Table 2. Response factors for the GC-NPD, based on the average
of triplicate measurements of both peak area and height.
A. Peak area response factors (SRI integrator peak area divided by mg/L
concentration).
Response factors ( 107)
Concentration
(mg/L)
2,4-DNT
TNT
RDX
4ADNT
2ADNT
10
6.13
5.29
23.3
8.72
11.0
5
6.21
5.18
23.6
8.74
11.1
1
5.32
4.61
21.3
8.28
10.5
0.5
4.57
4.46
19.8
8.35
10.1
0.25
5.13
3.85
17.4
9.34
11.1
B. Peak height response factors (SRI integrator peak height divided by mg/L
concentration).
Response factors ( 106)
Concentration
(mg/L)
2,4-DNT
TNT
RDX
4ADNT
2ADNT
10
5.67
5.51
24.5
9.45
10.1
5
6.04
5.35
25.1
9.67
10.3
1
5.60
4.77
22.7
9.08
9.55
0.5
5.18
4.43
20.0
8.70
8.69
0.25
4.94
3.82
18.0
9.03
9.19
to incorrectly prepared standards, the standards
Response factors
Tables 2 and 3 show the response factors ob-
were also analyzed by RP-HPLC. The response
tained for the five target analytes on the NP and
factors shown in Table 4 for RP-HPLC analysis
EC detectors, respectively, over the concentrations
failed to show any relationship to concentration,
shown in Table 1. The response factors for the ECD
and resulted in much lower relative standard de-
systematically decreased with increasing concen-
viations (RSDs). The superior precision of RP-
tration for all of the target analytes (Table 3) while
HPLC is due to a combination of variables: better
sensitivity, an automated 100-L sample injection
the opposite trend, to smaller extent, was observed
for the NPD for three of the five analytes (Table
volume, greater analyte peak symmetry, and bet-
2). To rule out the possibility that the slight increase
ter peak resolution. Figure 3 and 4 show the re-
in response factor seen for the NPD over this con-
sponses of these two detection systems to RDX.
centration range, which is unusual, was not due
Because the response of the ECD is more nonlin-
Table 3. Response factors (SRI integrator peak height divided
by mg/L concentration) for GC-EC detector, based on the aver-
age of duplicate meaurements.
Response factors ( 109)
Concentration
(mg/L)
2,4-DNT
TNT
RDX
4ADNT
2ADNT
1
1.14
1.13
0.748
0.789
0.832
0.5
1.93
1.83
1.05
1.07
1.14
0.25
2.82
2.48
1.27
1.31
1.39
0.1
4.37
3.84
1.56
1.42
1.46
0.05
5.31
4.78
1.70
1.35
1.41
0.025
6.17
5.08
1.75
1.49
1.39
0.01
7.29
5.64
1.86
ND*
ND
*Not measured by integrator.
7
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