Final Decision to Certify Hazardous Waste Environmental Technology
Ohmicron Total BTEX RaPID Assay®
(Semi-quantitative Assay of Petroleum Hydrocarbons in Water and Soil)
Certification No: 95-01-011
The Ohmicron BTEX RaPID Assay® system uses enzyme- linked immunosorbent assay (ELISA) technology. It differs from other systems in that polyclonal antibodies are attached to magnetic particles. BTEX in water is assayed directly; for soils, the system uses an extract in 75% methanol containing calcium chloride. Contamination with BTEX is expressed as above or below a specified target concentration. Ohmicron suggests using a site-specific reference material for calibration; target concentrations should be action or decision levels appropriate for the local situation.
Provided that the materials are used properly, detection ranges are from 20 to 3,000 ppb Total BTEX for water and from 0.2 to 30 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 equal parts of benzene, toluene, ethylbenzene, o-, m-, and p-xylene. The antibody also responds to other lower aromatic hydrocarbons, including naphthalene, and can be used for the semiquantitative indication of petroleum fuels depending on their content in these aromatic hydrocarbons. It can be recalibrated in terms of these fuels with the option of developing appropriate conversion factors relative to the BTEX calibration. Quantitations in this assay are based on three-point calibrations with standard materials (which are provided). With the use of a field or laboratory photometer, the assay provides an estimate for the concentration of analytes in the sample by comparison with the color produced by a testing standard. The system allows the user to select a target concentration appropriate for a particular project. Sample extracts are diluted to the most sensitive region of the standard curve for a particular BTEX concentration.
Due to the high volatility 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. The RaPID assay can tolerate up to 1,000 ppm of some inorganic ions and metals. Conditions for sample handling are important.
Additional findings are described in an Evaluation Report which is available from DTSC.
A copy of the published Certification Notice may be obtained by contacting us at:
File last updated: October 9, 1996