- Enhancement of the LC/MS analysis of fatty acids through derivatization and stable isotope coding
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This paper focuses on the development of an enhanced LC/ESI-MS method for the identification and quantification of fatty acids through derivatization. Fatty acids were derivatized with 2-bromo-1-methylpyridinium iodide and 3-carbinol-1-methylpyridinium iodide, forming 3-acyloxymethyl-1-methylpyridinium iodide (AMMP). This process attaches a quaternary amine to analytes and enabled ESI-MS in the positive mode of ionization with common LC mobile phases. Moreover, detection sensitivity was generally 2500-fold higher than in the negative mode of ionization used with underivatized fatty acids. The limits of detection were roughly 1.0-4.0 nM (or 10 pg/injection) for standard fatty acids from C10 to C24 and spanned ~2 orders of magnitude in linearity. AMMP derivatives had unique tandem mass spectra characterized by common ions at m/z 107.0, 124.0, and 178.0. Individual fatty acids also had unique fingerprint regions that allowed identification of their carbon skeleton number, number of double bonds, and double bond position. The derivatization method also allowed coding of analytes as a means of recognizing derivatives and enhancing quantification. 2H-Coding was achieved through derivatization with deuterated 3-carbinol-1-methyl-d3-pyridinium iodide. The 2H-coded derivatization reagent, 3-acyloxymethyl-1-methyl-d 3-pyridinium iodide, was used in two ways. One was to differentially label equal fractions of a sample such that after being recombined and analyzed by ESI-MS all fatty acids appeared as doublet clusters of ions separated by roughly 3 amu. This greatly facilitated identification of fatty acids in complex mixtures. Another use of stable isotope coding was in comparative quantification. Control and experimental samples were differentially labeled with nondeuterated and deuterated isotopomers of CPM, respectively. After mixing the two samples, they were analyzed by ESI-MS. The abundance of a fatty acid in an experimental sample relative to the control was established by the isotope ratio of the isotopomeric fatty acids. Absolute quantification was achieved by adding differentially labeled fatty acid standards to experimental samples containing unknown quantities of fatty acids. Utility of the method was examined in the analysis of human serum samples.
- Yang, Wen-Chu,Adamec, Jiri,Regnier, Fred E.
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- Development of a sensitive and quantitative method for the identification of two major furan fatty acids in human plasma
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This article focuses on the establishment of an accurate and sensitive quantitation method for the analysis of furan fatty acids. In particular, the sensitivity of GC/MS and UPLC/ESI/MS/MS was compared for the identification and quantification of furan fatty acids. Different methylation methods were tested with respect to GC/MS analysis. Special attention needs to be paid to the methylation of furan fatty acids, as acidic catalysts might lead to the degradation of the furan ring. GC/MS analysis in full-scan mode demonstrated that the limit of quantitation was 10 μM. UPLC/ESI/MS/MS in multiple reaction monitoring mode displayed a higher detection sensitivity than GC/MS. Moreover, the identification of furan fatty acids with charge-reversal derivatization was tested in the positive mode with two widely used pyridinium salts. Significant oxidation was unexpectedly observed using N-(4-aminomethylphenyl) pyridinium as a derivatization agent. The formed 3-acyl-oxymethyl-1-methylpyridinium iodide derivatized by 2-bromo-1-methylpyridinium iodide and 3-carbinol-1-methylpyridinium iodide improved the sensitivity more than 2,000-fold compared with nonderivatization in the negative mode by UPLC/ESI/MS/MS. This charge-reversal derivatization enabled the targeted quantitation of furan fatty acids in human plasma. Thus, it is anticipated that this protocol could greatly contribute to the clarification of pathological mechanisms related to furan fatty acids and their metabolites.
- Hu, Changfeng,Li, Siming,Liu, Yongguo,Vetter, Walter,Wang, Yonghua,Xu, Long,Yin, Huiyong
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- BTEX METABOLITES DERIVATIZATION KIT AND COMPOSITION
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A kit or composition for in situ simultaneously derivatization of 14 phenol and carboxylic acid metabolites of benzene, toluene, ethylbenzene, and xylene (BTEX) in a urine sample is disclosed. The derivatization imparts a positive charge to phenol and carboxylic acid for subsequent LC-MS analysis. Limit of detection reached part-per-trillion levels for o-Cresol and part-per-billion levels for the remaining BTEX metabolites. BTEX metabolites can be detected in less than 35 mins according to one embodiment of the invention. Methods, kits and compositions disclosed herein can be used for in situ simultaneous derivatization of phenol and carboxylic acid in aqueous solution in general.
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Paragraph 0056
(2019/11/22)
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- Synthesis of piperidine derivatives by reduction of pyridinium salts
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Piperidine derivatives 1a-e and 2a-f have been prepared by the reduction of 3-and 4-substituted pyridinium salts with NaBH4 in moderate to excellent yields. The reactions regioselectively give 1,2,5,6-tetrahydropyridines, and the yields depend greatly upon the nature of substituents on the phenyl ring and on the nitrogen atom, the nature and the position of the substituents on the pyridyl ring, and the chain length between the aryloxy and the pyridyl groups. Copyright Taylor & Francis Group, LLC.
- Tang, Zilong,Mayrargue, Joelle,Alami, Mouad
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p. 3367 - 3379
(2008/02/13)
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- SYNTHESIS AND REACTIVITY OF 2-(1,3-DITHIAN-2-YL)INDOLES. III. INFLUENCE OF THE INDOLE PROTECTIVE N-PHENYLSULFONYL GROUP
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Formation of the anion of 2-(1,3-dithian-2-yl)indoles was shown to be possible when the indole nitrogen is protected by a p-methoxyphenylsulfonyl group.In contrast to the corresponding N-phenylsulfonylindole dithiane 1, the anion of dithiane 2 reacts efficiently with electrophiles.The influence of the indole protective group on the metallation of 2-bis(ethylthio)-methyl-1-(phenylsulfonyl)indole (14) and the corresponding sulfoxide 24 with n-butyllithium is also reported.
- Rubiralta, Mario,Diez, Anna,Reig, Ignasi,Castells, Josep,Bettiol, Jean-Luc,et al.
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p. 173 - 186
(2007/10/02)
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