PCBs and Formaldehyde

Polychlorinated Biphenyls (PCBs)

PCB Aroclors, Congeners and Homologs

Polychlorinated Biphenyls (PCBs) are a class of organochlorine compounds that were commercially produced for a wide variety of uses in the 1900’s. Their chemical properties and physical stability led to wide spread commercial use as dielectric and coolant fluids in electrical equipment and in heat transfer fluids. Because of their stability, they are considered a persistent organic pollutant.  PCB production was banned by the United States in 1979.

PCB is not a specific compound but a group of compounds. PCB nomenclature can be complicated because PCBs were produced as complex mixtures of various chemical compounds (congeners). There are 209 discrete congeners with 1 to 10 chlorine atoms attached to a biphenyl.

When the congeners are grouped by chlorination level, each of these groups is referred to as a homolog. There are 10 homolog groups.

One of the challenges associated with PCBs is determining the type of analysis that may be required. Projects can require total PCBs, 7 or 9 PCB Aroclors, PCB Homologs, 209 individual PCB Congeners, co-planar PCB Congeners or other program specific lists of PCB Aroclors or Congeners. Oftentimes, the regulatory framework can define the specification for the PCB analysis, or it can be defined based on the end use of the data or even the environmental matrices being analyzed. No matter which PCB analysis is required, Eurofins can support your project’s PCB analytical requirements.

There are many gas chromatography (GC) methods for the determination of PCBs. One of the variations in PCB analysis is the choice of the analytical detector, including an Electron Capture Detector (ECD), Mass Spectrometer (MS) or a High Resolution Mass Spectrometer (HRMS). Historical methods using GC/ECD instrumentation (8082) have generally determined PCBs as Aroclors. Methods using GC/MS or HRGC/HRMS instrumentation (1668) are capable of selective determination of PCB Homologs and the comprehensive determination of PCB Congeners.

US EPA SW 846 Method 8082 routinely provides for the assessment of PCBs as either Arcolors or subsets of congeners when proper consideration is given to the impact of co-elutions. The GC/ECD method provides good sensitivity. However, it is not well applied to the analysis of samples containing complex mixtures of Aroclors, degraded Aroclor patterns, or those having high backgrounds of GC/ECD responsive constituents.

US EPA Method 680 is a LRGC/LRMS method for PCBs that utilizes selected ion monitoring (SIM) for improved sensitivity and better specificity than Method 8082. The method is typically used for PCB Homologs and Total PCBs for a variety of environmental matrices including those containing non-PCB related signals that cannot be resolved by Method 8082. Since this technique employs GCMS for spectral identification for targeted PCBs, the method is less prone to non-PCB related interferences which could result in a high biased PCB value. Method 680 is designed to provide for increased precision over the GC/ECD (8082) method and be more cost conscious than Method 1668.

US EPA Method 1668 (A or C) is an HRGC/HRMS method that provides for an assessment of individual congeners, which can also be summed for homolog totals. The method provides for a definitive assessment of PCBs based on highly resolved mass spectral identification, with sensitivity approaching two orders of magnitude lower than the GC/ECD method. However, this sensitivity can be much greater than is needed for PCB-impacted media.