Supercritical Fluid Extraction and Cleanup with Capillary GC--lon Trap Mass Spectrometry for Determination of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans in Environmental Samples

Abstract

The optimization of an analytical process involving solvent-free isolation and full scan mass spectrometric quantitation for the determination of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) is presented and discussed. Supercritical fluid leaching and cleanup with Florisil™ is used to quantitatively remove the target analytes from environmental matrices and to eliminate interferences from the extraction mixture. This method is applied to analysis of solid samples such as fly ash and paper pulp and to aqueous matrices such as paper mill effluents, using an indirect supercritical fluid extraction approach. Gas chromatographic separation is performed on narrow-bore capillary columns. Separation and quantitation of the extract mixture is performed on capillary gas chromatography—mass spectrometry (GC—MS). A thin-film stationary phase (0.1 μm) has been found to yield superior resolution and analysis time as compared with a 0.25-μm film thickness column. Low cost quadrupole ion trap mass spectrometry is used to facilitate proper quantitation of eluting analytes. The full mass spectrum of pg levels of analyte obtained with this technique eliminates possible classification errors that might arise when only a few confirming ions are used, as with a conventional quadrupole mass spectrometer. In the proposed analytical procedures non-PCDD—PCDF isotopic internal standards, such as d₁₂-benzo(a)pyrene and non-¹³C-2,3,7,8 recovery surrogates such as ₁₃C-1,2,3,4-T₄CDD are used, so that the highly toxic 2,3,7,8-substituted PCDD may be confirmed by their full scan spectra.