Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2009
Publication Date: 4/2/2009
Citation: Hoh, E., Lehotay, S.J., Mastovska, K., Ngo, H., Vetter, W., Pangallo, K.C., Reddy, C.M. 2009 Capabilities of Direct Sample Introduction - Comprehensive Two-Dimensional Gas Chromatgraphy-Time-of-Flight Mass Spectrometry to Analyze Organic Chemicals of Interest in Fish Oils. Environmental Science and Technology. 43:3240-3247. Interpretive Summary: Persistent organic pollutants (POPs) have been a global concern since the publication of Silent Spring in 1962. They travel over long distances, contaminate remote areas, and accumulate in organisms. Humans are mainly exposed to POPs through food intake. Traditional POPs include polychlorinated biphenyls (PCBs), dioxins, and organochlorine pesticides. Brominated diphenyl ethers (PBDEs) used as flame retardants are emerging POPs. Because of their toxicities, assessment of multiple groups of POPs in food and environmental samples is critical. However, most widely used analytical methods for POPs only analyze a few POPs using laborious sample preparation. To cover a wide range of chemicals, we developed a novel analytical approach conducting both targeted and untargeted analysis simultaneously using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC/TOF-MS) and direct sample introduction (DSI). This analytical approach was evaluated qualitatively and quantitatively for fish oil samples, and we successfully analyzed multiple POPs simultaneously as well as identified untargeted compounds in fish oil with a very simple sample preparation method. This helps improve food safety, risk assessment, and studies of the environmental impact of these type of chemicals.
Technical Abstract: Most analytical methods for persistent organic pollutants (POPs) focus on targeted analytes. Therefore, analysis of multiple classes of POPs typically entails several sample preparations, fractionations, and injections, whereas other chemicals of possible interest are neglected. To analyze a wider scope of organic contaminants in fish oil, we developed an untargeted screening approach using comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (GC×GC/TOF-MS) and direct sample introduction (DSI). The novel approach incorporated a simple sample preparation procedure merely using gel permeation chromatography (GPC) for clean-up of dietary cod liver oil, which provided a wide analytical range of targeted and untargeted chemicals in the same method. Not only could the method quantify and identify several classes of POPs in the samples, but it could also make presumptive identifications of numerous halogenated natural products (HNPs) by comparisons of the mass spectra from analyses with those from mass spectral libraries and/or reports in the literature. Subsequent confirmations were made when possible by re-analysis and comparison of chromatographic retention times and mass spectra with contemporaneously analyzed reference standards. In this paper, ion fragmentation patterns of unusually detected compounds and their sources are discussed. For the first time, several groups of HNPs were identified in cod liver oil at the same time.