Evaluation of a Field Kit for Detection of TNT in Water and Solids
COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH
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Commercially available indicator tubes were evaluated for detection and measurement of TNT in water and soil. The tubes are intended for field use and can detect the presence of TNT in water and soil at concentrations as low as 40 microgramsliter and 0.5 microgramsgram respectively. Estimation of TNT concentration relies on measurement of stain length. Since the end point of the stain is diffuse, detecting the extent of stain length is very subjective. Therefore, it is imperative that standards and unknown samples be measured by the same analyst. Even when the same analyst makes all measurements, the accuracy and precision of concentration estimation is poor. Stain length was also found to depend on the sample matrix. Standards and samples must be matrix matched to enable proper calibration. Direct comparison of stain intensity, rather than length, to a standard at a criterion level successfully discriminated between standards with TNT concentrations above and below this level. The recommended soil extraction procedure using these indicator tubes was also evaluated. A 1-minute period of equilibration between soil and methanol resulted in incomplete TNT extraction. Percent recoveries were 58 to 70 of that achieved using a laboratory procedure involving an 18-hour equilibration period in a sonic bath. The percent extracted was directly related to the amount of TNT present in the soil.
- Test Facilities, Equipment and Methods
- Water Pollution and Control