Table 12. Concentration (g/L) estimates obtained for the most commonly found analytes by HPLC
SPE
Concentration
SPE
Concentration
Source
method
HPLC GC-ECD
Source
method
HPLC GC-ECD
TNT
HMX
KSS AAP
Cartridge
0.20
0.10
LAAP
Cartridge
0.3
0.5
LAAP
Cartridge
0.4
0.1
Umatilla
Disk
0.29
0.60
LAAP
Cartridge
0.5
0.3
Umatilla
Disk
0.22
0.59
Umatilla
Cartridge
0.31
0.21
LAAP
Cartridge
2.4
1.2
LAAP
Cartridge
152
142
LAAP
Cartridge
19
13
Umatilla
Cartridge
241
233
CFB-Valcartier
Cartridge
26
26
CFB-Valcartier
Cartridge
97
110
LAAP
Cartridge
390
405
LAAP
Cartridge
2430
2876
LAAP
Cartridge
116
109
LAAP
Cartridge
2890
3721
Umatilla
Cartridge
141
179
LAAP
Cartridge
182
147
LAAP
Cartridge
7500
7781
LAAP
Cartridge
10500
12168
LAAP
Cartridge
216
217
CFB-Valcartier
Cartridge
219
280
CFB-Valcartier
Cartridge
250
308
TNB
LAAP
Cartridge
0.1
0.02
CFB-Valcartier
Cartridge
251
285
LAAP
Cartridge
1.0
0.4
LAAP
Cartridge
1300
1378
LAAP
Cartridge
1860
1842
LAAP
Cartridge
1.9
1.0
LAAP
Cartridge
15.6
33.8
LAAP
Cartridge
22.3
34.2
RDX
KSS AAP
Cartridge
0.2
0.2
LAAP
Cartridge
649
1128
LAAP
Cartridge
742
782
Umatilla
Disk
0.27
0.20
LAAP
Cartridge
9110
11991
KSS AAP
Cartridge
1.6
0.95
CFB-Valcartier
Cartridge
1.7
1.0
LAAP
Cartridge
9150
10640
CFB-Valcartier
Cartridge
2.0
0.56
LAAP
Cartridge
2.4
0.28
2,4-DNT*
<d
LAAP
Cartridge
3.6
0.6
LAAP
Cartridge
0.07
<d
Umatilla
Disk
4.9
4.9
LAAP
Cartridge
0.06
<d
LAAP
Cartridge
0.05
Umatilla
Disk
5.2
5.1
<d
Umatilla
Cartridge
6.5
5.2
LAAP
Cartridge
0.15
Umatilla
Cartridge
6.7
7.0
LAAP
Cartridge
0.69
0.36
LAAP
Cartridge
10.7
11.8
LAAP
Cartridge
8.9
1.2
CFB-Valcartier
Cartridge
29.8
37.7
LAAP
Cartridge
24.5
18.7
CFB-Valcartier
Cartridge
30.9
34.7
LAAP
Cartridge
46.8
33.6
LAAP
Cartridge
127
126
CFB-Valcartier
Cartridge
33.8
44.1
LAAP
Cartridge
845
590
LAAP
Cartridge
142
84.8
LAAP
Cartridge
1430
1973
LAAP
Cartridge
442
341
LAAP
Cartridge
2060
2241
LAAP
Cartridge
3710
3640
LAAP
Cartridge
11800
8175
LAAP
Cartridge
23400
20833
* In several extracts, 2,6-DNT was detected by GC-ECD, but not by HPLC.
<d = Less than detection limit.
Concentration estimates (Table 13, Table A1)
Spike recovery and method detection limits
To obtain an estimate of the accuracy of the GC
obtained by the three methods of calibration were
method, we spiked seven replicate 500-mL reagent-
similar for many of the analytes. Using average
grade water samples at the concentrations shown
in Table 13. The explosives were extracted from
resulted in estimates that were generally lower
the water using Empore SDB-RPS disks, which
than when using a quadratic model or linear in-
were eluted with 5.0 mL of acetonitrile, which re-
terpolation. The calibration factors for each of
sults in a preconcentration factor of 100. Found
these analytes, while still within the 20% RSD cri-
concentrations and recoveries were computed
teria for linearity, noticeably decline with increas-
using three methods of calibration: average cali-
ing concentration; estimates of concentrations in
bration factor, a nonlinear calibration curve, and lin-
real samples will therefore have variable degrees
ear interpolation from the calibration curve.
of error depending on the point within the cali-
15
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