• Mass Spectrometry Letters
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• 제5권4호
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• pp.104-109
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• 2014

Nonmedical use of prescription stimulants such as methylphenidate (MPH) and amphetamine (AP) by normal persons has been increased to improve cognitive functions. Due to high potential for their abuse, reliable analytical methods were required to detect these prescription stimulants in biological samples. A direct injection liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and implemented for simultaneous determination of MPH, AP and their metabolites ritalinic acid (RA) and 4-hydroxyamphetamine (HAP) in human urine. Urine sample was centrifuged and the upper layer ($100{\mu}L$) was mixed with $800{\mu}L$ of distilled water and $100{\mu}L$ of internal standards ($0.2{\mu}g/mL$ in methanol). The mixture was then directly injected into the LC-MS/MS system. The mobile phase was composed of 0.2% formic acid in distilled water (A) and acetonitrile (B). Chromatographic separation was performed by using a Capcell Pak MG-II C18 ($150mm{\times}2.0mm$ i.d., $5{\mu}m$, Shiseido) column and all analytes were eluted within 5 min. Linear least-squares regression with a 1/x weighting factor was used to generate a calibration curve and the assay was linear from 20 to 1500 ng/mL (HAP), 40-3000 ng/mL (AP and RA) and 2-150 ng/mL (MPH). The intra- and inter-day precisions were within 16.4%. The intra- and inter-day accuracies ranged from -15.6% to 10.8%. The limits of detection for all the analytes were less than 4.7 ng/mL. The suitability of the method was examined by analyzing urine samples from drug abusers.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1139-1143
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• 2002

Analysis of lysophosphatidic acids (LPAs) is of clinical importance as they can serve a potential marker for ovarian and other gynecological cancers and obesity. It is critically important to develop a highly sensitive and specific method for the early detection of gynecological cancers to improve the overall outcome of this disease. We have established a novel quantification method of LPAs in human plasma by negative ionization tandem mass spectrometry (MS-MS) using multiple reaction monitoring (MRM) mode without the conventional TLC step. Protein-bound lipids, LPAs in plasma were extracted with methanol : chloroform (2:1) containing LPA C14:0 as an internal standard under acidic condition. Following back extraction with chloroform and water, the centrifuged lower phase was evaporated and reconstituted in methanol. The reconstituted solution was directly injected into electrospray source of MS/MS. For MRM mode, Q1 ions selected were m/z 409, 433, 435, 437 and 457 which corresponds to molecular mass [M-H]- of C16:0, C18:2, C18:1, C18:0 and C20:4 LPA, respectively. Q2 ions selected for MRM were m/z 79, phosphoryl product. Using MS/MS with MRM mode, all the species of LPAs were completely separated from plasma matrix without severe interferences. This method allowed simultaneous detection and quantification of different species of LPAs in a plasma over a linear dynamic range of 0.01-25 ㎛olL-1 . The detection limit of the method was 0.3 pmol/mL, with a correlation coefficient of 0.9983 in most LPAs analyzed. When applied to the plasmas of normal and gynecological cancer patients, this new method differentiated two different groups by way of total LPA level.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.397-401
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• 2009

The complexes of $C_2-\;and\;C_6$-dihydroceramides with transition metal ions have been investigated by using Electrospray ionization-tandem mass spectrometry (ESI-MS/MS). The formation and fragmentation pathways of several doubly charged cluster ions as well as singly charged cluster ions of $C_2-\;and\;C_6$-dihydroceramides with transition metal ions have studied by ESI-MS/MS in the positive mode. Under ESI conditions, dihydroceramides form singly and doubly charged complexes with transition metal ions $(Mn^{2+},\;Fe^{2+},\;Co^{2+},\;Ni^{2+},\;and\;Zn^{2+}\;except\;Cu^{2+})$ with the compositions of $[DHCer+M+2H^2O-H]^+,\;[2DHCer+M+2H2O-H]^+,\;[3DHCer+M+2H2O-H]^+,\;[2DHCer+M]^{2+},\;[3DHCer+M]^{2+},\;[4DHCer+M]^{2+},\;[5DHCer+M]^{2+},\;and\;[6DHCer+M]^{2+}\;(DHCer\;=\;C_2-\;or\;C_6$-dihydroceramide, M = transition metal ion). The different complexation behavior of copper is responsible for relatively lower affinity of dihydroceramides to copper compared to those of other transition metals. It is also found that in the mass spectrum of the dihydroceramide complexes with copper(II), [2DHCer+Cu-H]$^+$ was observed with considerable intensity as well as [2DHCer+Cu+2$H_2O-H]^+$ due to its different geometry from those of other metals.

