Table 9. Comparison between on-site GC-TID and
CRREL laboratory (Method 8330) results for TNT and
2,4-DNT in solvent extracts of ETV soil samples.
Analyte concentration (mg/kg)
2,4-DNT
TNT
TID
HPLC
TID
HPLC
1.
14
16
80
85
2.
8.8
9.4
84
81
3.
8.5
10
82
82
4.
7.2
9.8
73
84
5.
0.7
0.69
7.7
6.5
6.
0.6
0.65
7.3
6.4
7.
0.7
0.80
7.1
7.0
8.
0.6
0.73
6.8
6.7
9.
0.7
0.72
9.9
8.6
10.
0.7
0.72
8.0
6.9
11.
0.6
0.62
7.7
6.4
12.
0.6
0.74
7.7
7.7
Median and range of the % differences for analysis pairs (HPLC
reference value).
2,4-DNT
TNT
Median
10.1
2.6
Range
26.5 to 1.45
13.1 to 20.3
extracts were reanalyzed back at CRREL by both GC-
performed on the same sample extracts that had been
TID and GC-ECD (Table 10). The GC-TID analysis
prepared and analyzed on site by GC-TID. Table 9 also
was performed a second time, just prior to GC-ECD
includes the TNT values obtained, to indicate that
analysis, because this analyte is known to be unstable.*
analyte concentrations had remained stable during stor-
Even though this is a limited data set (n = 8), a median
age. A review of the results in this table shows that
%D value of less than 26% indicates that there was rea-
CRREL-HPLC results were consistent with the on-site
sonable agreement between the two methods of analy-
GC-TID results for both TNT and 2,4-DNT. The poor
sis for tetryl. The reference laboratory failed to report
agreement found for 2,4-DNT between the on-site GC-
tetryl values above 0.5 mg/kg for these same samples.
TID and reference laboratory perhaps was an artifact
of the low number (n = 12) of data points and small
Prior to participation in the ETV verification test,
six pre-demonstration samples were distributed for
range of concentration (0.5 to 50 mg/kg). Close inspec-
analysis. These soils, which had been extensively ana-
tion of the results for 2,4-DNT shows two apparent
lyzed by ORNL using Method 8330, were analyzed at
trends: 1) as was true for the other two explosives, the
CRREL by GC-TID. Table 11 shows the HMX results
GC-TID values for the sample quadruplicates were
obtained for five of these samples (the sixth sample
more precise than the reference laboratory (one of the
contained no HMX). The GC-TID results for HMX in
reference laboratory quadruplicate sets had the highest
this table were very promising. However, during the
%RSD [122%] for this comparison study); 2) the refer-
ETV program, values for HMX were not reported be-
ence laboratory concentration estimates were higher
cause of the inability to consistently establish a response
than for the GC-TID. However, the only way to resolve
for this analyte that systematically increased over the
which set(s) of analyses is more likely to be correct
chosen calibration range. Failure to consistently achieve
would have been to include some soil samples spiked
with 2,4-DNT so that an assessment of accuracy could
be performed.
Values for tetryl in these soil samples were obtained
*Personal communication, Marianne E. Walsh, Chemical
during the ETV verification test, and the same sample
Engineer, CRREL, Hanover, New Hampshire, October 2000.
14
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