Separation of 2378 Tcdd, 2378 Tcdf, 23478 Pecdf, and Other 2378 Pcdds and Pcdfs on a New High-temperature Gc Column

Introduction EPA Methods 1613 (Tetrathrough Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS) and 8290a [Polychlorinated Dibenzodioxins(PCDDs) and Polychlorinated Dibenzofurans (PCDFs) By High Resolution Gas Chromatography/High Resolution Mass Spectrometry (HRGC/HRMS)] specify the use of a 60m 5% diphenyl 95% dimethyl polysiloxane GC column (e.g. DB-5, Rxi-5ms) for 2378 TCDD isomer specificity. This column does not separate 2378 TCDF or 23478 PeCDF, or even 123478 HxCDF. In a recent analysis of sediment, river clay, soil, and fly ash samples by the Ontario Ministry of Environment, these three furans summed represented 17 to 69% of the TEQ (dioxins/furans) depending on the sample. 23478 PeCDF contributed 9 (sediment) to 30% (fly ash) of the TEQ, but the value is biased high since there are multiple coelutions for 23478 PeCDF on 5-type columns (this includes silphenylene types such as DB-5MS and Rxi-5Sil MS) as reported by Slava Fishman with colleagues Greg Martin and Michael Wilken in their Chemosphere paper, “Retention time profiling of all 136 tetrathrough octachlorinated dibenzo-p-dioxins and dibenzofurans on a variety of Si-Arylene gas chromatographic stationary phases”. For 2378 TCDF, the EPA Method recommends a 225 or 2330 or 2331 GC column, high cyano content stationary phases that will also separate 23478 PeCDF and 123478 HxCDF. Unfortunately, these cyano columns all have very low maximum operating temperatures of 240-275°C, show high bleed, and are not rugged.