Figure 5. Correlation of calculated TCDD TEQs for GC/MS data with measured TCDD TEQs using the P450RGS assay

Technical Note DOER-C8

July 1999

Figure 5. Correlation of calculated TCDD TEQs for GC/MS data with measured TCDD TEQs using the

P450RGS assay (A) or the EROD assay (B) on 15 SA/SG-cleaned miscellaneous sediment

extracts (Means of six replicates SD)

the GC/MS data was 0.658 (Figure 5B). Comparison of the six sediment extracts with detectable

activity by both assays gave a correlation of 0.457 (Figure 6). As with the NYDMMP sediments,

the P450RGS assay gave a higher response (about 2-fold) than did the EROD assay.

Interlaboratory Comparison of the P450RGS Assay. Splits of the NYDMMP sediment

extracts were also analyzed by CAS in order to compare the reproducibility of results using the

P450RGS assay. CAS performed the assay using only three replicates of each sample, whereas six

replicates were analyzed at the U.S. Army Research and Development Center, Waterways Experi-

ment Station (WES). The interlaboratory comparisons are shown in Figures 7 and 8 (crude and

cleaned extracts, respectively). The correlation coefficients show that the results obtained by the

two laboratories were very similar.