New 2DGC-IRMS Method Developed for Accurate Analysis of High Molecular Weight PAHs in Sediments

Scientists at the Chinese Academy of Sciences in Guangzhou have developed a new method for accurately analyzing high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) in estuarine/marine sediments. The method involves using a two-dimensional gas chromatography-isotope ratio mass spectrometry (2DGC-IRMS) system, which was constructed by hyphenating an extra gas chromatography system (GC) to a conventional GC-IRMS using a commercially available multi-column switching-cryogenic trapping system (MCS-CTS).

Sediment and rock layers at Karijini National Park in Dales Gorge including natural asbestos | Image Credit: © MXW Photo - stock.adobe.com

2DGC-IRMS is a powerful analytical tool that combines two-dimensional gas chromatography with isotope ratio mass spectrometry. It allows for the separation of complex mixtures of compounds, such as pollutants in environmental samples, and the precise determination of their isotopic composition. The 2DGC-IRMS system can be used to identify the sources of pollutants and trace their fate in the environment. It has potential applications in fields such as environmental science, forensic science, and food science.

This new method improves upon previous 2DGC-IRMS strategies by purifying target analytes online and enriching them via duplicate injection and cryogenic trapping in CTS, resulting in lower limits of detection (LOD) of compound-specific isotope analysis (CSIA). The method also uses a broader-bore and longer fused-silica capillary to improve sample transfer efficiency to the IRMS. The successful application of this newly developed 2DGC-IRMS scheme provides a practical solution for the reliable CSIA of trace-level pollutants in complex environmental samples that cannot be measured using the conventional GC-IRMS system.

PAHs in estuarine sediments have gained attention in health science and ecology due to their potential adverse effects on human beings and coastal ecosystems. They are primarily caused by human activities such as industrial and agricultural production processes, vehicle exhaust, coal and biomass combustion, and emissions of petroleum-related products. The new method for accurately analyzing HMW-PAHs will be useful in determining the origin and fate of organic pollutants in sediments, and in identifying sources of PAHs in air, sediments, and soils.

The study, published in the Journal of Chromatography A, showed accurate δ¹³C values and high precisions with the LOD of HMW-PAHs reduced to at least 1.0 mg/L (1). The successful application of this newly developed 2DGC-IRMS scheme provides a practical solution for the reliable CSIA of trace-level pollutants in complex environmental samples that cannot be measured using the conventional GC-IRMS system. This method will be valuable in future studies of environmental pollution and will aid in the development of effective mitigation strategies.

Reference

(1) Tian, B.; Gao, S.; Zhu, Z.; Zeng, X.; Liang, Y.; Yu, Z.; Peng, P. Two-dimensional gas chromatography coupled to isotope ratio mass spectrometry for determining high molecular weight polycyclic aromatic hydrocarbons in sediments. J. Chromatogr. A 2023, 1693, 463879. DOI: https://doi.org/10.1016/j.chroma.2023.463879