Improvement and application of an immunoassay for screening environmental samples for dioxin contamination

Abstract

We previously had developed monoclonal antibodies for the immunoassay of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF), and have since refined the use of these antibodies for the detection of dioxins in a wide range of contaminated samples, with the aim of developing a screening assay for dioxin contamination. The levels of PCDD and PCDF contamination in 13 different samples, including fly ash, soil, technical-grade chemicals, motor oils, polychlorinated biphenyl transformer oil and still-bottom residues, were determined by immunoassay. The contamination ranged from less than 1 to several thousand ppb PCDD and PCDF. The levels of PCDD and PCDF contamination in some samples were determined by conventional GC-MS. The monoclonal antibodies used in this study detect many of the tri-, tetra- and pentachloro congeners of PCDD and PCDF, while the GC-MS data included information on total tetra- and pentachloro congeners of PCDD and PCDF, as well as levels of specifically regulated toxic congeners. There were good correlations between the results of the immunoassay and those of conventional GC-MS analysis, in spite of the differences in the exact congeners detected by the two techniques. There were no false-negative results. Moreover, the immunoassay required substantially less sample cleanup than did GC-MS, thus offering the promise of greatly reduced costs and time for screening samples. Only the soil matrix interfered with results; the cleanup methods for this matrix still need improvement.