• Mass Spectrometry Letters
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• 제12권3호
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• pp.66-75
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• 2021

Interleukin-4 (IL-4) and IL-13 are cytokines secreted by immune cells. Cytokines induce the proliferation of macrophages or promote the differentiation of secretory cells. The initiation and progression of allergic inflammatory diseases, such as asthma, are dependent on cytokines acting through related receptor complexes. IL-4 and IL-13 are N-glycoproteins. Glycan structures in glycoproteins play important roles in protein folding, protein stability, enzymatic function, inflammation, and cancer development. Therefore, the glycan structure of IL-4 and IL-13 needs to be elucidated in detail for the development of effective therapies. We report the first attempt to characterize the site-specific N-glycosylation of recombinant IL-4 and IL-13 via liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The tandem mass spectra of intact N-glycopeptides were identified using the Integrated GlycoProteome Analyzer (I-GPA) platform, which can automatically and rapidly analyze multiple N-glycopeptides, including their glycan composition and amino acid sequences. The recombinant IL-4 and IL-13 were identified with amino acid sequence coverages of 84% and 96%, respectively. For IL-4, 52 glycoforms on one N-glycosylation site were identified and quantified. In IL-13, 232 N-glycopeptides from three N-glycosylation sites were characterized, with the site Asn52 being the most extensively glycosylated (~80%). The complex glycans were the most abundant glycan on IL-4 and IL-13 (~96% and 91%, respectively), and the biantennary glycans were the most abundant in both recombinant IL-4 and IL-13 proteins.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.423-428
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• 2022

Very low contents (in the range of 10^-9 g/g) of Ir in mantle-derived rock samples (komatiites) were non-destructively determined by INAA coupled with coincidence gamma-ray spectrometry using 16 Ge detectors. Aliquots of the same samples were analyzed by NiS fire-assay ICP-MS for Ir and other platinum group elements. Because the INAA procedure used in this study is non-destructive and is almost free from spectral interference in gamma-ray spectrometry, the INAA values of Ir contents obtained in this study can be highly reliable. Iridium values obtained by ICP-MS were consistent with the INAA values, implying that the ICP-MS values of Ir obtained in this study are equally reliable. Under the present experimental conditions, detection limits were estimated to be 1 pg/g, which corresponds to 0.1 pg for a sample mass of 0.1 g. These levels can be even lowered by an order of magnitude, if necessary, which cannot be achieved by ICP-MS carried out in this study.

• Mass Spectrometry Letters
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• 제3권3호
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• pp.68-73
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• 2012

Fat malabsorption is an important cause of poor growth in infancy and childhood. Steatorrhea tests have been developed using various methods. Traditional measurements of stool fat, however, require large samples and it often takes as a week to complete the analysis. In this paper, a liquid chromatography-electrospray ionization/mass spectrometry (LC-ESI/MS) method was developed for simultaneous quantitative analysis of triacylglycerols, triolein, diolein and monoolein, in mouse feces. Moreover, the procedure was rapid, simple as well as compatible with LC-ESI/MS. Chloroform-isopropyl alcohol solution was used for fat-soluble sample extraction. After centrifugation and filtration, an analytical solution was prepared. Triolein, diolein and monoolein were separated using non-aqueous reversed-phase column with the mobile phase consisting of A (methanol) and B (acetone-isopropyl alcohol). The precision (% CV) and accuracy (% bias) of the assay were 3.8-14.7% and 85.2-114.9%, respectively. This method has been successfully applied to simultaneous determination of triolein, diolein and monoolein in feces from 30 mice. This method can therefore be applied to measure triacylglycerols in mouse feces accurately and precisely by LC-ESI/MS, thereby helping to predictive biomarker in fat malabsorption and diagnostic research.

