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Position-specific carbon isotope analysis of trichloroacetic acid by gas chromatography/isotope ratio mass spectrometry

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Publication date 2011
Author Breider Florian, Hunkeler Daniel,
Project Demonstrating a natural origin of chloroform in groundwater using stable isotope analysis
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Original article (peer-reviewed)

Journal Rapid Communications in Mass Spectrometry
Volume (Issue) 25
Page(s) 1 - 7
Title of proceedings Rapid Communications in Mass Spectrometry
DOI 10.1002/rcm.5276

Abstract

Trichloroacetic acid (TCAA) is an important environmental contaminant present in soils, water and plants. A method for determining the carbon isotope signature of the trichloromethyl position in TCAA using gas chromatography/ combustion/isotope ratio mass spectrometry (GC/C/IRMS) was developed and tested with TCAA from different origins. Position-specific isotope analysis (PSIA) can provide direct information on the kinetic isotope effect for isotope substitution at a specific position in the molecule and/or help to distinguish different sources of a compound. The method is based on the degradation of TCAA into chloroform (CF) and CO2 by thermal decarboxylation. Since thermal decarboxylation is associated with strong carbon isotope fractionation (« = 34.6  0.2%) the reaction conditions were optimized to ensure full conversion. The combined isotope ratio of CF and CO2 at the end of the reaction corresponded well to the isotope ratio of TCAA, confirming the reliability of the method. A method quantification limit (MQL) for TCAA of 18.6 mg/L was determined. Samples of TCAA produced by enzymatic and non-enzymatic chlorination of natural organic matter (NOM) and some industrially produced TCAA were used as exemplary sources. Significant different PSIA isotope ratios were observed between industrial TCAA and TCAA samples produced by chlorination of NOM.
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