Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2008
Publication Date: 8/1/2008
Citation: Hoh, E., Lehotay, S.J., Mastovska, K., Huwe, J.K. 2008. Evaluation of automated direct sample introduction with comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry for the screening analysis of dioxins of fish oil. Journal of Chromatography A. 1201(1):69-77. Interpretive Summary: Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are among the most toxic compounds known, and these chemicals should be monitored in food and the environment to protect human health and the ecosystem. The current predominant method of analysis is too expensive and cumbersome, often taking $1,000 per sample and a full week of labor-intensive sample preparation. The common type of analytical instrument used for detection of PDCD/Fs is also very expensive, bulky, and requires an expert operator. In this research study, we evaluated comprehensive gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOF) as an alternative approach to lower costs and speed analysis of PCDD/Fs. This manuscript describes the development of sample preparation procedures to most efficiently analyze dioxins in cod liver oil using a novel injection approach for GC×GC-TOF. The approach is much more streamlined than the current methods, and achieves adequate detection limits for regulatory screening and fish oil process control applications. It may be useful to regulatory agencies and fish oil supplement makers worldwide.
Technical Abstract: An automated direct sample introduction technique coupled to comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (DSI-GC×GC/TOF-MS) was applied for the development of a relatively fast and easy analytical screening method for 17 polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and 4 non-ortho polychlorinated biphenyls (PCBs) in fish oil. Comparison of instrumental performance between DSI-GC×GC/TOF-MS and the traditional gas chromatographic high resolution mass spectrometric (GC-HRMS) method showed good agreement of results for test solutions analyzed in blind fashion. High tolerance of the DSI technique for lipids in the final extracts enabled a streamlined sample preparation procedure that only required gel permeation chromatography (GPC) and solid-phase extraction (SPE) cleanup with graphite carbon black. The maximum sample size for the method was 2 g of cod liver oil, which achieved limits of quantitation (LOQs) of 0.019 – 7.8 pg/g toxic equivalent quotients for the individual PCDD/Fs. Lower detection limits can be achieved by using larger sample size and scaling up the sample preparation procedure, but this adds to the labor, time, solvent consumption, and expense of the approach. Acceptable recoveries for nearly all analytes at 3 different spiking levels were achieved with good repeatability. This streamlined analytical screening method has the potential to monitor fish oil contaminated with dioxin and dioxin-like PCBs at or above current food safety limits.