• Bulletin of the Korean Chemical Society
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• v.28 no.5
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• pp.737-744
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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 acrylamide in potato chips, starch-rich foodstuff cooked at high temperature. Sample was spiked with 13C3-acrylamide and then extracted with water. The extract was further cleaned up with an Oasis HLB solid-phase extraction (SPE) cartridge and an Oasis mixed-phase cation exchange (MCX) SPE cartridge. The extract was analyzed by using LC/ESI/Tandem MS in positive ion mode. LC with a medium reversed-phase (C4) column was optimized to obtain adequate chromatographic retention and separation of acrylamide. MS was operated to selectively monitor [M+H]+ ions of the analyte and its isotope analogue at m/z 72 and m/z 75, respectively. Sample was also analyzed by the LC/MS with selectively monitoring the collisionally induced dissociation channels of m/z 72 → m/z 55 and m/z 75 → 58. Compared to the LC/MS chromatograms, the LC/MS/MS chromatograms showed substantially reduced background chemical noises coming from solvent clusters formed during ESI spray processes and interferences from sample matrix. Repeatability and reproducibility studies showed that the LC/MS/MS method is a reliable and reproducible method which can provide a typical method precision of 1.0% while the LC/MS results are influenced by chemical interferences.

• Mass Spectrometry Letters
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• v.8 no.4
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• pp.109-113
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• 2017

Single analytical procedure including extraction, liquid chromatography, and mass spectrometric analysis was evaluated for the simultaneous measurement of lysophospholipids (LPLs). LPLs, particularly, lysophosphatidic acids (LPA) and sphingosine 1-phosphate (S1P) are lipid messengers ubiquitously found in various biological matrix. The molecular species mediate important physiological roles in association with many diseases (e.g. cancer, inflammation, and neurodegenerative disease), which emphasize the significance of the simple and reliable analytical method for biomarker discovery and molecular mechanistic understanding. Thus, we developed analytical method mainly focusing on, but not limited by those lipid species S1P and LPA using reverse phase liquid chromatography-tandem mass spectrometry (RPLC-ESI-MS-MS). Extraction method was modified based on Folch method with optimally minimal level of ionization additive (ammonium formate 10 mM and formic acid). Reverse-phase liquid-chromatography was applied for chromatographical separation in combination with negative ionization mode electrospray-coupled Orbitrap mass spectrometry. The method validation was performed on human blood plasma in a non-targeted lipid profiling manner with full-scan MS mode and data-dependent MS/MS. The proposed method presented good inter-assay precision for primary targets, S1P and LPA. Subsequent analysis of other types of LPLs identified a broad range of lysophosphatidylcholines (LPCs) and lysophosphatidyl-ethanolamines (LPEs).

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.821-827
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• 2014

An isotope dilution liquid chromatography tandem mass spectrometry (ID LC-MS/MS) method has been developed and applied to the determination of arsenobetaine (AsB, ${(CH_3)_3}^+AsCH_2COO^-$) from oyster candidate certified reference material (CRM). The exact matching isotope dilution approach was adopted for accurate determination of AsB using $^{13}C_2$-labeled AsB as an internal standard. Efficiencies of different AsB extraction methods were evaluated using a codfish reference material and a simple sonication method was selected as the method of choice for the certification of the oyster candidate CRM. The hydrophilic interaction liquid chromatography (HILIC) combined with electrospray ionization tandem mass spectrometry (ESI/MS/MS) in selected reaction monitoring (SRM) mode was optimized for adequate chromatographic retention and robust quantification of AsB from codfish and oyster samples. By analyzing 12 subsamples taken from each 12 bottles systematically selected from the whole oyster CRM batch, the certified value of AsB was determined as $6.60mg{\cdot}kg^{-1}{\pm}0.31mg{\cdot}kg^{-1}$ and it showed excellent between-bottle homogeneity of less than 0.42%, which is represented by relative standard deviation of 12 bottles from the CRM batch. The major source of uncertainty was the certified value of the AsB standard solution.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.649-669
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• 2016

