Field evaluation of an immunoassay for benzene, toluene and xylene (BTX)

A U.S. Environmental Protection Agency Superfund Innovative Technology Evaluation (SITE) demonstration of an immunoassay for benzene, toluene, and xylene (BTX) compounds was conducted at four field sites within Las Vegas Valley, Nevada. The BTX immunoassay was developed by Antox, Inc. (South Portland, ME) as a semiquantitative test designed as a screening technology for classifying samples as above or below 25 ng/g BTX (the decision level). The immunoassay is simple to use, rugged, inexpensive, and produces on-site results in about 30 min. On-site immunoassay results for aqueous field samples were compared to laboratory-based gas chromatography (GC) results. Compared to the confirmatory GC results, the field sample false negative rate was 6% and the false positive rate was 7%. The immunoassay performed well as a screening tool for samples with BTX concentrations above 200 ng/g, but was inconsistent near the claimed 25 ng/g decision level. However, a small modification to the evaluation protocol is shown to screen for samples below 25 ng/g. The immunoassay provides adequate information for monitoring decisions such as the initial characterization of pollution plume profiles or screening samples to identify either high or low BTX levels.