Method B is based on the results of an interlaboratory validation study, and a peer review of that study. The Method was developed for use in wastewater, surface water, soil, sediment, biosolids and tissue matrices. Other applications and matrices may be possible, which may or may not require modifications of sample preparation, chromatography, etc. The detection limits and quantitation levels in this Method are usually dependent on the level of interferences and laboratory background levels rather than instrumental limitations.
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This study was conducted in to validate the performance of EPA Method A in municipal wastewater, fish tissue, and biosolids matrices.
EPA used the results of the study to evaluate and revise Method A quality control QC acceptance criteria for initial precision and recovery, ongoing precision and recovery, and labeled compound recovery from real world samples. EPA acknowledges the volunteer laboratories that participated in the study and, in particular, those laboratories that took the extra effort to comment on EPA Method A and to provide suggestions for improvements.
Disclaimer Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Contacts Richard Reding, Ph. Concentration for Wastewater 15 4. Concentration for Tissue 16 4. Quality control QC acceptance criteria for initial precision and recovery, ongoing precision and recovery, and labeled compound recovery from real world samples are in Table of this report.
These PCB-congeners are the individual chemicals that comprise a class of pollutants known as Aroclors. Additional background on the nature and determination of PCBs and on the history of development, validation, and peer-review of EPA Method A is in the study plan.
The changes corrected technical and typographical errors and reflected practice of the method by laboratories based on comments received. The August revision was used for the study and is the revision distributed by EPA at the time of writing of this report. Since that presentation, the results have been further evaluated and presented in this report. Therefore, this report supersedes any material previously presented or published.
To allow for some loss of data due to error, lost samples, outlier removal, or other unforeseen causes, EPA included 14 participant laboratories in the study. The study design is detailed in an appendix to this report. The intent was to ensure that Study participants already possessed the facilities, equipment, and trained staff necessary to implement the method.
Fourteen 14 volunteer laboratories were selected to participate in this study. The laboratories were notified of their selection at least two weeks before the study began, so that they would have time to review the method and study-specific instructions. Of the 14 laboratories selected, 11 were commercial laboratories and 3 were EPA Regional laboratories. Laboratories were not required to validate the method in all three matrices; as a result, the number of participant laboratories varied, depending on the matrix tested.
As discussed in section 3 of this report, because of scheduling problems 3 of these 14 volunteer labs did not submit data. To offset costs to the laboratories, EPA provided each laboratory with a set of analytical standards necessary to identify and measure the PCB congeners targeted by Method A. EPA also provided the laboratories sets of standard solutions containing native and carbon labeled compounds necessary to calibrate their instruments and to conduct all analyses.
Laboratories were provided with detailed instructions for combining and diluting standards to preclude injudicious use of standards. The instructions were based on procedures given in Method A. In addition to the 14 volunteer participant laboratories, a sample processing laboratory was contracted to perform all activities necessary to ensure that the participant laboratories received homogenized, spiked, and aliquoted samples. November Method A Interlaboratory Validation Study prepare replicate samples for analysis by participant laboratories.
The participant and sample processing laboratories are listed in Table While results obtained by individual laboratories were used relative to this purpose, no attempt was made to assess performance of individual laboratories. No endorsement of these laboratories is implied, nor should any be inferred.
To preserve confidentiality, laboratories that volunteered for this study, including three that did not submit lab data, were assigned numbers randomly from 1 to The lab identities and that of the sample processing laboratory are not revealed in the data or lists in this report.
EPA provided existing archived fish tissue and biosolids samples to the sample processing laboratory to prepare Study samples representing these matrices. No archived sample volume was available for wastewater, therefore, the sample processing laboratory prepared the wastewater samples. These samples had been stored in freezers at an EPA sample repository. So that a sufficient amount of each sample was available to support the study, EPA identified several samples of each matrix type that could be combined to produce large volumes of Youden pairs with the desired congener distribution.
Youden pairs are defined as two samples of the same matrix containing similar, but not exact, concentrations of the analytes of interest. Once these stored samples were identified, they were forwarded on ice to the sample processing laboratory.
Although PCBs are stable and do not require preservation, ice was used to prevent decomposition offish tissue and to retard gas production in the biosolids. For wastewater, amounts of effluent grab samples were collected from a publicly owned treatment works POTW that were sufficient to provide enough samples for all of the participant November Method A Interlaboratory Validation Study laboratories, and excess sample in case of breakage, spillage, or other problems.
Bulk wastewater was collected in polyethylene carboys and shipped overnight to the sample processing laboratory for spiking and distribution.
This eliminated concerns about how well spiked constituents would be incorporated into these matrices and whether spiked samples were representative of real-world samples. The goal of the mixing and aliquoting scheme for biosolids and tissues was to obtain Youden pairs for each matrix of interest i. Because the available "excess" volumes of the biosolids and fish tissues were limited and the number of laboratory participants was relatively large, the Youden pairs were prepared in a multi-step process.
For the biosolids, the first step was to combine and homogenize five biosolids samples to form a composite. This composite was then divided approximately in half.
One half of the composite was designated as biosolids sample "A" while the other half was used to prepare biosolids sample "B. The composite was then divided approximately in half, with one half being designated as tissue sample "A. The sample processing laboratory was required to perform background and homogeneity analyses of both the biosolids and tissue matrices.
The laboratory was instructed to analyze one g dry weight aliquot of sample "A" as the background analysis, and two g dry weight aliquots of sample "B" as the homogeneity aliquots for both the biosolids and tissue matrices. Because of the mixing scheme for both of these matrices, it was assumed that if the homogeneity for sample "B" is found to be acceptable, the homogeneity of sample "A" would also be acceptable.
