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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.

Homolog Group

 

Number of Chrlorines

Monochlorobiphenyl

MCB

One Chlorine

Dichlorobiphenyl

DiCB

Two Chlorines

Trichlorobiphenyl

TrCB

Three Chlorines

Tetrachlorobiphenyl

TeCB

Four Chlorines

Pentachlorobiphenyl

PeCB

Five Chlorines

Hexachlorobiphenyl

HxCB

Six Chlorines

Heptachlorobiphenyl

HPCB

Seven Chlorines

Octachlorobiphenyl

OCB

Eight Chlorines

Nonachlorobiphenyl

NCB

Nine Chlorines

Decachlorobiphenyl

DCB

Ten Chlorines

The term Arcolor™ is a trade name from one of the major PCB producers.  An Aroclor is a mixture of PCB congeners.  The nine most common Aroclors include:

 

PCB Aroclors

 

PCB-1016

PCB-1242

PCB-1260

PCB-1221

PCB-1248

PCB-1262

PCB-1232

PCB-1254

PCB-1268

How Can TestAmerica Help You?

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, TestAmerica 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. 

PCB Analysis

Instrumentation

Method

PCB Aroclors

GC/ECD

EPA Method 8082

PCB Homologs

LRGC/LRMS

EPA Method 680

PCB Homologs

HRGC/HRMS

EPA Method 1668 (A or C)

PCB Congeners (Short List)

GC/ECD

EPA Method 8082

PCB Congener (209)

HRGC/HRMS

EPA Method 1668 (A or C)

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 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.

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.