Table 1. Extraction techniques used with on-site analysis methods.
Concentration
Extraction
range
TYPE
(g/g)
Method
Solvent
time
Soil/solvent
Colorimetric
EnSys
Acetone
3 min
10 g/50 mL
1 to 30
Erickson
Methanol
1 min
6 g/20 mL
0.3 to 30
Jenkins
Acetone
3 min
20 g/100 mL
1 to 22
Medary
Methanol
1 min
6 g/35 mL
4 to 90
Immunoassay
4.5g†/9 mL
EM Science (D TECH)
Acetone
3 min*
0.5 to 5.0
Idetek (Quantix)
Acetone
3 min
4.2g/21 mL
0.25 to 100
Millipore (EnviroGard)
Acetone
2 min
2 g/8 mL
1 to 100
Ohmicron
Methanol
1 min
10 g/20 mL
0.07 to 5
Ion mobility spectrometry
Barringer
Acetone-hexane
3 min
1 g/1 mL
Low ppb
*
Shaking several times over three-minute period.
†
Actual mass of soil will vary depending on soil density.
Objective
The main objective of our study was to determine the rate of extraction of secondary explosives
from highly contaminated soil to ensure that on-site methods currently available can provide suffi-
ciently accurate results for soils contaminated with percent levels of TNT and RDX. Field-contami-
nated soils from a number of installations were utilized in these assessments. Because the most
commonly used on-site methods for explosives in soil specify either acetone or methanol as the
extraction solvent, much of the work evaluated extraction using these solvents. Based on these
results, recommendations will be made on modifications to established protocols for available on-
site methods for determining whether concentrations exceed the 10% safety criterion. Since large
dilution factors (about 1 to 10,000) are required to reduce extract concentrations to the range suit-
able for these tests, a dilution procedure that is simple and sufficiently accurate and precise will be
provided.
Overview of on-site methods
Colorimetric TNT methods
The first on-site screening method for TNT in environmental matrices was reported by Heller et
al. (1982). This method was initially developed for water analysis and utilized a detection tube
containing two sections. The first section contained a basic oxide that converted TNT to its Meisen-
heimer anion (eq 1), which was retained by the anion exchanger in the second section of the tube.
Equation 1. MEISENHEIMER ANION
CH 3
CH 3
O2N
NO2
O2N
NO2
+
OH
OH
H
NO2
NO2
TNT
Since the Meisenheimer anion for TNT is highly colored, detection is achieved visually and quanti-
tation is made by measuring the length of the colored region of the tube. The use of these tubes for
detection of TNT in soil was reported by Erickson et al. (1984). Their method specifies extraction of
about 6 g of soil with 20 mL of methanol by manually shaking for one minute followed by filtering
2
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