• Mass Spectrometry Letters
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• v.10 no.3
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• pp.88-92
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• 2019

A sensitive analytical method of rhodanthpyrone A in rat plasma was developed using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Rhodanthpyrone A and rhodanthpyrone B (internal standard) in rat plasma were extracted by a liquid-liquid extraction method with ethyl acetate. This extraction method gave results in high and reproducible extraction recovery in the range of 73.75-79.90% with no interfering peaks around the peak elution time of rhodanthpyrone A and B. The standard calibration curves for rhodanthpyrone A ranged from 0.5 to 2000 ng/mL were linear with $r^2$ > 0.994 and the inter- and intra-day accuracy and precision and the stability were within acceptance criteria. Using this validated analytical method, pharmacokinetics of rhodanthpyrone A following intravenous and oral administration of rhodanthpyrone A at doses of 2 mg/kg and 30 mg/kg, respectively, were investigated. Rhodanthpyrone A in rat plasma showed multi-exponential elimination pattern with high clearance and volume of distribution values. The absolute oral bioavailability of this compound was calculated as 3.7%. Collectively, the newly developed sensitive LC-MS/MS analytical method of rhodanthpyrone A could be successfully applied to investigate the pharmacokinetic properties of this compound and would be useful for the further studies on the efficacy, toxicity, and biopharmaceutics of rhodanthpyrone A.

• Analytical Science and Technology
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• v.30 no.2
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• pp.102-111
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• 2017

Here we reported a methodology for identification of triacylglycerols (TAGs) and diacylglycerols (DAGs) in coix seed by preparative thin layer chromatography (prep-TLC) and non-aqueous reversed-phase liquid chromatography (NARP LC)-atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS/MS). Lipid components were extracted from coix seed by reflux extraction using n-hexane for 3 hr. TAGs and DAGs in coix seed extract were effectively purified and isolated from matrix interferences by prep-TLC and then analyzed by LC-APCI-MS and MS/MS for identification. TAGs were effectively identified taking into consideration of their LC retention behavior, APCI-MS spectra patterns, and MS/MS spectra of $[DAG]^+$ ions. In MS/MS spectra of TAGs, diacylglycerol-like fragment $[DAG]^+$ ions were useful to identify TAGs with isobaric fragment ions. Based on an established method, 27 TAGs and 8 DAGs were identified in coix seed extract. Among them, 15 TAGs and 8 DAGs were for the first time observed in coix seed. Interestingly, some of TAGs isolated by prep-TLC were partly converted into DAGs through probably photolysis process during storing in room temperature. Thus, degradation phenomenon of TAGs should be considered in the quality evaluation and nutritional property of coix seed. LC-APCI-MS/MS combined with prep-TLC will be practical method for precise TAG and DAG analysis of other herbal plants.

• Journal of the Korean Chemical Society
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• v.59 no.3
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• pp.225-232
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• 2015

A liquid chromatography-electrospray ionization-tandem mass spectrometry method (LC-ESI-MS/MS) was used for determining seven pesticides (2,4-dichlorophenoxyacetic acid, methomyl, aldicarb, 2-methyl- 4-chlorophenoxy- acetic acid, molinate, carbaryl and carbofuran) and two synthetic materials (quinoline and bisphenol-A) in surface water. The analytes were extracted using solid-phase extraction (SPE). The eluate was concentrated by nitrogen gas. 100 microliters of 30% (v/v) methanol aqueous solution were used to dissolve the residue and an aliquot of the reconstituted solution was directly injected into LC-ESI-MS/MS after the filtration using 0.2 μm polytetrafluoroethylene (PTFE) syringe filter. Under the established condition, the calibration curves of the analytes were linear with correlation coefficients of above 0.997. The quantification limit was 0.002~0.011 μg/L and the relative standard deviations were less than 16.4%. In addition, accuracy was in the range of 84~107% and the recoveries were values between 56.2 and 98.6%. In this study, the developed method was applied to the analysis of real surface water samples.

