Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
A demonstration of technologies for determining the presence of dioxin and dioxin-like compounds in soil and sediment was conducted under the U.S. Environmental Protection Agency’s (EPA’s) Superfund Innovative Technology Evaluation Program in Saginaw, Michigan, at Green Point Environmental Learning Center from April 26 to May 5, 2004. This innovative technology verification report describes the objectives and the results of that demonstration, and serves to verify the performance and cost of the Abraxis LLC Coplanar PCB Enzyme-Linked Immunosorbent Assay (ELISA) Kit. Four other technologies were evaluated as part of this demonstration, and separate reports have been prepared for each technology. The objectives of the demonstration included evaluating the technology’s accuracy, precision, sensitivity, sample throughput, tendency for matrix effects, and cost. The test also included an assessment of how well the technology’s results compared to those generated by established laboratory methods using high-resolution mass spectrometry (HRMS). The demonstration objectives were accomplished by evaluating the results generated by the technology from 209 soil, sediment, and extract samples. The test samples included performance evaluation (PE) samples (i.e., contaminant concentrations were certified or the samples were spiked with known contaminants) and environmental samples collected from 10 different sampling locations.
The Abraxis LLC Coplanar PCB ELISA Kit is an immunoassay technology that reports the total toxicity equivalents (TEQ) of coplanar polychlorinated biphenyls (PCBs) in the sample. As part of the performance evaluation, the technology results were compared to TEQ results generated by a reference laboratory, AXYS Analytical Services, using EPA Method 1668A. It should be noted that this technology may not directly correlate to HRMS TEQPCB in all cases because it is known that the congener responses and cross-reactivities to the kit are not identical to the World Heath Organization toxicity equivalency factors that are used to convert congener HRMS concentration values to TEQPCB. The effect of cross-reactivities may contribute to this technology reporting results, which are biased high or low compared to HRMS TEQPCB results. Therefore, the Abraxis kit should not be viewed as producing an equivalent measurement value to HRMS TEQPCB but as a screening value to approximate HRMS TEQPCB concentration. It has been suggested that correlation between the Abraxis TEQPCB results and HRMS TEQPCB results could be improved by first characterizing a site and calibrating the Abraxis results to HRMS results. Subsequent analysis using the Abraxis kit for samples obtained from this site may then show better correlation with the HRMS TEQPCB result. This approach was not evaluated during this demonstration.
The Abraxis kit reported data higher and lower than the certified PE values. Abraxis generally reported data that were higher than the reference laboratory TEQPCB values, with the exception of ultra-high level PCB samples [> 10,000 picogram/gram (pg/g) TEQ] where Abraxis reported values lower than the reference method. The technology’s estimated MDL was 6 to 31 pg/g TEQPCB; the developer’s reporting limit was 6.25 pg/g TEQPCB. No statistically significant matrix effects on precision were observed by sample type (performance evaluation vs. environmental vs. extract), matrix type (soil vs. sediment vs. extract), or polynuclear aromatic hydrocarbon (PAH) concentration. One result (5% of total) from replicate sample sets that were analyzed in the laboratory and in the field showed a significant statistical difference, but the one sample was a PE sample that was spiked with only PAHs and no PCBs. The kit had a false positive rate of 35% and a false negative rate of 7% around 6.25 pg/g TEQPCB (the reporting limits of the technology). Abraxis reported significantly fewer false positives (8%) and false negatives (3%) around 50 pg/g TEQPCB. This evaluation indicates that the Abraxis kit could be an effective screening tool for screening sample concentrations above and below 50 pg/g TEQPCB, particularly considering that the cost ($22,668 vs. $184,449) and the time to analyze the 209 demonstration samples were significantly less than those of the reference laboratory.