Method 1668C Air
Polychlorinated Biphenyls (PCBs) in Stationary Source Emissions
This method is used for the determination of polychlorinated biphenyls (PCBs) at low levels from stationary source emissions using isotope dilution HRMS (high resolution mass spectrometry). All 209 individual PCBs are determined as well as the Totals for each congener group (e.g. Total Mono-PCB, Total Di-PCB). Special interest is paid to the twelve PCBs designated by the World Health Organization (WHO) as the most toxic. This subset of PCBs may also be called the co-planar or dioxin-like PCBs. It is not currently possible to separate each of the 209 PCBs and some are reported as co-eluting compounds.
Samples are collected isokinetically using a modified Method 5 train which consists of a glass fiber filter containing no organic binders, XAD-2 resin trap, and a series of water impingers. The sampling train is rinsed with acetone and/or methylene chloride. The rinses and impinger water are collected and sent to the laboratory for extraction and analysis.
Typically all components of the train, including the rinses, are extracted and combined to produce one extract for analysis which represents the entire sampling train. This extract is then split and 50% of the extract is archived in case there are problems and re-analysis is necessary. The sample extracts undergo an extensive cleanup prior to analysis in order to remove interferences (dioxins, pesticides, PAH, etc.) in order to achieve the low limits of detection. If there are problems with the cleanup, the archived portion of the sample extract can be processed avoiding the need to resample.
Note that Method 1668A was developed by EPA's office of Science and Technology for the analysis of water, soil, sediment, biosolids, tissues and other matrices. It does not specifically reference air matrices but it is a performance based method. This is the method chosen for compliance projects because of it's specificity and low limits of detection.
NOTE: This method is an update of and replaces Methods 1668, 1668A and 1668B.