• Proceedings of the PSK Conference
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• 2003.10b
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• pp.223.2-223.2
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• 2003

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric (LC/MS/MS) method for the determination of eupatilin in human plasma was developed. Eupatilin and internal standard, (S)-[N-3-(4-(2-(1-methyl-5-tetrazolyl)-pyridine-5-y1)- 3-fluorophenyl)-2-oxo-5-oxazolidinyl]methyl acetamide (DA-7867) were extracted from human plasma by liquid-liquid extraction and analyzed on a phenyl-hexyl column with the mobile phase of acetonitrile-ammonium formate (10 mM, pH 3.0) (60:40, v/v). (omitted)

• Proceedings of the Korean Vacuum Society Conference
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• 2003.02a
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• pp.205-205
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• 2003

• The Korean Journal of Physiology and Pharmacology
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• v.16 no.5
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• pp.355-360
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• 2012

A simple, sensitive and reproducible high-performance liquid chromatography (HPLC) method has been validated for determining concentrations of glutamate, glycine, and alanine in human plasma. Proteins in plasma were precipitated with perchloric acid, followed by derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC). Simultaneous analysis of glutamate, glycine, and alanine is achieved using reversed-phase HPLC conditions and ultraviolet detection. Excellent linearity was observed for these three amino acids over their concentration ranges with correlation coefficients (r)>0.999. The intra- and inter-day precision were below 10%. This method utilizes quality control samples and demonstrates excellent plasma recovery and accuracy. The developed method has been successfully applied to measure plasma glutamate, glycine, and alanine in twenty volunteers.

• Journal of Ginseng Research
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• v.43 no.4
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• pp.539-549
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• 2019

Background: 20(S)-Protopanaxadiol (PPD), the aglycone part of 20(S)-protopanaxadiol ginsenosides, possesses antidepressant activity among many other pharmacological activities. It is currently undergoing clinical trial in China as an antidepressant. Methods: In this study, an ultra-performance liquid chromatography coupled with triple quadrupole time-of-flight mass tandem mass spectrometry method was established to identify the metabolites of PPD in human plasma and urine following oral administration in phase IIa clinical trial. Results: A total of 40 metabolites in human plasma and urine were identified using this method. Four metabolites identified were isolated from rat feces, and two of them were analyzed by NMR to elucidate the exact structures. The structures of isolated compounds were confirmed as (20S,24S)-epoxydammarane-12,23,25-triol-3-one and (20S,24S)-epoxydammarane-3,12,23,25-tetrol. Both compounds were found as metabolites in human for the first time. Upon comparing our findings with the findings of the in vitro study of PPD metabolism in human liver microsomes and human hepatocytes, metabolites with m/z 475.3783 and phase II metabolites were not found in our study whereas metabolites with m/z 505.3530, 523.3641, and 525.3788 were exclusively detected in our experiments. Conclusion: The metabolites identified using ultra-performance liquid chromatography coupled with triple quadrupole time-of-flight mass spectrometry in our study were mostly hydroxylated metabolites. This indicated that PPD was metabolized in human body mainly through phase I hepatic metabolism. The main metabolites are in 20,24-oxide form with multiple hydroxylation sites. Finally, the metabolic pathways of PPD in vivo (human) were proposed based on structural analysis.

• Journal of Pharmaceutical Investigation
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• v.37 no.3
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• pp.179-186
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• 2007

A simple, sensitive and selective liquid chromatographic/tandem mass spectrometric method (LC-MS/MS) was developed and validated for doxifluridine and 5-fluorouracil (5-FU) quantification in dog heparinized plasma. Sample preparation was based on liquid-liquid extraction using a mixture of isopropanol/ethyl acetate (1/9 v/v) to extract doxifluridine, 5-FU and 5-chlorouracil (5-CU, an internal standard) from plasma. Chromatography was performed on a C-18 analytical column and the retention times were 2.7, 1.5 and 1.7 min for doxifluridine, 5-FU and 5-CU, respectively with shorter analysis time within 5 min than previously reported methods. The ionization was optimized using ESI negative mode and selectivity was achieved by tandem mass spectrometric analysis by multiple reaction monitoring (MRM) using the transformations of m/z 244.8>107.6, 129.0>42.0 and 144.9>42.1 for doxifluridine, 5-FU and 5-CU, respectively. The achieved low limit of quantification was 20.0 ng/mL and the assay exhibited linear range of 20-2000 ng/mL ($R^2>0.99957$ for doxifluridine and $R^2>0.99857$ for 5-FU), using $100{\mu}L$ of plasma. Accuracy and precision of quality control samples for both doxifluridine and 5-FU met KFDA and FDA Guidance criteria of 15% for accuracy with coefficients of variation less than 15%. This method demonstrated adequate sensitivity, specificity, accuracy, precision and stability to support the simultaneous analysis of doxifluridine and 5-FU in dog plasma samples in pharmacokinetic and bioequivalence studies.

