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Can gas chromatography combustion isotope ratio mass spectrometry be used to quantify organic compound abundance?
Author(s) -
Thornton Barry,
Zhang Zulin,
Mayes Robert W.,
Högberg Mo.,
Midwood Andrew J.
Publication year - 2011
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.5148
Subject(s) - chemistry , isotope ratio mass spectrometry , gas chromatography , mass spectrometry , chromatography , gas chromatography–mass spectrometry , isotope analysis , flame ionization detector , isotopes of carbon , isotope , analytical chemistry (journal) , combustion , environmental chemistry , organic chemistry , total organic carbon , ecology , physics , quantum mechanics , biology
Quantifying the concentrations of organics such as phospholipid fatty acids (PLFAs) and n ‐alkanes and measuring their corresponding 13 C/ 12 C isotope ratios often involves two separate analyses; (1) quantification by gas chromatography flame ionisation detection (GC‐FID) or gas chromatography/mass spectrometry (GC/MS), and (2) 13 C‐isotope abundance analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC‐C‐IRMS). This requirement for two separate analyses has obvious disadvantages in terms of cost and time. However, there is a history of using the data output of isotope ratio mass spectrometers to quantify various components; including the N and C concentrations of solid materials and CO 2 concentrations in gaseous samples. Here we explore the possibility of quantifying n ‐alkanes extracted from sheeps' faeces and fatty acid methyl esters (FAMEs) derivatised from PLFAs extracted from grassland soil, using GC‐C‐IRMS. The results were compared with those from GC‐FID analysis of the same extracts. For GC‐C‐IRMS the combined area of the masses for all the ions ( m/z 44, 45 and 46) was collected, referred to as 'area all', while for the GC‐FID analysis the peak area data were collected. Following normalisation to a common value for added internal standards, the GC‐C‐IRMS 'area all' values and the GC‐FID peak area data were directly compared. Strong linear relationships were found for both n ‐alkanes and FAMEs. For the n ‐alkanes the relationships were 1:1 while, for the FAMEs, GC‐C‐IRMS overestimated the areas relative to the GC‐FID results. However, with suitable reference material 1:1 relationships were established. The output of a GC‐C‐IRMS system can form the basis for the quantification of certain organics including FAMEs and n ‐alkanes. Copyright © 2011 John Wiley & Sons, Ltd.