Characterization of Aqueous Film Forming Foam (AFFF) Using Multivaraite Analysis

Poster Presentation

Prepared by D. Stevens1, A. Karmann2, L. Mullin1, G. Cleland1
1 - Waters Corporation, 34 Maple Street, Milford, MA, 01757, United States
2 - Írebro University, MTM Research Centre, Írebro , SE-701 82, Sweden


Contact Information: doug_stevens@waters.com; 508-482-4672


ABSTRACT

Aqueous film forming foams (AFFFs) are used in both military and commercial firefighting. Use of these formulations has resulted in the release of contaminants into the environment due to migration from the site of application. The various formulations of AFFFs consist of mixtures of fluorocarbon and hydrocarbon compounds1. Characterizing the unique, as well as common, components of AFFFs currently in use is the starting point to tracking their constituents through various environmental and biological compartments. In this study, seven AFFF mixtures were analyzed using QTof MS in order to obtain full spectral acquisition and to apply multivariate analysis to the data to identify unique components of the mixtures.

Data was acquired using alternating high and low collision energy conditions so that both precursor and product ions were acquired in a single injection. Samples were diluted in methanol and chromatographic separation performed using an existing liquid chromatography method for the analysis of perfluorinated compounds. Method performance with regards to mass accuracy (<5 ppm mass error), retention time conservation and repeatability of analyte response is particularly important in experiments involving non-targeted analysis. These analytical measures were assessed using a solvent standard mixture of perfluorinated compounds. Randomized multiple injections of the seven mixtures were then subjected to a principal component analysis (PCA).

Distinctive groupings from PCA plots were observed for three AFFFs in both modes with a cluster of five of the seven in ESI+ and four of the seven in ESI-. Pooled samples, which contain all ions used in the multivariate analysis, were clustered appropriately towards the middle of the graph. In order to determine formulation specific markers, group-to-group comparisons were carried out with two foams at a time, resulting in the generation of S-Plots. Investigation of the markers strongly associated with specific groups was performed using structural elucidation software tools. This resulted in the identification of multiple sulfate, hydrocarbon and fluorinated compounds. Further interrogation of the markers using trend plots, which indicate presence and abundance across injections, yielded additional identifications that were either unique to specific formulations or in some cases common compounds to multiple AFFFs. For those constituents that had a proposed structure, production structures were assigned and used as a means to support a potential identification.

The relevance of both the analytical technique and software processing approach applied for environmental forensic analysis will be discussed.