Gas Chromatography Pyrolysis Isotope Ratio Mass Spectrometry Research Articles

Gas chromatography–pyrolysis–isotope ratio mass spectrometry: a new method for investigating intramolecular isotopic variation in low molecular weight organic acids

A new GC–Pyrolysis–IRMS method was developed for the δ13C determination of carboxyl carbon in low-molecular weight organic acids. By utilizing a palladium-wire reactor at 600 °C with a helium/hydrogen reactant gas, the carboxyl carbon of low-molecular weight organic acids is pyrolytically cleaved and introduced into an IRMS for stable carbon-isotope analysis. The precision of the GC–Py–IRMS method is similar to that of more conventional, combustion-based continuous-flow IRMS techniques and interpretation of isotope-dilution experiments with acetic and octanoic acid shows that the technique is sufficiently accurate for the determination of δ13C values at natural abundance levels. As a demonstration of this new capability, the carboxyl carbon of low-molecular weight (LMW, C2–C6) organic acids generated via hydrous pyrolysis of an oil-prone source rock (the Ghareb Shale) shows δ13C values consistent with the hypothesis that organic acids readily undergo exchange of their carboxyl carbon with aqueous inorganic carbon.

2H/1H ratio analysis of flavor compounds by on‐line gas chromatography–pyrolysis–isotope ratio mass spectrometry (HRGC–P–IRMS): citral

AbstractBased on 2H/1H measurements of commercial synthetic and natural citral (neral and geranial), on‐line gas chromatography–pyrolysis–isotope ratio mass spectrometry (HRGC–P–IRMS) was used to determine the δ2HSMOW values of citral in essential oils from Cymbopogon flexuosus and C. citratus, Litsea cubeba, Lippia citriodora, Melissa officinalis and the Citrus species C. aurantium, C. limon, C. sinensis, C. paradisi and C. aurantifolia. The technique allowed reliable differentiation of natural (δ2HSMOW from −236 to −314‰) from synthetic products (δ2HSMOW from +38 to −197‰), even when some samples can also have very negative δ2H values, e.g. −197‰, but permitted no distinction within the origins from the various plant species. Copyright © 2001 John Wiley & Sons, Ltd.