Determination of nitrogen-15 isotope fractionation in tropine: evaluation of extraction protocols for isotope ratio measurement by isotope ratio mass spectrometry - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Rapid Communications in Mass Spectrometry Année : 2009

Determination of nitrogen-15 isotope fractionation in tropine: evaluation of extraction protocols for isotope ratio measurement by isotope ratio mass spectrometry

Résumé

N-Demethylation of tropine is an important step in the degradation of this compound and related metabolites. With the purpose of understanding the reaction mechanism(s) involved, it is desirable to measure the N-15 kinetic isotope effects (KIEs), which can be accessed through the N-15 isotope shift (Delta delta N-15) during the reaction. To measure the isotope fractionation in N-15 during tropine degradation necessitates the extraction of the residual substrate from dilute aqueous solution without introducing artefactual isotope fractionation. Three protocols have been compared for the extraction and measurement of the N-15/N-14 ratio of tropine from aqueous medium, involving liquid-liquid phase partitioning or silica-C18 solid-phase extraction. Quantification was by gas chromatography (CC) on the recovered organic phase and delta N-15 values were obtained by isotope ratio measurement mass spectrometry (irm-MS). Although all the protocols used can provide satisfactory data and both irm-EA-MS and irm-GC-MS call be used to obtain the delta N-15 values, the most convenient method is liquid-liquid extraction from a reduced aqueous volume combined with irm-GC-MS. The protocols are applied to the measurement of N-15 isotope shifts during growth of a Pseudomonas strain that uses tropane alkaloids as sole source of carbon and nitrogen. The accuracy of the determination of the N-15/N-14 ratio is sufficient to be used for the determination of N-15-KIEs. Copyright (C) 2009 John Wiley & Sons, Ltd.

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Chimie

Dates et versions

hal-02143506 , version 1 (29-05-2019)

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Citer

Roland Molinie, Renata A. Kwiecien, Virginie Silvestre, Richard J. Robins. Determination of nitrogen-15 isotope fractionation in tropine: evaluation of extraction protocols for isotope ratio measurement by isotope ratio mass spectrometry. Rapid Communications in Mass Spectrometry, 2009, 23 (24), pp.4031-4037. ⟨10.1002/rcm.4344⟩. ⟨hal-02143506⟩
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