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Accurate Structural Assignment Tool for PCBs Congeners, Using GC (front end) and Mass Spectrometric Ortho-Effects
Citation:
Osemwengie, L. Accurate Structural Assignment Tool for PCBs Congeners, Using GC (front end) and Mass Spectrometric Ortho-Effects. SETAC North America 42nd Annual Meeting, Virtual, NC, November 14 - 18, 2021.
Impact/Purpose:
This research evaluates a recently developed comprehensive 2-D GC coupled with a time-of-flight (TOF) mass spectrometer for the potential separation of 209 PCB congeners, using a sequence of 1-D and 2-D chromatographic modes. In two consecutive chromatographic runs, using a 40 m, Rtx-PCB column and a 1 m DB-17 column, connected in tandem, 196 PCB congeners are distinguished, including 43 of the 46 pentachlorobiphenyl isomers. Some of the chlorinated biphenyls that could not be resolved chromatographically are resolved with the use of the “ortho effect,” which distinguishes PCB isomers having 2,2¿-; and 2,2¿6- chlorine substitution from those isomers without these substitutions. The result of this work falls short of our goal of separating all 209 PCB congeners, but still provides investigators with a new tool for a better front-end separation of PCB-specific congeners, and potentially, for use in acquisition of more accurate data.
Description:
This study evaluates the use of comprehensive two-dimensional gas chromatography (2D-GC) coupled with a time-of-flight (TOF) mass spectrometer for the separation of 209 PCB congeners, using a sequence of 1D and 2D chromatographic modes. Some of the chlorinated biphenyls that could not be resolved chromatographically are resolved with the use of mass spectrometric “ortho effect,” which distinguishes PCB isomers having 2,2’-; and 2,2’6- chlorine substitution from those isomers without these substitutions. Commercially available standards permitted the test of all 209 PCB congeners for the mass spectrometric “ortho effect,” or the enhancement of the [M-Cl]+ ion abundance, relative to the molecular ion for biphenyls having 2,2'-; 2,2',6-; and to a smaller degree, 2,2',6,6'- chlorine substitution. Using chromatographic evidence, this study verified that much smaller “ortho effects” were observed for PCBs lacking any, or one ortho chlorine (2-), or two ortho chlorines on the same ring (2,6-). The result of this work potentially provides investigators with a combined new tool for a better front-end (GC column) and mass spectrometric separations of PCB-specific congeners, optimized for the acquisition of more accurate data.
