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Automated analysis of 13 C/ 12 C ratios in CO 2 and dissolved inorganic carbon for ecological and environmental applications
Author(s) -
Torn Margaret S.,
Davis Simon,
Bird Jeffrey A.,
Shaw M. Rebecca,
Conrad Mark E.
Publication year - 2003
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.1246
Subject(s) - chemistry , tracer , analytical chemistry (journal) , isotope analysis , isotopes of carbon , analyte , stable isotope ratio , isotope , mass spectrometry , volume (thermodynamics) , carbon fibers , isotope ratio mass spectrometry , environmental chemistry , total organic carbon , chromatography , ecology , physics , materials science , quantum mechanics , composite number , nuclear physics , composite material , biology
Stable carbon isotope ratios ( 13 C/ 12 C) are a valuable tool for studying a wide range of environmental processes, including carbon cycling and subsurface microbial activity. Recent advances in automated analysis provide the opportunity to increase greatly the ease and consistency of isotopic analysis. This study evaluated an automated headspace sampler linked to a commercially available CO 2 preconcentration system and continuous flow isotope ratio mass spectrometer. Field sampling and analysis methods are illustrated for δ 13 C of soil respired CO 2 , from both tracer and natural abundance experiments, and dissolved inorganic carbon from contaminated groundwater. The automated system demonstrated accuracy, precision, and linearity, with standard errors below 0.1‰ for replicate gas standards run at concentrations varying five‐fold. It measured 40 samples per 10‐hour run, with concentrations ranging from ppb to percentage levels. In the field, gas samples were injected into nitrogen‐filled autosampler vials, thereby allowing use of small sample volumes, control of analyte concentration, and direct analysis by the automated system with no further preparation. A significant linear relationship between standard concentrations and peak area allows for accurate estimates of sample CO 2 concentration from the mass spectrometric data. The ability to analyze multiple small‐volume samples with minimal off‐line preparation should enhance the application of isotopes to well‐replicated field experiments for process‐level studies and spatial and temporal scaling. Copyright © 2003 John Wiley & Sons, Ltd.