PCB Congeners by Low-Resolution GC-MS - Method 1628 (Not yet approved)

Method 1628 measures polychlorinated biphenyls (PCBs) in wastewater. This method is not yet approved at 40 CFR Part 136.

On this page:

Background
Multi-laboratory Validation Study
Description of Method
Conclusions
Status
Documents

Background

The only method currently approved at 40 CFR Part 136 for monitoring PCBs in wastewater is Method 608.3, which only targets seven common Aroclor mixtures. Because most PCB contamination in the environment is highly weathered and often does not resemble any of the Aroclor mixtures and there are non-Aroclor sources of PCB in the environment, Aroclor results are likely to underestimate PCB contamination or provide non-detects in a sample when compared to the analysis of individual PCB congeners. EPA sought to develop a new method that would meet the following goals:

Identified and quantified PCBs using individual congeners, not Aroclors
Was more sensitive than Method 608.3, but not so sensitive that it is susceptible to background contamination issues
Could be implemented at a typical mid-sized full-service environmental laboratory.

Multi-laboratory Validation Study

In 2020, the EPA’s Office of Water completed a multi-laboratory validation of Method 1628, a PCB congener method using low-resolution gas chromatography - mass spectrometry with selected ion monitoring (GC-MS-SIM). The study involved 12 laboratories and 4 matrices. EPA has developed a multi-laboratory validation study report and accompanying method.

Description of Method

Method 1628 detects all 209 PCB congeners and quantifies them either directly or indirectly. A total of 29 carbon-13 labeled PCB congeners are used as isotope dilution quantification standards. An additional 19 congeners are quantified by an extracted internal standard procedure, using one of the isotope dilution standards. The remaining 144 congeners are quantified against a labeled standard in the same homolog. This approach strikes a balance between enabling the laboratory to detect and quantify all 209 congeners, while not making the method too arduous. Method performance was similar across all the congeners, regardless of the quantification approach.

The primary focus of this new method is on wastewater compliance monitoring, but there is a need for testing biosolids, soils/sediments, and fish tissue as well. Therefore, the multi-laboratory study tested:

Nine aqueous sample types, including wastewater effluents and influents collected from publicly owned treatment work and indirect industrial dischargers
Three sediments
Three biosolids collected from municipal wastewater treatment plants
Fish tissues from three species.

Conclusions

The EPA met its goals and has demonstrated that Method 1628 is effective in all the matrices tested. It provides better quality control information to support data quality assessments, is more sensitive than the currently approved Method 608.3, but not so sensitive that blank contamination is a problem, and can be easily implemented at a typical full-service environmental laboratory. The EPA’s only other PCB congener method uses high-resolution mass spectrometry instrumentation, which many full-service laboratories do not own. Therefore, Method 1628 provides access to PCB congener analysis to any laboratory using a typical gas chromatograph/mass spectrometer (GC/MS) instrument that is used for many other EPA methods.

Status

Method 1628 is not yet approved at 40 CFR Part 136 for use in Clean Water Act compliance monitoring. The method would need to be proposed and promulgated in a future rulemaking to become an approved method. However, having completed a multi-laboratory validation study, the EPA considers the method suitable for release to laboratories, regulators, regulated industries, and the general public. States authorized to issue NPDES permits may elect to use this method in permits, pending nationwide approval by the EPA.