Final Decision to Certify Hazardous Waste Environmental Technology
The D TECH BTEX Immunoassay Test System (Benzene, Toluene, Ethylbenzene, Xylenes in Water and Soil) uses immunosorbent assay technology. It differs from other systems in that polyclonal antibodies are attached to latex particles and a non-enzyme color development procedure is used. BTEX in water is assayed directly; for soils, the system uses a methanol extract. The minimum detection limit of the D TECH system is defined as four standard deviations above zero concentration. At this reference level, the probability of avoiding false negative results is expected at the 99.9 percent confidence level. In recent runs of 30 samples each, no false negative results were observed with water and soil samples. Detection ranges are from 0.6 to 10 ppm for water and from 2.5 to 35 ppm for soil. Ranges can be extended upward by dilution of the extracts. The calibration of this product is based on a BTEX standard which consists of a pure mixture of benzene, toluene, ethylbenzene, and xylenes in a ratio of 4:55:8:33 (according to the relative proportion of BTEX compounds in a standard gasoline formulation proposed by U.S. EPA in 1988). The assay responds quite well to benzene with a cross-reactivity of 39 percent relative to the BTEX standard (100 percent). There is some cross-reactivity (5 to 11 percent) with naphthalene and polynucleated aromatics and little or no response to the alkanes tested.
The assay can be recalibrated in terms of other petroleum fuels with the option of developing appropriate conversion factors relative to the original calibration. Quantitation in this assay is by matching the color produced in the latex particles retained on a filter against a color card for a semiquantitative result. Alternatively, a numerical result can be read from the D TECTOR®, a hand-held, battery-operated meter.
Due to the high volatility of the constituents of BTEX, recovery and precision of the results from soils can vary significantly. The effect of soil type, moisture content, organic substances and interference at the site need to be taken into consideration when interpreting the results. Conditions for sample handling are important.
Strategic Diagnostics, Inc.
Newark, DE 19713
July 31, 1995
July 31, 1998
480 S. Democrat Road
Gibbstown, NJ 08027
Mr. Dwight Navis
Dr. Wolfgang Fuhs
File last updated: October 9, 1996