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

Abstract

R. M. (2014) Highlighting the effects of co-eluting interferences on compound specific stable isotope analysis of polycyclic aromatic hydrocarbons using comprehensive two-dimensional gas chromatography. ChemPlusChem, 79 (6). pp. 804-812. ISSN 2192-6506 Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A copy can be downloaded for personal non-commercial research or study, without prior permission or charge Content must not be changed in any way or reproduced in any format or medium without the formal permission of the copyright holder(s) When referring to this work, full bibliographic details must be given http://eprints.gla.ac.uk/93257/ Accuracy is the most important issue when carrying out compound specific stable isotope analysis of polycyclic aromatic hydrocarbons 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. We present here a simplified pressurised liquid extraction method for compound specific stable isotope analysis of polycyclic aromatic hydrocarbons (PAHs) in non-aqueous phase liquids of coal tar. Samples extracted using the new method and using fractionation on silica gel column were analysed using comprehensive twodimensional gas chromatography. We were able to evaluate the effect of coelution on carbon and hydrogen stable isotope signatures of the 16 US EPA priority PAHs in the 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; it demonstrated the necessity to check the quality of all extraction and clean-up methods (either the simplified pressurized liquid extraction or more traditional labour-intensive methods) for the more complex samples prior to data interpretation. Additionally, comprehensive twodimensional gas chromatography enabled visualisation of the suspected coelutions for the first time. IntroductionPolycyclic aromatic hydrocarbons (PAHs) are a ubiquitous global contaminant, produced by a number of sources, including vehicle emissions and fuel combustion1. Many PAHs are known to have toxic, mutagenic and carcinogenic properties2, making their source, fate and remediation within the environment a highly studied topic. However, due to the great number (and similarity) of potential PAH sources it is often difficult to provide irrefutable source attribution. This is evident in the analysis of coal tars, a by-product produced by manufactured gas plants (MGPs), often found in high volumes at contaminated former MGP sites across Europe and North America3. Isotope studies have gained much popularity within environmental forensic investigations, due to their ability to differentiate between chemically identical contaminants4. Compound-specific isotope analysis (CSIA) has the additional ability to measure the isotop...

Rapid sequential separation of sedimentary lipid biomarkers via selective accelerated solvent extraction

“…unresolved complex mixtures; Fig. 2), which complicate lipid characterization and quantification (Eiserbeck et al, 2012;Gauchotte-Lindsay et al, 2014). Therefore, environmental TLEs and derived lipid fractions were characterized using total ion chromatograms (TICs) with complementary selected ion monitoring (SIM) of m/z 85 (saturated hydrocarbons), m/z 91+97 (unsaturated/aromatic hydrocarbons) and m/z 202+252 (PAHs; Wang and Fingas, 2003;Peters et al, 2005).…”

“…Recent studies show promising results for the separation of FARO according to aromaticity (i.e. unsaturated/aromatic hydrocarbons; Kim et al, 2003Wiesenberg et al, 2004Gauchotte-Lindsay et al, 2014). In addition, separation using ASE columns shows promise for further division of compounds in FPOL according to unsaturation (e.g.…”

“…Many paleoenvironmental and energy related organic geochemical studies require separation of complex extracts into more discrete compound fractions prior to molecular and isotopic characterization. Although recent studies using ASE have incorporated multiple adsorbents (Muijs and Jonker, 2009;Pena et al, 2010;Zhang et al, 2012;Do et al, 2013) or multiple solvent sequences (Björklund et al, 2006;Lundstedt et al, 2006;Zuloaga et al, 2012), they focused on exclusion of undesirable compounds rather than on separation or isolation of desirable compounds (Gauchotte-Lindsay et al, 2014). These studies suggest that ASE selective separation has potential for isolating entire compound fractions from complex mixtures extracted from sediments and sedimentary rocks via a combination of both multiple stationary (adsorbent) and mobile (solvent) phases.…”

Evaluation of coal‐related model compounds using tandem mass spectrometry

“…The identification of compounds in coal using GC/MS can be disturbed by co‐eluted species, which hamper the monitoring of coal conversions like hydrodeoxygenation, hydrodenitrogenation and hydrodesulfurization. The structure‐elucidating power of GC/MS is expected to improve via the MS/MS method.…”

“…31,32 SRM/MRM methods run by GC/Q-TOF MS were shown to eliminate most non-target detection and improve specificity and sensitivity. 33,34 The identification of compounds in coal using GC/MS can be disturbed by co-eluted species, 35,36 which hamper the monitoring of coal conversions like hydrodeoxygenation, hydrodenitrogenation and hydrodesulfurization. The structure-elucidating power of GC/MS is expected to improve via the MS/MS method.…”