Journal of Chromatography A, 1364 (2014) 223–233 Contents lists available at ScienceDirect Journal of Chromatography A j o ur na l ho me page: www.elsevier.com/locate/chroma Two-dimensional gas chromatography/mass spectrometry, physical property modeling and automated production of component maps to assess the weathering of pollutants Patrick M. Antle a , Christian D. Zeigler a , Dimitri G. Livitz b , Albert Robbat a,∗ a Tufts University Department of Chemistry, United States b University of Massachusetts, Amherst, United States a r t i c l e i n f o Article history: Received 3 June 2014 Received in revised form 7 August 2014 Accepted 10 August 2014 Available online 16 August 2014 Keywords: GC × GC/MS Environmental forensics Weathering Component maps Retention index PAH a b s t r a c t Local conditions influence how pollutants will weather in subsurface environments and sediment, and many of the processes that comprise environmental weathering are dependent upon these substances’ physical and chemical properties. For example, the effects of dissolution, evaporation, and organic phase partitioning can be related to the aqueous solubility (S W ), vapor pressure (V P ), and octanol–water par- tition coefficient (K OW ), respectively. This study outlines a novel approach for estimating these physical properties from comprehensive two-dimensional gas chromatography–mass spectrometry (GC × GC/MS) retention index-based polyparameter linear free energy relationships (LFERs). Key to robust correlation between GC measurements and physical properties is the accurate and precise generation of retention indices. Our model, which employs isovolatility curves to calculate retention indices, provides improved retention measurement accuracy for families of homologous compounds and leads to better estimates of their physical properties. Results indicate that the physical property estimates produced from this approach have the same error on a logarithmic-linear scale as previous researchers’ log–log estimates, yielding a markedly improved model. The model was embedded into a new software program, allowing for automated determination of these properties from a single GC × GC analysis with minimal model training and parameter input. This process produces component maps that can be used to discern the mechanism and progression of how a particular site weathers due to dissolution, organic phase parti- tioning, and evaporation into the surrounding environment. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Fossil fuel pollution is the result of a number of factors, including naturally occurring and unintended seepages; collection, trans- port and storage activities; and incomplete combustion. When fossil fuels and their by-products are released into the environ- ment, they are subject to a number of weathering factors. These weathering factors include physical (evaporation, adsorption, dis- solution, and emulsification), biological (microbial degradation), and chemical (photo- and oxidative degradation) processes, all of which can significantly change the chemical composition of the substance over time. Understanding how local environments impact weathering is critical to determining whether the local ecosystem is capable of remediation, i.e., the natural attenuation ∗ Corresponding author at: 62 Talbot Avenue, Medford, MA 02155, United States. Tel.: +1 6176273474. E-mail address: Albert.Robbat@Tufts.edu (A. Robbat). of pollution effects. Because site-specific weathering processes can dramatically change the chemical composition of fossil fuel mix- tures, even at the isomer level [1], it is important to assess these changes as a function of each component’s physical and chemi- cal properties [2]. Once known, one can use this information to determine if natural attenuation is sufficient to reduce pollutant impact on the environment or if active remediation is required. To make this determination, the compositional effects of dissolution, organic phase partitioning, and evaporation must be known; each of which one can examine by studying the aqueous solubility (S W ), octanol–water partition coefficient (K OW ), and vapor pressure (V P ) of sample components, respectively [3,4]. The measurement of aqueous solubility and octanol–water partition coefficient of hydrophobic fossil fuel components such as benzene, polycyclic aromatic hydrocarbons (PAH) and sulfur heterocycles (PASH) and their substituted homologues is time- consuming, challenging, and susceptible to error [5]. For these reasons, gas chromatographic (GC) retention indices (RIs) are often used to estimate these properties [6,7]. GC provides the means to http://dx.doi.org/10.1016/j.chroma.2014.08.033 0021-9673/© 2014 Elsevier B.V. All rights reserved.