Table 5. On-site analytical methods for explosives in soil, percent interference* or cross-reactivity†.
Nitroaromatics
Nitramines
Other
Test
method
TNT
TNB
DNB 2,4-DNT
2,6-DNT 2-AmDNT 4-AmDNT
Tetryl
RDX
HMX
PETN
TNT
CRREL
100
100
100
100
100
NC
NC
100
NC
NC
EnSys RISc
100
100
100
100
100
NC
NC
100
NC
NC
USACE
100
NC
NC
DTECH
100
23
4
11
<1
35
<1
<1
Idetek Quantix
100
47
1
2
0.5
2
6.5
<1
<1
EnviroGard:
Plate
100
7
2
41
<1
41
<1
<1
<1
Tube
100
3
2
20
1
17
0.3
Ohmicron RaPlD
100
65
2
4
<1
3
1
5
<1
<1
Assay
ENVIROL
100
CL
CL
Pos
Pos
NC
NC
Neg
NC
NC
NC
RDX
CRREL
NC
NC
NC
NC
NC
NC
NC
NC
100
100
100
EnSys RISc
NC
NC
NC
NC
NC
NC
NC
NC
100
100
100
DTECH
<1
<1
<1
<1
<1
<1
<1
<1
100
3
<1
HMX
CRREL
NC
NC
NC
NC
NC
NC
NC
NC
100
100
100
EnSys RISc
NC
NC
NC
NC
NC
NC
NC
NC
100
100
100
*Interference for colorimetric methods.
†Cross-reactivity for immunoassay methods at 50% response (IC ).
50
Blank cell = no data.
NC = No color development.
CL = Removed by cleanup steps.
Pos = Positive interference.
Neg = Negative interference.
analysis prior to colorimetric analysis, these inter-
TNT test kit, and 3% HMX cross-reactivity for the
ferences can be observed. Many of the immunoas-
RDX test kit. The following simple example illus-
say methods use a reverse coloration process, and
trates cross-reactivity, but in practice, it is not prac-
humic matrix interference results in less color
tical to calculate contaminant concentrations in this
development, hence on-site method results are
manner because of synergistic effects and because
biased high as compared to laboratory results. Ni-
cross-reactivity is nonlinear. Using the same
trate and nitrite, common plant nutrients in soil,
sample as the colorimetric example above, if a soil
are potential interferents with the CRREL and
sample (as analyzed by Method 8330) contains 100
EnSys RISc colorimetric procedures for RDX. An
ppm each of TNT, TNB, RDX, HMX, and tetryl,
extra processing step may be used to remove these
the TNT field immunoassay kit would measure
interferents in soils that are rich in organic matter
~158 ppm (100 TNT + 23 TNB + 35 tetryl), and the
or that may have been recently fertilized.
RDX field method would measure ~103 ppm (100
The performance of field explosives analytical
RDX + 3 HMX). If the same sample did not con-
methods on other solid-phase environmental treat-
tain tetryl, the TNT test kit would measure ~123
ment matrices such as incineration ash,
ppm (100 TNT + 23 TNB), and the RDX test kit
biotreatment residues such as compost or sludges
would still measure ~103 ppm.
from slurry phase bioreactors, cement-based so-
lidification or stabilization material, or granular
Matrix interferences
activated carbon from groundwater treatment sys-
Both colorimetric and immunoassay methods
tems, have not been extensively evaluated and will
may be subject to positive matrix interference from
most likely be subject to matrix interferences or
humic substances in soils, resulting in yellow ex-
low extraction efficiencies. The performance of
tracts. For colorimetric methods, interference may
field methods on these matrices should be evalu-
be significant for samples containing less than 10
ated against laboratory methods on a site-specific
ppm of the target analyte. Through careful visual
basis.
19
Previous Page