• Bulletin of the Korean Chemical Society
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• v.26 no.5
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• pp.729-734
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• 2005

A sensitive and selective method for quantitation of sofalcone and its active metabolite in human plasma has been established using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS). Plasma samples were transferred into 96-well plate using an automated sample handling system and spiked with 10 $\mu$L of 2 $\mu$g/mL $d_3$-sofalcone and $d_3$-sofalcone metabolite solutions (internal standard), respectively. After adding 0.5 mL of acetonitrile to the 96-well plate, the plasma samples were then vortexed for 30 sec. After centrifugation, the supernatant was transferred into another 96-well plate and completely evaporated at 40 ${^{\circ}C}$ under a stream of nitrogen. Dry residues were reconstituted with mobile phase and were injected into a $C_{18}$ reversed-phase column. The limit of quantitation of sofalcone and its metabolite was 2 ng/mL, using a sample volume of 0.2 mL for analysis. The reproducibility of the method was evaluated by analyzing 10 replicates over the concentration range of 2 ng/mL to 1000 ng/mL. The validation experiments of the method have shown that the assay has good precision and accuracy. Sofalcone and its metabolite produced a protonated precursor ion ([M+H]$^+$) of m/z 451 and 453, and a corresponding product ion of m/z 315 and 317, respectively. Internal standard ($d_3$-sofalcone and $d_3$-sofalcone metabolite) produced a protonated precursor ion ([M+H]$^+$) of m/z 454 and 456 and a corresponding product ion of m/z 315 and 317, respectively. The method has been successfully applied to a pharmacokinetic study of sofalcone and its active metabolite in human plasma.

• Food Science of Animal Resources
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• v.35 no.6
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• pp.765-771
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• 2015

The development of a sample preparation method and optimization of the analytical instrumentation conditions were performed for the determination of the vitamin B₁₂ content in emulsified baby foods sold on the Korea market. After removal of the milk protein and fats by chloroform extraction and centrifugation, the vitamin B₁₂ was water extracted from the sample. Following filtration of the solution through a nylon filter, the water-soluble extract was purified by solid-phase extraction using a Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS). The solution eluted from the cartridge was dried under a stream of nitrogen gas and reconstituted with 1 mL of water. The sample solution was injected into an LC-MS/MS system after optimizing the mobile phase for vitamin B₁₂ detection. The calibration curve showed good linearity with the coefficient of correlation (r²) value of 0.9999. The limit of detection was 0.03 µg/L and the limit of quantitation was 0.1 µg/L. The method of detection limit was 0.02 µg/kg. The vitamin B₁₂ recovery from a spiking test was 99.62% for infant formula and 99.46% for cereal-based baby food. The sample preparation method developed in this study would be appropriate for the rapid determination of the vitamin B₁₂ content in infant formula and baby foods with emulsified milk characteristics. The ability to obtain stable results more quickly and efficiently would also allow governments to exercise a more extensive quality control inspection and monitoring of products expected to contain vitamin B₁₂. This method could be implemented in laboratories that require time and labor saving.

• Journal of Food Hygiene and Safety
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• v.32 no.2
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• pp.89-95
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• 2017

A rapid, sensitive analytical method for glucuronolactone in beverages was developed and validated using hydrophilic interaction liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HILIC-ESI-MS/MS). To determine the optimum analytical conditions for glucuronolactone, three different kinds of HILIC columns and two mobile phases with different pH values were examined. An amide-bonded stationary phase with a pH 9 acetonitrile-rich mobile phase was the best condition in terms of column retention, ESI-MS/MS response area, and signal-to-noise ratio. After extraction, glucuronolactone was separated through the HILIC amide column and detected by negative ESI-MS/MS in selected reaction monitoring (SRM) mode. Nine energy drinks sold in Korea were spiked with glucuronolactone at a concentration of 5 ng/mL; the Monster $Energy^{TM}$ sample showed the smallest peak area and its signal-to-noise ratio was used for method validation. Good linearity was obtained in the concentration range from 20 to 1500 ng/mL with a correlation coefficient > 0.998. The developed method had a limit of detection (LOD) of 6 ng/mL and a limit of quantitation (LOQ) of 20 ng/mL. The recovery of this method at concentration of 20, 100, 500, and 1000 ng/mL was 96.3%-99.2% with relative standard deviations (RSD) of 1.6%-14.0%. A reproducibility precision assessment at concentration of 100 and 500 ng/mL was carried out among three laboratories. The recovery of that evaluation was 95.1%-102.3% with RSD of 2.7%-7.0%. An analysis of variance indicated that there was no difference between the recovery results of the three laboratories at the 5% significance level. The validated method is applicable to inspecting beverages adulterated with glucuronolactone in Korea.