• Annals of Laboratory Medicine
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• v.38 no.6
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• pp.518-523
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• 2018

Background: Lipemia, a significant source of analytical errors in clinical laboratory settings, should be removed prior to measuring biochemical parameters. We investigated whether lipemia in serum/plasma samples can be removed using a method that is easier and more practicable than ultracentrifugation, the current reference method. Methods: Seven hospital laboratories in Spain participated in this study. We first compared the effectiveness of ultracentrifugation ($108,200{\times}g$) and high-speed centrifugation ($10,000{\times}g$ for 15 minutes) in removing lipemia. Second, we compared high-speed centrifugation with two liquid-liquid extraction methods-LipoClear (StatSpin, Norwood, USA), and 1,1,2-trichlorotrifluoroethane (Merck, Darmstadt, Germany). We assessed 14 biochemical parameters: serum/plasma concentrations of sodium ion, potassium ion, chloride ion, glucose, total protein, albumin, creatinine, urea, alkaline phosphatase, gamma-glutamyl transferase, alanine aminotransferase, aspartate-aminotransferase, calcium, and bilirubin. We analyzed whether the differences between lipemia removal methods exceeded the limit for clinically significant interference (LCSI). Results: When ultracentrifugation and high-speed centrifugation were compared, no parameter had a difference that exceeded the LCSI. When high-speed centrifugation was compared with the two liquid-liquid extraction methods, we found differences exceeding the LCSI in protein, calcium, and aspartate aminotransferase in the comparison with 1,1,2-trichlorotrifluoroethane, and in protein, albumin, and calcium in the comparison with LipoClear. Differences in other parameters did not exceed the LCSI. Conclusions: High-speed centrifugation ($10,000{\times}g$ for 15 minutes) can be used instead of ultracentrifugation to remove lipemia in serum/plasma samples. LipoClear and 1,1,2-trichlorotrifluoroethane are unsuitable as they interfere with the measurement of certain parameters.

• Journal of the Korean Ceramic Society
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• v.45 no.7
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• pp.380-386
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• 2008

Optimized volume production of nanoscale phosphor powders synthesized by radio frequency (RF) plasma process was developed for the application to plasma display panels. The nano powders were synthesized by feeding the both solid and liquid type precursors, and nanoparticle phosphors were characterized in terms of particle size, shape, and photoluminescence (PL) intensities. Computer simulation was performed in advance to determine the process parameters, and nano phosphors were evaluated by comparing with current commercial micron-sized phosphor powders. Practical feeding of both solid and liquid type precursor was proved to be effective for volume production.The developed process showed a potential as a production method for red, blue and green phosphor although the PL intensity still needs further improvement.

• Mass Spectrometry Letters
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• v.12 no.1
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• pp.21-25
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• 2021

We aimed to develop and validate a sensitive analytical method of nannozinone A, active metabolite of Nannochelins A extracted from the Myxobacterium Nannocytis pusilla, in mouse plasma using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Mouse plasma samples containing nannozinone A and 13C-caffeine (internal standard) were extracted using a liquid-liquid extraction (LLE) method with methyl tert-butyl ether. Standard calibration curves were linear in the concentration range of 1 - 1000 ng/mL (r2 > 0.998) with the inter- and intra-day accuracy and precision results less than 15%. LLE method gave results in the high and reproducible extraction recovery in the range of 78.00-81.08% with limited matrix effect in the range of 70.56-96.49%. The pharmacokinetics of nannozinone A after intravenous injection (5 mg/kg) and oral administration (30 mg/kg) of nannozinone A were investigated using the validated LC-MS/MS analysis of nannozinone A. The absolute oral bioavailability of nannozinone A was 8.82%. Plasma concentration of nannozinone A after the intravenous injection sharply decreased for 4 h but plasma concentration of orally administered nannozinone A showed fast distribution and slow elimination for 24 h. In conclusion, we successfully applied this newly developed sensitive LC-MS/MS analytical method of nannozinone A to the pharmacokinetic evaluation of this compound. This method can be useful for further studies on the pharmacokinetic optimization and evaluating the druggability of nannozinone A including its efficacy and toxicity.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1571-1574
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• 2013

• Mass Spectrometry Letters
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• v.13 no.4
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• pp.158-165
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• 2022

Many therapeutic class drugs such as beta-blocker, corticosteroids, NSAIDs, etc are prohibited substances in the horse racing industry. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology makes it possible to isolate drugs from interference, enables various drug analyses in complex biological samples due to its sensitive sensitivity, and has been successfully applied to doping control. In this paper, we describe a rapid and sensitive method based on solid-phase extraction (SPE) using solid phase cartridge and LC-MS/MS to screen for different class's 35 drug targets in equine plasma. Plasma samples were pretreated by SPE with the NEXUS cartridge consisted non-polar carbon resin and minimum buffer solvent. Chromatographic separation of the analytes was performed on ACQUITY HSS C18 column (2.1 × 150 mm, 1.8 ㎛). The elution gradient was conducted with 5 mM ammonium formate (pH 3.0) in distilled water and 0.1% formic acid in acetonitrile at a flow rate of 0.25 mL/min. The selected reaction monitoring (SRM) mode was used for drug screening with multiple transitions in the positive ionization mode. The specificity, limit of detection, recovery, and stability was evaluated for validation. The method was found to be sensitive and reproducible for drug screening. The method was applied to plasma sample analysis for the proficiency test from the Association of Racing Chemist.