This study explored the analytical conditions for 21 veterinary antibiotics which have been popularly sold in South Korea in 2014 but have not yet been targeted in EPA method 1694. Most of the selected antibiotics were separated by a reverse-phase C18 column with a combination of (buffered) water and organic polar solvent, which was commonly methanol and acetonitrile in the gradient elution mode. Volatile additives such as formic acid, ammonium acetate and ammonium formate were usually added to the mobile phases to minimize asymmetrical and tailing of antibiotics' peaks and to increase their ionization in mass spectrometry. The analytical methods of aminoglycoside antibiotics were distinct from those of the other antibiotics in terms of adoption of ion-pair chromatography (IPC) and hydrophilic interaction liquid chromatography (HILIC) capable of retaining and separating extremely polar compounds due to their hydrophilicity. Trifluoroacetic acid or heptafluorobutyric acid was frequently added to the mobile phase as an ion-pair reagent for the IPC. Tandem mass spectrometry was numerously applied to the detection of antibiotics using positive electrospray ionization (ESI) and the selected reaction monitoring (SRM) mode. All reviewed analytical methods had been/were validated by evaluating recovery, limits of detection and quantification, decision limit or detection capability of the methods.

• Korean Journal of Pharmacognosy
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• v.48 no.4
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• pp.320-328
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• 2017

Yongdamsagan-tang has been used to treat the urinary disorders, acute- and chronic-urethritis, and cystitis in Korea. In this study, an ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS/MS) method was established for simultaneous analysis of the 20 bioactive marker compounds, geniposidic acid, chlorogenic acid, geniposide, liquiritin apioside, acteoside, calceolarioside B, liquiritin, nodakenin, baicalin, liquiritigenin, wogonoside, baicalein, glycyrrhizin, wogonin, glycyrrhizin, wogonin, saikosaponin A, decursin, decursinol angelate, alisol B, alisol B acetate, and pachymic acid in traditional herbal formula, Yongdamsagan-tang. Chromatographic separations of all marker compounds were conducted using a Waters Acquity UPLC BEH $C_{18}$ analytical column ($2.1{\times}100mm$, $1.7{\mu}m$) at $45^{\circ}C$ using a mobile phase of 0.1% (v/v) formic acid in water and acetonitrile with gradient elution. The MS analysis was performed using a Waters ACQUITY TQD LC-MS/MS coupled with an electrospray ionization source in the positive and negative modes. The flow rate was 0.3 mL/min and injection volume was $2.0{\mu}L$. The correlation coefficient of 20 marker compounds in the test ranges was 0.9943-1.0000. The limits of detection and quantification values of the all marker components were 0.11-6.66 and 0.34-19.99 ng/mL, respectively. As a result of the analysis using the optimized LC-ESI-MS/MS method, three compounds, geniposidic acid (from Plantaginis Semen), alisol B (from Alismatis Rhizoma), and pachymic acid (from Poria Sclerotium), were not detected in this sample. While the amounts of the 17 compounds except for the geniposidic acid, alisol B, and pachymic acid were $0.04-548.13{\mu}g/g$ in Yongdamsagan-tang sample. Among these compounds, baicalin, bioactive marker compound of Scutellariae Radix, was detected at the highest amount as a $548.13{\mu}g/g$.

• Korean Journal of Pharmacognosy
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• v.47 no.1
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• pp.92-101
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• 2016

In this study, an ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS/MS) method was established for simultaneous determination of the 25 marker components, including chlorogenic acid, gallic acid, oxypaeoniflorin, homogentisic acid, methyl gallate, caffeic acid, 3,4-dihydroxybenzaldehyde, paeoniflorin, albiflorin, liquiritin, nodakenin, ferulic acid, ginsenoside Rg1, liquiritigenin, coumarin, cinnamic acid, benzoylpaeoniflorin, ginsenoside Rb1, cinnamaldehyde, paeonol, glycyrrhizin, 6-gingerol, evodiamine, rutecarpine, and spicatoside A in traditional Korean formula, Onkyung-tang. All analytes were separated on a Waters Acquity UPLC BEH $C_{18}$ analytical column ($2.1{\times}100mm$, $1.7{\mu}m$) at $45^{\circ}C$ using a mobile phase of 0.1% (v/v) formic acid in water and acetonitrile with gradient elution. The MS analysis was carried out using a Waters ACQUITY TQD LC-MS/MS coupled with an electrospray ionization (ESI) source in the positive and negative modes. The flow rate and injection volume were 0.3 mL/min and $2.0{\mu}L$, respectively. The correlation coefficient of all analytes in the test ranges was greater than 0.98. The limits of detection and quantification values of the 25 marker compounds were in the ranges 0.03-19.43 and 0.09-58.29 ng/mL, respectively. As a result, methyl gallate, 3,4-dihydroxybenzaldehyde, evodiamine, and rutecarpine were not detected in this sample and the concentrations of the 21 compounds except for the above 4 compounds were $33.09-3,496.32{\mu}g/g$ in Onkyung-tang decoction. Among these compounds, paeonol was detected at the highest amount as a $3,496.32{\mu}g/g$.

