Summary

SGS has developed and validated accurate, sensitive and accessible polychlorinated biphenyls (PCBs) analysis by GC-MS in support of the US EPA’s initiative to update the PCB measurement strategy for the National Pollutant Discharge Elimination System (NPDES) permit program.

Background

Polychlorinated Biphenyls (PCBs) are ubiquitous contaminants regulated under the US Clean Water Act. Currently, the only promulgated method for PCBs is EPA Method 608.3 which measures 7 common Aroclor mixtures. This approach has several issues including poor sensitivity, inability to deal with the aging/weathering of aroclor mixtures in the environment, and inability to detect non-aroclor PCBs such as PCB-11. Analyses that measure PCB congeners, or that report PCB homolog totals are well known to be more accurate and more representative. A US EPA Region 4 report by Wischkaemper et al. 2013¹ details many of these issues. Figure 1 shows comparative data for two different sample sets of soils.

In many of these cases (especially sample set 2), aroclors underestimate homolog totals by orders of magnitude. In some cases (sample set 1), there is a mixture of under- and over-prediction as aroclor patterns overlap individual PCB congeners and can double-count PCB totals.

EPA method 1668, a GC-HRMS method (initially developed and validated by SGS AXYS) is a sensitive and specific method for congener analysis and total PCBs and has been offered by SGS AXYS, SGS Wilmington and a handful of specialty laboratories for a while now. However, its relative complexity, instrumentation needs, and very high sensitivity makes it difficult to implement in a typical full service laboratory dealing with discharge permitting and other regulatory needs. To fill this gap between aroclor methods and congener-specific methods, the US EPA started a process to validate a GC-MS method for 209 PCB congeners in wastewater and other matrices to eventually replace monitoring by legacy Aroclor-based methods.

Method Validation Objectives and Results

The criteria the US EPA set for this validation were as follows:

1. Identify and quantify PCBs using individual congeners, not Aroclors,
2. A method more sensitive than Method 608.3, but not too sensitive to be affected by laboratory background and
3. Can be implemented at a typical mid-sized full-service environmental laboratory with access to single-quadrupole GC-MS instruments.

The single lab validation process at SGS AXYS was very successful in water, solids and tissue, and all objectives were met. Adrian Hanley of the US EPA Office of Water presented results at the National Environmental Monitoring Conference (NEMC 2019)². The presentation is embedded below and shows excellent validation data generated by SGS AXYS. (Click here if you are not able to see the embed)

Since this presentation, the multi-laboratory validation process is almost complete and the SGS specialty laboratory in Wilmington has also completed all validation protocols successfully.

Method Attributes

1. Extraction and cleanup methods for water, solids and tissue
2. Analysis by GC-MS
3. Quantitation of all 209 congeners (167 peaks) using
   1. 23 congeners by isotope-dilution, 6 by isotope dilution with 8 coeluters
   2. 19 congeners by extracted internal standard (EIS) surrogate quantification
   3. All other 144 congeners quantified indirectly
4. MDLs
   1. Aqueous – 0.2-3 ppt, compared with a typical Method 608.3 detection limit of >60 ppt
   2. Solis – 3-91 ppt
   3. Tissue – 97-2100 ppt

Conclusion

While SGS AXYS has performed PCB congener analysis for 30+ years, we’re looking forward to this approach being accessible to the multitude of laboratories measuring samples for NPDES permits and other applications. Please contact us for more details on this approach.

References