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, toluen e, 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 sc reening technology for classifying samples as above or below 25 ng/g B TX (the decision level). The immunoassay is simple to use, rugged, ine xpensive, and produces on-site results in about 30 min. On-site immuno assay results for aqueous field samples were compared to laboratory-ba sed gas chromatography (GC) results. Compared to the confirmatory GC r esults, the field sample false negative rate was 6% and the false posi tive rate was 7%. The immunoassay performed well as a screening tool f or samples with BTX concentrations above 200 ng/g, but was inconsisten t near the claimed 25 ng/g decision level. However, a small modificati on to the evaluation protocol is shown to screen for samples below 25 ng/g. The immunoassay provides adequate information for monitoring dec isions such as the initial characterization of pollution plume profile s or screening samples to identify either high or low BTX levels. (C) 1997 Elsevier Science Ltd.