Analysis of foods and biological samples for dioxins and PCBs by high resolution gas chromatography—mass spectrometry

Abstract

Analysis of food and biological matrices for polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) by high-resolution gas chromatography and high-resolution mass spectrometry has developed rapidly in recent years. The understanding of relative toxicity of the various congeners has led to the development of selective and sensitive methods that are able to provide relevant data cost-effectively, and with a high level of quality assurance. The methods are based on stable-isotope dilution mass spectrometry with the mass spectrometer operating in the selected ion recording (SIR) mode, and have been developed into regulatory methods such as the USEPA methods 1613 and 8290. Key to the methods are the clean-up steps, where the matrix is concentrated while retaining the key analytes. Concentration factors of up to 1000 are obtained with analyte recovery generally exceeding 80%. Few new techniques have been developed for the clean-up of sample matrices; however, existing techniques have been automated successfully. Capillary gas chromatography columns have been improved, in both the design of the stationary phases and the robustness of the columns. However, full isomer-specific separation of all the 2,3,7,8-substituted PCDDs and PCDFs, and the co-planar PCBs, still requires the use of two columns. Effective compromise can be achieved with those columns designed specifically for dioxin analysis, especially for the separation of the tetrachlorinated dioxins and furans. High-resolution SIR mass spectrometry generally operates with 10000 resolving power, with some applications requiring up to 22000 resolving power. Modern data systems enable result calculations to be readily made, with significant increases in quality assurance data being achieved at the sub-picogram per gram (parts per trillion, ppt) level.