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High‐temperature pyrolysis/gas chromatography/isotope ratio mass spectrometry: simultaneous measurement of the stable isotopes of oxygen and carbon in cellulose
Author(s) -
Woodley Ewan J.,
Loader Neil J.,
McCarroll Danny,
Young Giles H. F.,
Robertson Iain,
Heaton Timothy H. E.,
Gagen Mary H.,
Warham Joseph O.
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.5302
Subject(s) - chemistry , pyrolysis , isotope ratio mass spectrometry , mass spectrometry , cellulose , gas chromatography , chromatography , isotopic signature , oxygen , isotopes of oxygen , pyrolysis–gas chromatography–mass spectrometry , isotope , stable isotope ratio , analytical chemistry (journal) , isotopes of carbon , carbon fibers , radiochemistry , environmental chemistry , organic chemistry , nuclear chemistry , total organic carbon , composite material , physics , materials science , quantum mechanics , composite number
Stable isotope analysis of cellulose is an increasingly important aspect of ecological and palaeoenvironmental research. Since these techniques are very costly, any methodological development which can provide simultaneous measurement of stable carbon and oxygen isotope ratios in cellulose deserves further exploration. A large number (3074) of tree‐ring α‐cellulose samples are used to compare the stable carbon isotope ratios (δ 13 C) produced by high‐temperature (1400°C) pyrolysis/gas chromatography (GC)/isotope ratio mass spectrometry (IRMS) with those produced by combustion GC/IRMS. Although the two data sets are very strongly correlated, the pyrolysis results display reduced variance and are strongly biased towards the mean. The low carbon isotope ratios of tree‐ring cellulose during the last century, reflecting anthropogenic disturbance of atmospheric carbon dioxide, are thus overestimated. The likely explanation is that a proportion of the oxygen atoms are bonding with residual carbon in the reaction chamber to form carbon monoxide. The 'pyrolysis adjustment', proposed here, is based on combusting a stratified sub‐sample of the pyrolysis results, across the full range of carbon isotope ratios, and using the paired results to define a regression equation that can be used to adjust all the pyrolysis measurements. In this study, subsamples of 30 combustion measurements produced adjusted chronologies statistically indistinguishable from those produced by combusting every sample. This methodology allows simultaneous measurement of the stable isotopes of carbon and oxygen using high‐temperature pyrolysis, reducing the amount of sample required and the analytical costs of measuring them separately. Copyright © 2011 John Wiley & Sons, Ltd.