Measurement of the stable carbon isotope ratio of atmospheric volatile organic compounds using chromatography, combustion, and isotope ratio mass spectrometry coupled with thermal desorption

Abstract

The isotopic analysis of atmospheric volatile organic compounds (VOCs), and in particular of their stable carbon isotope ratio (δ13C), could potentially be used as an effective tool for identifying the sources of VOCs. However, to date, there have been very few such analyses. In this work, we analyze the δ13C values of VOCs using thermal desorption coupled with chromatography, combustion, and isotope ratio mass spectrometry (TD–GC/C/IRMS). The measured peak shapes were of high quality and 36 compounds in a standard gas containing 58 VOCs (C5–C11) were detected. The measured δ13C varied widely, from −49.7‰ to −22.9‰, while the standard deviation of the δ13C values varied from 0.07‰ to 0.85‰ (n = 5). We then measured samples from two passenger cars in hot and cold modes, three gas stations, roadside air, and ambient air. In comparison with existing studies, the analytical precision for the 36 compounds in this study was reasonable. By comparing the δ13C values obtained from the cars and gas stations, we could identify some degree of the sources of VOCs in the roadside and ambient air samples.