Citation:

Osemwengie, L. Achieving More Accurate PCBs Structural Assignment Using Gas Chromatography and Mass Spectrometry “Ortho Effects” for all PCB Congeners. 2023 SETAC North America Annual Meeting, Louisville, KY, November 12 - 16, 2023.

Impact/Purpose:

A method for the determination of polychlorinated biphenyls (PCBs) in caulk was developed; with application to a set of caulk and window glazing material samples. This method was evaluated by analyzing a combination of 47 samples of caulk, glazing materials, and including quality control samples, from older buildings in four locations in the United States. These samples were collected from the interior and exterior doors, windows, interior building seams, around installed fixtures and appliances, and within interior and exterior building joints. The choice of materials for testing the efficacy of this method, emanated from the use of caulk and glazing materials in older buildings in the United States. Quality control analysis showed a range of 45 to 170 % for spike recovery from the various samples, and a range of 10.9 to 20.1 % difference in precision. The result for the samples analyzed showed that three of the four locations sampled contained caulking and glazing materials with levels of PCBs in the range of 54.6μg/g to 445,000μg/g. Across the four locations, 24% of collected caulk and glazing material samples had elevated PCB levels relative to the U.S. EPA’s 50 μg/g criteria under the Toxic Substance Control Act. The PCBs determined in the samples, exhibited characteristic chromatographic patterns similar to those of Aroclor 1242, 1248, 1254, 1260, 1262, and a 1016/1254 mix.  

Description:

The availability of PCBs commercial standards and references provided an opportunity to test all 209 PCB congeners for their 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.  During the study, it was observed and verified that much smaller “ortho effects” were present for PCBs lacking any, or one ortho chlorine (2-), or two ortho chlorines on the same ring (2,6-). Chromatographic runs using a 40 meter, Rtx-PCB chromatographic column, connected orthogonally with a 1-meter DB-17 column, yielded retention properties which showed previously recognized chromatographic ortho effects and ring substitution – retention order correlations.  The order of elution was combined with the measured mass spectrometric “ortho effects” to test this premise as an additional tool for more accurate data acquisition and unambiguous structural assignment.

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