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Isotope ratio monitoring of small molecules and macromolecules by liquid chromatography coupled to isotope ratio mass spectrometry
Author(s) -
Godin JeanPhilippe,
Hau Jörg,
Fay LaurentBernard,
Hopfgartner Gérard
Publication year - 2005
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2117
Subject(s) - chemistry , mass spectrometry , isotope , isotope ratio mass spectrometry , chromatography , analytical chemistry (journal) , physics , quantum mechanics
In the field of isotope ratio mass spectrometry, the introduction of an interface allowing the connection of liquid chromatography (LC) and isotope ratio mass spectrometry (IRMS) has opened a range of new perspectives. The LC interface is based on a chemical oxidation, producing CO 2 from organic molecules. While first results were obtained from the analysis of low molecular weight compounds, the application of compound‐specific isotope analysis by irm‐LC/MS to other molecules, in particular biomolecules, is presented here. The influence of the LC flow rate on the CO 2 signal and on the observed δ 13 C values is demonstrated. The limits of quantification for angiotensin III and for leucine were 100 and 38 pmol, respectively, with a standard deviation of the δ 13 C values better than 0.4‰. Also, accuracy and precision of δ 13 C values for elemental analyser‐IRMS and flow injection analysis‐IRMS (FIA‐LC/MS) were compared. For compounds with molecular weights ranging from 131 to 66 390 Da, precision was better than 0.3‰, and accuracy varied from 0.1 to 0.7‰. In a second part of the work, a two‐dimensional (2D)‐LC method for the separation of 15 underivatised amino acids is demonstrated; the precision of δ 13 C values for several amino acids by irm‐LC/MS was better than 0.3‰ at natural abundance. For labelled mixtures, the coefficient of variation was between 1% at 0.07 atom % excess (APE) for threonine and alanine, and around 10% at 0.03 APE for valine and phenylalanine. The application of irm‐LC/MS to the determination of the isotopic enrichment of 13 C‐threonine in an extract of rat colon mucosa demonstrated a precision of 0.5‰, or 0.001 atom %. Copyright © 2005 John Wiley & Sons, Ltd.