• Mass Spectrometry Letters
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• v.14 no.4
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• pp.153-159
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• 2023

The copper ion, Cu(II), binding sites for amyloid fragment Aβ1-16 (=Aβ16 ) were investigated to explain the biological activity difference in the Aβ16 aggregation process. The [M+Cu+(z-2)H]^z+ (z = 2, 3 and 4, M = Aβ16 monomer) and [D+Cu+(z-2)H]^z+ (z = 3 and 5, D = Aβ16 dimer) structures were investigated using electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Fragment ions of the [M+Cu+(z-2)H]^z+ and [D+Cu+(z-2)H]^z+ complexes were observed using collision-induced dissociation MS/MS. Three different fragmentation patterns (fragment "a", "b", and "y" ion series) were observed in the MS/MS spectrum of the (Aβ16 monomer or dimer-Cu) complex, with the "b" and "y" ion series regularly observed. The "a" ion series was not observed in the MS/MS spectrum of the [M+Cu+2H]⁴⁺ complex. In the non-covalent bond dissociation process, the [D+Cu+3H]⁵⁺ complex separated into three components ([M+Cu+H]³⁺, M³⁺, and M²⁺), and the [M+Cu]²⁺ subunit was not observed. The {M + fragment ion of [M+Cu+H]³⁺} fragmentation pattern was observed during the covalent bond dissociation of the [D+Cu +3H]⁵⁺ complex. The {M + [M+Cu+H]³⁺} complex geometry was assumed to be stable in the [D+Cu+3H]⁵⁺ complex. The {M + fragment ion of [M+Cu]²⁺} fragmentation pattern was also observed in the MS/MS spectrum of the [D+Cu+H]³⁺ complex. The {M + [y₉+Cu]¹⁺} fragment ion was the characteristic fragment ion. The [D+Cu+H]³⁺ and [D+Cu+3H]⁵⁺ complexes were likely to form a monomer-monomer-Cu (M-M-Cu) structure instead of a monomer-Cu-monomer (M-Cu-M) structure.

• Journal of Microbiology and Biotechnology
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• v.16 no.1
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• pp.25-31
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• 2006

Changes of CP4 5-enolpyruvylshikimate-3-phosphate synthase (CP4 EPSPS) in the glyphosate-tolerant Roundup Ready soybean were examined using purified CP4 EPSPS produced in cloned Escherichia coli as a control. CP4 EPSPS in genetically modified soybean was detected by twodimensional gel electrophoresis (2-DE) and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS) with databases. CP4 EPSPS in soybean products was resolved on 2-DE by first isoelectric focusing (IEF) based on its characteristic pI of 5.1, followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) based on its molecular mass of 47.5 kDa. We quantified various percentages of soybean CP4 EPSPS. The quantitative analysis was performed using a 2D software program on artificial gels with spots varying in Gaussian volumes. These results suggested that 2-DE image analysis could be used for quantitative detection of GM soybean, unlike Western blotting.

• Analytical Science and Technology
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• v.25 no.6
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• pp.435-440
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• 2012

A liquid chromatography-electrospray ionization-tandem mass spectrometry method (LC-ESI-MS/MS) was used for determining perchlorate in the Gum-River surface water. Sample was directly injected into LC-ESI-MS/MS after the filtrations using PTFE filter paper. The coefficient of variation of perchlorate was less than 3% and the limit of quantification was 0.17 ${\mu}g/L$. Water samples were collected from thirty-five basins of Gum-River on February, April and June 2012, respectively. As a result, perchlorate was detected in the concentration range of 0.23-3.73 ${\mu}g/L$ (mean 0.20 ${\mu}g/L$) in the frequency of 15% in general surface water and in the concentration range of 0.36-25.10 ${\mu}g/L$ (mean 1.69 ${\mu}g/L$) in the frequency of 36% in surface water samples near industry area.

• 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.