• Mass Spectrometry Letters
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• 제9권1호
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• pp.30-36
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• 2018

A quantitation method for free amino acids in human serum was developed using a stepwise-dilution method and a bimodal cation exchange (CEX)/hydrophilic interaction liquid chromatography (HILIC)-tandem mass spectrometry system equipped with an electrospray ionization source (ESI/MS/MS). This method, which was validated using quality control samples, was optimized for enhanced selectivity and sensitivity. Dithiothreitol (DTT) was used as a reducing agent to prevent the oxidation of a serum sample ($50{\mu}L$), which was then subjected to stepwise dilution using 3, 30, and 90 volumes of acetonitrile containing 0.1% formic acid. Chromatographic separation was performed on an Imtakt Intrada Amino Acid column ($50mm{\times}3mm$, $3{\mu}m$) in mixed mode packed with CEX and HILIC ligands embedded in the stationary phase. Underivatized free amino acids were eluted and separated within 10 min. As a result of the validation, the precision and accuracy for the inter- and intraday assays were determined as 2.11-11.51% and 92.82-109.40%, respectively. The lowest limit of quantification (LLOQ) was $0.5-4.0{\mu}g/mL$ and the matrix effect was 80.22-115.93%. The proposed method was successfully applied to the quantitative analysis of free amino acids in human serum.

• Mass Spectrometry Letters
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• 제8권2호
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• pp.23-28
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• 2017

Arctigenin is the main active ingredient of Fructus Arctii, which has been reported with a variety of therapeutic activities including anti-cancer, anti-inflammation, anti-virus, and anti-obesity effects. In this study, a simple and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of arctigenin in rat plasma. The assay utilized a simple protein precipitation with methanol and the mobile phase consisted of 100% methanol and water containing 0.1% formic acid (65:35 v/v). Arctigenin and the internal standard (psoralen) were monitored using a positive electrospray turbo ionspray mode with multiple reaction monitoring transitions of m/z $373.2{\rightarrow}136.9$ and m/z $187.2{\rightarrow}130.9$, respectively, and total chromatographic run time was within 5 min. The lower limit of quantification (LLOQ) of arctigenin was 5 ng/mL in the rat plasma. The intra- and inter-day accuracy of arctigenin at LLOQ and matrix-matched quality control samples ranged 97.4 - 104.8% and 97.2 - 102.0%, respectively. The intra-day precision was within 4.80% and the inter-day precision was within 5.92%. Application of the present method was demonstrated through a pharmacokinetic study after intravenous and oral administration of arctigenin in male Sprague Dawley rats.

• 한국환경보건학회지
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• 제45권3호
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• pp.258-266
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• 2019

Objectives: In this study, blood lead was analyzed using graphite furnace atomic absorption spectrometry (GF-AAs) and inductively coupled plasma mass spectrometry (ICP-MS). We tried to examine the difference and consistency of the analytical values and the applicability of the analytical method. Methods: We selected 57 people who agreed to participate in this study. After confirming the linearity of the calibration standard curves in GF-AAs and ICP-MS, the concentrations of lead in quality control material and samples were measured, and the degree of agreement was compared. Results: The detection limit of the ICP-MS was lower than that of GF-AAs. The coefficient of variation of reference materials was shown to be stable in the ICP-MS and GF-AAs. When the correspondence between the two equipments was verified by bias of the analysis values, a concordance was shown, and approximately 98% of the ideal reference lines were present within ${\pm}40%$ of the deflection. Conclusion: GF-AAs showed high sensitivity to single heavy metal analysis, but it took much time and showed higher detection limit than ICP-MS. Therefore, it would be considered necessary to switch to ICP-MS analysis method, considering that the level of lead exposure is gradually decreasing.

• 분석과학
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• 제30권4호
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• pp.194-204
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• 2017

Direct injection (DI) and solid phase extraction (SPE) methods for the simultaneous determination of pendimethalin (PDM) and dinoseb (DNS) in environmental water have been optimized using the ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. The limits of quantification (LOQs) of PDM and DNS were $0.01{\mu}g/L$ using the DI method and $0.0001-0.0002{\mu}g/L$ using the SPE method. The precision by SPE UPLC-MS/MS was less than 11 % for intra-day and inter-day analyses. When the proposed SPE method was used to analyze two analytes in environmental water, PDM was detected in a concentration range of $0.0002-0.011{\mu}g/L$ in 31 samples of the 114 surface water samples, and DNS was detected in a concentration range of $0.0005-0.045{\mu}g/L$ in 17 samples of the 114 surface water samples analyzed. When the DI method was used to analyze target compounds in the same samples, the detected concentrations of the two analytes were within 21% in samples with concentrations above $0.01{\mu}g/L$. The DI UPLC-MS/MS method can thus be used for the routine monitoring of PDM and DNS in environmental water, and the SPE LC-MS/MS method can be used for the determination of the ultra-trace PDM and DNS residues in environmental water.