Table 11. Recovery and repeatability of GC and HPLC determinations of analyte con-
centrations in spiked water samples.
Found conc. (g/L)
Spiked conc.
Avg recovery
RPD*
(g/L)
Membrane 1
Membrane 2
(%)
(%)
a. Empore SDB-RPS 47-mm diameter
GC-ECD
DNB
5.06
4.77
4.35
90
9.4
2,6-DNT
5.08
4.88
4.48
92
8.7
2,4-DNT
5.12
4.78
4.50
91
6.1
TNB
5.04
4.33
4.25
85
1.7
TNT
5.01
4.72
4.63
93
1.9
RDX
10.0
9.55
9.32
94
2.4
4-Am-2,6-DNT
5.06
4.51
4.28
87
5.1
2-Am-4,6-DNT
5.02
5.74
5.22
109
9.5
HMX
50.1
49.7
47.0
96
5.6
HPLC-UV
DNB
5.06
5.45
5.26
106
3.7
2,6-DNT and 2,4-DNT†
10.2
10.6
10.2
102
3.9
TNB
5.04
5.62
5.18
107
8.1
TNT
5.01
6.04
5.48
115
9.8
RDX
10.0
10.3
10.3
103
0.2
4-Am-2,6-DNT and 2-Am-4,6-DNT†
10.1
10.8
10.3
105
5.2
HMX
50.1
45.9
46.9
93
2.2
Found conc. (g/L)
Spiked conc.
Avg recovery
RPD*
(g/L)
Cartridge 1
Cartridge 2
(%)
(%)
b. Waters Sep-Pak Vac Porapak RDX cartridges
GC-ECD
DNB
5.06
5.20
4.66
98
11.1
2,6-DNT
5.08
5.29
4.87
100
8.3
2,4-DNT
5.12
5.03
4.80
96
4.6
TNB
5.04
4.92
4.73
96
3.8
TNT
5.01
5.26
5.07
103
3.7
RDX
10.0
10.8
10.6
106
1.8
4-Am-2,6-DNT
5.06
5.05
4.58
95
9.6
2-Am-4,6-DNT
5.02
5.26
4.85
101
8.1
HMX
50.1
68.8
67.7
136
1.6
HPLC-UV
DNB
5.06
5.76
5.70
113
1.1
2,6-DNT and 2,4-DNT†
10.16
11.0
11.0
108
0.3
TNB
5.04
5.71
5.67
113
0.7
TNT
5.01
5.97
5.99
119
0.4
RDX
10.0
12.5
12.1
123
3.3
4-Am-2,6-DNT and 2-Am-4,6-DNT†
10.1
10.6
10.6
105
0.4
HMX
50.1
55.5
56.2
111
1.3
* Relative percent difference.
† Peaks not resolved.
wide range of concentrations. Discrepancies be-
CRREL. All GC-ECD analysis was done at CRREL.
tween the two methods of analysis, however, do
Gas chromatograms were obtained on the DB1
exist. The GC appeared to underestimate the con-
analytical column, and RTX-200 and RTX-225 con-
centration of RDX in some of the low concen-
firmation column (Fig. 7).
tration samples. However, the ECD is a more
All comparisons of HPLC and GC-ECD deter-
selective detector, so this apparent underestima-
minations were done on extract splits. Concentra-
tion may not be real due to an interference with
tion estimates obtained by the two methods of
HPLC. Secondly, tetryl was detected by GC in
determination for the most commonly found ana-
some LAAP extracts, but not by HPLC. We sus-
lytes (HMX, RDX, TNT, TNB, and 2,4-DNT) (Table
pect that when we analyze a tetryl standard by
12) compared favorably for most samples over a
13
Previous Page