This approach was used to preserve sample mass. Results of tissue and biosolids background and homogeneity analyses are discussed in Section 4. Thus, the sample processing laboratory was instructed to first analyze an aliquot of wastewater from a publicly owned treatment works POTW to determine background PCB congener levels.
Following a review of the background results by SCC, EPA defined the spiking levels, and provided the sample processing laboratory with detailed instructions to divide the unspiked POTW matrix into the required number of aliquots and spike each aliquot separately rather than spiking a bulk volume of wastewater and then subdividing the spiked sample into replicate aliquots to the appropriate concentrations.
Spiking each aliquot separately avoids problems with "wall effects," whereby organic pollutants spiked into a bulk November J Method A Interlaboratory Validation Study sample tend to adhere to the walls of the container, making it difficult to divide a bulk sample into multiple aliquots containing the same analyte concentrations. Because of the difficulty that would be encountered in preparing custom spiking solutions, wastewater samples were spiked with varying amounts of "individual native CB congener solutions" A2 through E2 listed in Table 4 of EPA Method A.
Concentrations of the congeners in the wastewater samples, by level of chlorination, are given in Table Results of the homogeneity analyses are discussed in Section 4.
After the aliquots were prepared, the sample processing laboratory labeled each sample container and cap with the corresponding unique sample number. The sample processing laboratory then shipped the prepared, numbered samples to the participant laboratories via air courier. Although PCBs are persistent, and thus do not require preservation, biosolids and tissue samples were shipped on ice to hinder decomposition of the tissues and gas formation in the biosolids.
The sample processing laboratory notified SCC of the shipping date, and SCC notified participant laboratories of the shipping and scheduled arrival dates. Table lists the numbers of wastewater, biosolids, and tissue samples that were prepared for distribution to the 14 participant laboratories. Because study results were to be used to evaluate or further develop QC acceptance criteria, laboratories were prohibited from performing multiple analyses to improve results.
Laboratories were, November Method A Interlaboratory Validation Study however, allowed to implement corrective action and reanalyses for QC failures attributable to analyst error, instrument failure, or identified contamination.
Laboratories were required to submit electronic and hard copies of summary sample results, and hard copies of all supporting raw data, run chronologies, chromatograms, example equations, and case narratives to SCC for review and data validation. Additionally, laboratories were asked to provide a detailed narrative describing any problems or recommendations and a description of any modifications to procedures specified in the method.
All submitted data were reviewed against the study and method requirements prior to use for evaluation of method performance. Discussions with this laboratory revealed no attempt to analyze a g sample. Their general experience has been that using a g sample results in difficulties during instrumental analysis lock-mass problems. Two laboratories 4 and 10 did not submit biosolids data because of difficulties encountered with clean-up and analysis.
Both of these laboratories attempted analyses on g samples, as suggested in the method. Laboratory 4 reported difficulties with the cleanup of both the biosolids samples. In one of the biosolids samples, upon the first acid wash, the sample appeared black in color and the phases could not be distinguished. The laboratory proceeded with the addition of sodium chloride in an attempt to mitigate the problem. During the subsequent acid wash steps second, third and fourth no color appeared in the aqueous layer.
The extract layer contained suspended particles and had a tar-like appearance and viscosity. In the case of the second biosolids sample, an emulsion resulted during back-extraction with base Section The laboratory unsuccessfully attempted to break the emulsion by adding sodium chloride and cooling, and tried diluting the extract with sodium chloride solution and hexane, followed by hexane rinses, and addition of sulfuric acid.
The extract was drained into a round bottom flask and concentrated by heating mantle. The sample was then washed with the maximum number 4 of acid washes suggested in the method. Laboratory 10 reported difficulties with the cleanup and extraction of both biosolids samples and reported that, despite having made two separate attempts to cleanup and extract the biosolids samples, they were not able to obtain reportable results.
The samples were initially extracted using approximately 22 grams of each sample dry weight basis. A total of six cleanup steps were applied to each sample. According to the laboratory narrative, even after these measures, the final extracts contained significant amounts of white crystals.
The remaining liquid portions of the extracts were separated from the crystals and injected. These extracts did not yield reportable results. The laboratory attempted to extract the samples a second time, this time using 2 grams each. Two cleanup steps were applied to these samples. No crystals were present in the final extracts; however the laboratory was still unable to obtain reportable results.
Laboratories 7 and 12 reported biosolids results on a wet weight basis whereas laboratories 8 and 13 reported biosolids results on a dry weight basis. The dry weight data for laboratory 8 were corrected to wet weight based on percent solids data provided by laboratory 8 Because laboratory 13 did not provide percent solids data, the laboratory 13 dry weight data were corrected to wet weight based on the mean of the percent solids data provided by the: sample preparation laboratory, laboratory 2, and laboratory 8.
These three laboratories were the only labs that provided percent solids data The laboratory narratives suggest that many laboratories lacked experience extracting and cleaning up a biosolids matrix. The resulting deviations from the method and study-specific instructions for analysis of biosolids samples by different laboratories resulted in some unusable and inconsistent data.
Thus, EPA excluded some biosolids results, as described in Section 3 of this report.
EPA Method 1668B
After extraction, a labeled cleanup standard is spiked into the extract which is then cleaned up using appropriate chromatographic procedures e. After cleanup, the extract is concentrated. Immediately prior to injection, labeled injection internal standards are added to each extract and an aliquot of the extract is injected into the gas chromatograph. Quantitative analysis is performed in one of two ways specified in the method using selected ion current profile SICP areas.
Clean Water Act Analytical Methods
EPA Method 1668 Revision A
EPA Method 1668A