Comprehensive two-dimensional gas chromatography thermodynamic modeling and selectivity evaluation for the separation...

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful tool for complex separations. The selectivity and sensitivity benefits from thermally modulated GC×GC were applied to the analysis of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Thermodynamic indices of 50 PCDD/Fs, including the 17 toxic 2378-substituted congeners, were collected and used to model one-dimensional and two-dimensional separations with the Rtx-Dioxin2 and Rxi-17SilMS capillary GC columns. Thermodynamic modeling was used to determine the optimal conditions to take advantage of the selectivity differences between the Rxi-17SilMS and Rtx-Dioxin2 to separate all PCDD/Fs congeners from the 2378-substituted compounds by GC×GC. The modeled elution order patterns closely matched the experimental elution order in 40 of the 45 tetrachlorinated through hexchlorinated compounds analyzed. The heptachlorinated and octachlorinated congeners were not included in the elution order modeling as they are readily resolved from other dioxin congeners. The Rxi-17SilMS crossed with the Rtx-Dioxin2 was able to separate all 2378-substituted compounds in a single separation in a fish matrix. Thirty-three additional PCDD/F congeners were added to the fish matrix that coelute with the 2378-substituted congeners. The Rxi-17SilMS crossed with the Rtx-Dioxin2 was able to fully resolve 11 of the 2378-substituted congeners with the other six congeners exhibiting coelutions with only one other congener.