LC-UV-Solid-Phase Extraction-NMR-MS Combined with a Cryogenic Flow Probe and Its Application to the Identification of Compounds Present in Greek Oregano

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• 作者：Vassiliki Exarchou ; Markus Godejohann ; Teris A. van Beek ; Ioannis P. Gerothanassis ; and Jacques Vervoort
• 刊名：Analytical Chemistry
• 出版年：2003
• 出版时间：November 15, 2003
• 年：2003
• 卷：75
• 期：22
• 页码：6288 - 6294
• 全文大小：140K
• 年卷期：v.75,no.22(November 15, 2003)
• ISSN：1520-6882

文摘

Structure elucidation of natural products usually relieson a combination of NMR spectroscopy with mass spectrometry whereby NMR trails MS in terms of the minimumsample amount required. In the present study, the usefulness of on-line solid-phase extraction (SPE) in LC-NMRfor peak storage after the LC separation prior to NMRanalysis is demonstrated. The SPE unit allows the use ofnormal protonated solvents for the LC separation and fullydeuterated solvents for flushing the trapped compoundsto the NMR probe. Thus, solvent suppression is no longernecessary. Multiple trapping of the same analyte fromrepeated LC injections was utilized to solve the problemof low concentration and to obtain 2D heteronuclear NMRspectra. In addition, a combination of the SPE unit witha recently developed cryoflow NMR probe and an MS wasevaluated. This on-line LC-UV-SPE-NMR-MS system wasused for the automated analysis of a Greek oreganoextract. Combining the data provided by the UV, MS, andNMR spectra, the flavonoids taxifolin, aromadendrin,eriodictyol, naringenin, and apigenin, the phenolic acidrosmarinic acid, and the monoterpene carvacrol wereidentified. This automated technique is very useful fornatural product analysis, and the large sensitivity improvement leads to significantly reduced NMR acquisitiontimes.