Use of a temperature‐programmable injector coupled to gas chromatography–combustion–isotope ratio mass spectrometry for compound‐specific carbon isotopic analysis of polycyclic aromatic hydrocarbons

Abstract

Compound-specific isotopic analysis (CSIA) can provide information about the origin of analysed compounds; for instance, polycyclic aromatic hydrocarbons (PAHs) in aerosols. This could be a valuable tool in source apportionment of particulate matter (PM) air pollution. Because gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis requires an amount of at least 10 ng of an individual PAH, a high concentration of PAHs in the injected extract is needed. When the concentration is low a large volume injector creates the possibility of introducing a satisfactory amount of individual PAHs. In this study a temperature-programmable injector was coupled to GC-C-IRMS and injection parameters (solvent level, transfer column flow, transfers time) were optimised using six solid aromatic compounds (anthracene, fluoranthene, pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene) dissolved in n-pentane and EPA 610 reference mixture. CSIA results for solid PAHs were compared with results obtained for the single components analysed by elemental analysis-isotope ratio mass spectrometry. The injection method was validated for two sample injection volumes, 50 and 100 microL. This method was also compared with commonly used splitless injection. To be included in the study, measurements had to have an uncertainty lower than 0.5 per thousand for delta(VPDB)13C and a minimum peak height of 200 mV. The lower concentration limits at which these criteria were fulfilled for PAHs were 30 mg/L for 1 microL in splitless injection and 0.3 and 0.2 mg/L for 50 and 100 microL, respectively, in large volume injection.

Large-volume injection combined with gas chromatography/isotope ratio mass spectrometry for the analysis of polycyclic aromatic hydrocarbons

“…Parameters previously optimized for the LVI (100 μL) of PAHs in n ‐pentane were initially adopted for injections in n ‐hexane. The organic solvent was changed to n ‐hexane because of its higher boiling point, which facilitates the complete removal of dichloromethane (DCM) during the sample concentration step.…”

“…It should be mentioned that all the above publications dealt with the application of LVI for mass spectrometry detection while applications of LVI for isotopic ratio mass spectrometry approaches are scarce. The aim of this study was to optimize the large‐volume injection of 16 EPA PAHs for stable carbon isotope ratio analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GCCIRMS).…”

Analysis of polycyclic aromatic hydrocarbons extracted from air particulate matter using a temperature programmable injector coupled to GC–C–IRMS†

“…The LVI-GC-C-IRMS method was validated in our laboratory using pure, solid aromatic compounds and EPA 610 reference mixture [20].…”

Optimization of a large‐volume injection method for compound‐specific isotope analysis of polycyclic aromatic compounds at trace concentrations

“…Recent studies have validated LVI for the isotopic analysis of PAHs based on the injection of 100 μL of n-pentane and n-hexane, respectively. [27][28][29] These authors observed substantial losses of analytes with a two-to three-ring structure occurring at an injection temperature of 45°C. Buczynska et al [29] optimized the method by using n-hexane with 5% toluene as co-solvent to reduce discrimination against lowmolecular-weight PAHs.…”

“…Although LVI techniques are commonly used in the quantitative analysis of semi‐volatile compounds such as polychlorinated biphenyls, pesticides and polycyclic aromatic hydrocarbons, applications of a large‐volume sample introduction technique for compound‐specific isotope analysis with GC/IRMS are still scarce. Recent studies have validated LVI for the isotopic analysis of PAHs based on the injection of 100 μL of n ‐pentane and n ‐hexane, respectively . These authors observed substantial losses of analytes with a two‐ to three‐ring structure occurring at an injection temperature of 45 °C.…”