied to 51 dietary supplements collected from 2019 to 2021 through MFDS alert system. Based on our previous monitoring study, major compounds were icariin, sibutramine, yohimbine, sildenafil, tadalafil, sennosides (A, B), cascarosides (A, B, C, D), and phenolphthalein. In this study, we re-analyzed samples of detected compounds, and evaluated the statistical difference using Bland-Altman analysis to compare two analytical approaches between HPLC and LC-MS/MS. These results showed a good agreement between two methods that can be used to monitor the unapproved ingredients in dietary supplements. The developed two methods are complementarily suitable for monitoring the adulteration of 80 unapproved compounds in dietary supplements.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.4
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• pp.428-437
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• 2023

A simultaneous analytical method was developed and validated for the analysis of prohibited fluoroquinolone (FQ) antibiotics including norfloxacin, ofloxacin, and pefloxacin, released by aquaculture in seawater and effluents. The samples were filtered, and extracts were obtained using a solid phase extraction cartridge with methanol (MeOH). The extracts were concentrated, and analyzed using ultra-performance liquid chromatography-tandem mass spectrometry. Two different columns and four different mobile phases were compared to achieve optimal separation and sensitivity for target compounds. Typical validation parameters including linearity, recovery of surrogate standard, instrument detection limit (IDL), limit of quantification (LOQ), and method detection limit (MDL) were evaluated. The linearity of calibration curves was over 0.999. Recoveries of surrogate ranged from 87.6% to 113%. The LOQ of target compounds was approximately 3-8 times lower than those reported in previous studies. The IDL and MDL were 0.06-0.57 and 0.06-0.37 ng/L, respectively. Seven effluent samples collected from an aquaculture located in Jeju were analyzed; however, not all target compounds were detected in the samples, suggesting that the banned antibiotics were not used. Overall, this established method was able to simultaneously analyze the three FQ antibiotics, and may be useful for monitoring prohibited antibiotics in the fishery industry.

• Korean Journal of Environmental Agriculture
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• v.42 no.3
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• pp.220-230
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• 2023

Imidacloprid is a neonicotinoid insecticide widely used for insect control in a variety of crops. The evaluation of imidacloprid total residues in animal feeds derived from crop by-products is required to ensure the safety of livestock products. We performed simultaneous LC/MS/MS analyses of imidacloprid and its metabolites in five different livestock products including beef, pork, chicken, milk and egg from domestic markets. The methods for sample preparation and instrumental analysis were established by modifying QuEChERS method to meet the Codex guidelines. The methods generated 0.0035 mg/kg of the limit of determination (LOD), 0.01 mg/kg of the limit of quantitation (LOQ) and standard calibration linearity with >0.983 of the coefficients of determination (R²). The methods exhibited the recovery values of imidacloprid and its metabolites ranging from 65.66 to 119.27% without any interference between matrices. Imidacloprid total residues in the livestock products were found as values lower than the LOQ and maximum residue limits (MRLs). This study suggests that the methods are successfully applicable for the safety evaluation of imidacloprid total residues in livestock products from domestic markets.