Highlighting the Effects of Co-eluting Interferences on Compound-Specific Stable Isotope Analysis of Polycyclic Aromatic Hydrocarbons by Using Comprehensive Two-Dimensional Gas Chromatography

Authors

  • Dr. Caroline Gauchotte-Lindsay,

    Corresponding author
    1. Department of Civil and Environmental Engineering, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow (United Kingdom)
    2. Current address: Infrastructure and Environment Research Division, School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow (United Kingdom)
    • Department of Civil and Environmental Engineering, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow (United Kingdom)

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  • Dr. Laura A. McGregor,

    1. Department of Civil and Environmental Engineering, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow (United Kingdom)
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  • Dr. Antoine Assal,

    1. Department of Civil and Environmental Engineering, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow (United Kingdom)
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  • Dr. Russell Thomas,

    1. Parsons Brinckerhoff, Queen Victoria House, Redland Hill, Bristol (United Kingdom)
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  • Prof. Robert M. Kalin

    1. Department of Civil and Environmental Engineering, University of Strathclyde, John Anderson Building, 107 Rottenrow, Glasgow (United Kingdom)
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Abstract

Accuracy is the most important issue when performing compound-specific stable isotope analysis of polycyclic aromatic hydrocarbons (PAHs) extracted from complex samples. It depends on two main factors: the possible isotopic fractionation of the compounds during extraction and the potential co-elution with interfering compounds with different isotopic signatures. Herein, a simplified pressurised liquid extraction method for compound-specific stable isotope analysis of PAHs in non-aqueous-phase liquids of coal tar is presented. Samples extracted using the new method and by fractionation on a silica gel column were analysed by comprehensive two-dimensional gas chromatography. It was possible to evaluate the effect of co-elution on the carbon and hydrogen stable isotope signatures of the 16 US EPA priority PAHs in coal tars with various proportions of aromatic and aliphatic content. Even in samples that presented a good baseline resolution, the PAHs of interest co-eluted with other aromatic compounds with a notable effect on their stable isotope values; this demonstrated the necessity to check the quality of all extraction and clean-up methods (either the simplified pressurised liquid extraction or more traditional labour-intensive methods) for more complex samples prior to data interpretation. Additionally, comprehensive two-dimensional gas chromatography enabled visualisation of the suspected co-elution for the first time.

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