• Translational and Clinical Pharmacology
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• v.25 no.2
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• pp.67-73
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• 2017

Glimepiride, a third generation sulfonylurea, is an antihyperglycemic agent widely used to treat type 2 diabetes mellitus. In this study, an untargeted urinary metabolomic analysis was performed to identify endogenous metabolites affected by glimepiride administration. Urine samples of twelve healthy male volunteers were collected before and after administration of 2 mg glimepiride. These samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and then subjected to multivariate data analysis including principal component analysis and orthogonal partial least squares discriminant analysis. Through this metabolomic profiling, we identified several endogenous metabolites such as adenosine 3', 5'-cyclic monophosphate (cAMP), quercetin, tyramine, and urocanic acid, which exhibit significant metabolomic changes between pre- and posturine samples. Among these, cAMP, which is known to be related to insulin secretion, was the most significantly altered metabolite following glimepiride administration. In addition, the pathway analysis showed that purine, tyrosine, and histidine metabolism was affected by pharmacological responses to glimepiride. Together, the results suggest that the pharmacometabolomic approach, based on LC-MS/MS, is useful in understanding the alterations in biochemical pathways associated with glimepiride action.

• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.745-750
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• 2007

An isotope dilution-liquid chromatography/tandem mass spectrometric method was developed as a candidate reference method for the accurate determination of folic acid in infant milk formula. Sample was spiked with 13C5-folic acid and then extracted with phosphate buffer (pH 6) solution. The extract was further cleaned up by deproteinization followed by a C18 solid-phase extraction cartridge. The extract was analyzed by using LC/ ESI/MS/MS with selectively monitoring the collisionally induced dissociation channels of m/z 442 → m/z 295 and m/z 447 → m/z 295, which are the neutral glutamyl loss from the [M+H]+ ions of folic acid and 13C5-folic acid, respectively. LC/MS/MS chromatograms showed substantially reduced background from chemical noises compared to LC/MS chromatograms. Repeatability and reproducibility studies showed that the LC/MS/ MS method is a reliable and reproducible method which can provide less than 1.5 relative percentage of method precision.

• Analytical Science and Technology
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• v.15 no.5
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• pp.410-416
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• 2002

In this study, a new quantitative analytical method has been developed for the rapid determination of vancomycin in human plasma and urine using liquid chromatography/tandem mass spectrometry (LC - MS/MS). Chromatography was carried out on a $C_{18}$ XTerra MS column ($2.1{\times}30mm$) with a particle size of $3.5{\mu}m$. The mobile phase was 0.25% formic acid in 10% acetonitrile and the flow rate was $250{\mu}L/min$. Vancomycin and caffeine (internal standard) were detected by MS/MS using multiple reaction monitoring (MRM). Vancomycin gives a predominant doubly protonated precursor molecule ($[M+2H]^{2+}$) at m/z 725.0 and a corresponding product ion of m/z 100.0. Detection of vancomycin was good, accurate and precise, with a limit of detection of 1 nM in plasma. The calibration curves for vancomycin in human plasma was linear in a concentration range of $0.01{\mu}M$ - $100{\mu}M$ for plasma. This method has been successfully applied to determine the concentration of vancomycin in human plasma and urine from pharmacokinetic study and relative studies.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.288-309
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• 2022

BACKGROUND: The objective of this study was to develop a comprehensive and simple method for the simultaneous determination of 59 veterinary drug residues in livestock products for safety management. METHODS AND RESULTS: For sample preparation, we used a modified liquid extraction method, according to which the sample was extracted with 80% acetonitrile followed by incubation at -20℃ for 30 min. After centrifugation, an aliquot of the extract was evaporated to dryness at 40℃ and analyzed using liquid chromatography combined with tandem mass spectrometry. The method was validated at three concentration levels for beef, pork, chicken, egg, and milk in accordance with the Codex Alimentarius Commission/Guidelines 71-2009. Quantitative analysis was performed using a matrix-matched calibration. As a results, at least 52 (77.6%) out of 66 compounds showed the proper method validation results in terms of both recovery of the target compound and coefficient of variation required by Codex guidelines in livestock products. The limit of quantitation of the method ranged from 0.2 to 1119.6 ng g-1 for all matrices. CONCLUSION(S): This method was accurate, effective, and comprehensive for 59 veterinary drugs determination in livestock products, and can be used to investigate veterinary drugs from different chemical families for safety management in livestock products.