Relative performance of immunochemical (Enzyme-linked Immunosorbent Assay) and gas chromatography–electron-capture detection techniques to quantify polychlorinated biphenyls in mussel tissues

Abstract

Results from polychlorinated biphenyls (PCB) analyses of mussel tissue extracts by immunoassay (PCB RaPID Assay®) and conventional gas chromatography–electron-capture detection (GC–ECD) are described and compared. Mussels from natural populations with diverse concentrations of PCBs, mussel tissue fortified with technical Aroclor® 1254 and a certified reference material are included.A strong correlation is reported between “total” PCBs quantified by both techniques (r2 = 0.95, n = 27). Immunoassay results, however, exhibited lower values compared to GC–ECD, particularly when GC results are corrected for procedural recovery. A reduced antibody response, due to differences in the congener composition between the mussel extracts and Aroclor® 1254 (used to raise and calibrate the ELISA), provides the most likely explanation for this difference. Non-parametric statistical analyses confirmed that,although differing from Aroclor® 1254, PCB congener compositions in the mussel extracts most closely resemble that of Aroclor® 1254. At very high PCB concentrations (>30 g g−1 dry weight), however, ELISA results are statistically different (P < 0.01) from GC–ECD results, which is likely to be related to the solvation capacity of ELISA diluent. Similarity analysis showed high correlations between the most prominent congeners in Aroclor® 1254 and immunoassay results. This analysis did not, however, identify a specific chlorine substitution pattern to which the immunoassay preferentially responded. Whilst GC–ECD affords the capability to quantify individual congeners of different reactivity and toxicity, the data reported do indicate that immunoassay offers a rapid and inexpensive alternative method for estimation of “total” PCBs at environmental significant levels. It is, however, necessary to remove extraneous lipids to reduce matrix effects in the immunoassay.