This method is used for the determination of polychlorinated biphenyls (PCBs) at low levels from water samples 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 using grab sampling techniques. If there is residual chlorine in the sample, add 80mg of sodium thiosulfate per L of sample and adjust the pH to 2-3 with sulfuric acid. Use amber glass 1L bottles if possible for collection since the method requires the samples be protected from light.
Samples are typically extracted with methylene chloride. The extraction procedure can vary based upon the amount of solids present in the sample. If the sample contains <1% solids, then the sample can be extracted per normal procedures. If there is >1% solids in the sample, then the method calls for the extraction of an equivalent of 10g of solids. Keep in mind that this is a performance based method so lab procedures may vary.
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.
NOTE: This method is an update of and replaces Methods 1668, 1668A and 1668B.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | The method states that samples are good for up to one year if properly preserved, kept in the dark and at <6 °C. |
| Preservatives: | Keep samples in the dark. Adjust pH to 2-3 with sulfuric acid. If residual chlorine is present, add 80mg of sodium thiosulfate per L of sample. |
| Required Preps: | 1L Amber glass bottle with Teflon-lined lid |
| Collection Method: | Grab sampling |
| Analytical Methodology: | HR GC/MS |
| Documentation: | 
1668C
|
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.