Comparison of immunoassay and gas chromatography–mass spectrometry for measurement of polycyclic aromatic hydrocarbons in contaminated soil

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are frequently encountered in the environment and may pose health concerns due to their carcinogenicity. A commercial enzyme-linked immunosorbent assay (ELISA), was evaluated as a screening method for monitoring PAHs at contaminated sites. The ELISA was a carcinogenic PAH (C-PAH) RaPID assay testing kit that cross-reacts with several PAHs and utilizes benzo[ a]pyrene (BaP) as a calibrator. Soil samples were extracted with 50% acetone in dichloromethane (DCM) for analysis by ELISA and gas chromatography–mass spectrometry (GC–MS). The overall method precision was within ±30% for ELISA and within ±20% for GC–MS. Recovery data for spiked soils ranged from 46 to 140% for BaP as determined by ELISA. Recoveries data of the GC–MS surrogate standards, 2-fluorobiphenyl and chrysene, were greater than 70%. The GC–MS procedure detected a total of 19 priority PAHs (2–6-ring PAHs) including seven probable human carcinogens (4–6-ring B2-PAHs). The ELISA results were compared to GC–MS summation results for the total 19 target PAHs as well as for the subset of the seven B2-PAH compounds. For all soil samples, the PAH concentrations derived from ELISA were greater than the sum of B2-PAH concentrations obtained by GC–MS. ELISA determinations were also frequently greater than the results obtained by GC–MS for the total 19 PAH compounds. This discrepancy can be expected, since the ELISA is a screening assay for the detection of several related PAHs while the GC–MS procedure detects priority PAH compounds. Thus, only a subset of PAHs (e.g. 19 PAHs) in the soil samples were measured by GC–MS while additional PAHs, including alkylated PAHs, and PAH derivatives have been demonstrated to be cross-reactive in the C-PAH ELISA. Results of paired tests show that the PAH data from ELISA and GC–MS methods are significantly different ( P<0.001), but highly correlated. The ELISA data had a strong positive relationship with the GC–MS summation data for the B2-PAHs as well as for the 19 PAHs targeted by the GC–MS method. Results indicate that the ELISA may be useful as a broad screen for monitoring PAHs in environmental samples.