Atmospheric Environment 40 (2006) 3381–3388 d 13 C of volatile organic compounds (VOCS) in airborne samples by thermal desorption-gas chromatography-isotope ratio-mass spectrometry (TD-GC-IR-MS) Nicole Turner a , Mark Jones b , Kliti Grice a,Ã , Daniel Dawson a , Marisa Ioppolo-Armanios b , Steven J. Fisher a a Stable isotope and Biogeochemistry Group, Centre for Applied Organic Geochemistry, Curtin University of Technology. Perth, WA 6845, Australia b Alcoa World Alumina, Australia, Technology Delivery Group, PO Box 161, Kwinana WA 6167, Australia Received 8 November 2005; accepted 12 January 2006 Abstract This paper is a preliminary investigation into the use of a thermal desorption-gas chromatography-isotope ratio mass spectrometry (TD-GC-IR-MS) method to determine stable carbon isotopic compositions (d 13 C) of low molecular-weight volatile organic compounds (VOCs) in airborne samples (e.g. industrial and car exhaust emissions) as a means of differentiating their sources in the environment. A TD-GC-IR-MS method for obtaining d 13 C of VOCs (benzene, toluene, chlorobenzene, ethylbenzene, m-xylene and propylbenzene) in air samples has been optimised, and is proven to be both reproducible and linear. The d 13 C of the VOC standards was found to be comparable (within analytical error) to that obtained from direct GC-IR-MS analysis. This novel method of VOC analysis is valuable in environmental and forensic investigations. r 2006 Elsevier Ltd. All rights reserved. Keywords: Thermal desorption; Environmental contaminants; Volatile organic compounds; Stable carbon isotopes; Airborne samples 1. Introduction The atmosphere contains a complex mixture of organic compounds, as either volatiles or aerosol particulates. These organic compounds derive from a variety of natural materials (e.g. wind-blown plant waxes, vegetation and soils) or from anthropogenic emissions (e.g. vehicle exhaust and industrial effluents/soot). Volatile organic compounds (VOCs) are compounds normally present in the vapour phase or gas form at room temperature (vapour pressure greater than 0.1 mm Hg at 25 1C), exclud- ing methane (Kelly et al., 1994). For several years the use of solid adsorbent tubes has proved to be a suitable sampling technique for airborne VOCs, either coupled with a pump (active sampling) or in tubes used in the diffusive mode (i.e. passive sampling) (e.g. Brown et al., 1981; Brown and Wright, 1994). Traditional sorbents (i.e. active ARTICLE IN PRESS www.elsevier.com/locate/atmosenv 1352-2310/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2006.01.030 Ã Corresponding author. Tel.: +618 9266 2474; fax: +618 9266 2300. E-mail addresses: Nicole.Turner@csiro.au (N. Turner), Mark.Jones@alcoa.com.au (M. Jones), K.Grice@curtin.edu.au (K. Grice), D.Dawson@curtin.edu.au (D. Dawson), Marisa.Ioppolo-Armanios@alcoa.com.au (M. Ioppolo-Armanios), sfisher@fish.wa.gov.au (S.J. Fisher).