strumentation, even though lower levels of detec-
Table 9. Retention times for explosives using
tion could probably be achieved by GC-ECD. The
different oven temperature programs for NPD
GC-NPD, coupled with the sample preparation
and ECD.
methodologies described, offers the following fea-
tures:
NPD
ECD
retention time
retention time
Simultaneous determination of multiple tar-
Analyte
(min)
(min)
get analytes,
Adequate sensitivity,
NB
0.96
NA
A linear range of response (except at concen-
o-NT
ND
NA
trations less than 1 mg/L or 1 mg/kg) that
m-NT
ND
NA
p-NT
ND
NA
exceeds current field screening technologies,
1,3-DNB
2.4
NA
Faster analytical runs than the currently rec-
2,6-DNT
2.6
NA
ommended laboratory LC or GC methods,
2,4-DNT
3.0
0.97
Compatibility with hardware-store grade ac-
TNB
3.9
NA
etone.
TNT
4.1
1.7
RDX
4.7
2.7
One of the only limitations of this methodology is
4ADNT
5.3
4.2
that the instrumentation does require a fair
2ADNT
5.6
5.1
amount of support. In addition to a source of elec-
Tetryl
6.1
NA
trical power, the NPD requires independent
HMX
7.9
ND
NA Not analyzed.
Before recommending this methodology as an
ND Not detected at 10 mg/L concentration.
analytical approach for characterizing the extent
and type of explosive contamination in soil and
water, field trials need to be performed. Field veri-
para and meta nitrotoluenes, which are among the
fication would further establish the robustness of
least frequently encountered analytes found at
this analytical method and provide insight as to
sites contaminated with explosives. Therefore, this
the number of samples that could be processed
analytical method applies to most of the explo-
daily and better define the logistical requirements.
sives cited by SW846 Method 8830, the standard
Knowledge of all of these parameters is needed
laboratory method for explosives in water and soil.
before estimates of cost saving can be made. More-
An assessment of the upper range of the NPD's
over, as with other methods based on chromatog-
linearity was performed using the standards con-
raphy, unanticipated interferences may be encoun-
taining the five target analytes. This experiment
tered during field studies.
showed that the response of the NPD remains lin-
This on-site method offers the potential to es-
ear up to 100 to 200 mg/L. Therefore, the range of
linear response for these analytes is two to three
tablish timely concentrations for individual explo-
orders of magnitude.
sives well above and below current action levels.
Lastly, no impurities were detected by GC-NPD
Currently, this task cannot be unambiguously
achieved using current on-site methodologies,
analysis of hardware-store grade acetone. Further-
since they either lack adequate sensitivity and/or
more, the analysis of a 1-mg/L standard of the tar-
the selectivity required. Therefore, this field ana-
get analytes prepared in both hardware-store and
lytical method could fulfill a very useful function
reagent-grade acetone resulted in identical re-
in our effort to economically characterize active
sponses. This finding would eliminate the need
and formerly used manufacturing plants, ord-
to ship large quantities of acetone to the field.
nance works and disposal sites, depots, proving
grounds, impact ranges, firing points, etc.
SUMMARY
These preliminary findings indicate that a ro-
LITERATURE CITED
bust and rapid field GC-NPD analytical method
can be developed for the simultaneous identifica-
Bart, J.C., L.L. Judd, K.E. Hoffman, A.M. Wilkins,
and A.W. Kusterbeck (1997) Application of a por-
tion and quantification of explosive residues in
both soil and water matrices. When working with
table immunosensor to detect explosives TNT and
action levels for these analytes of 0.5 mg/kg and
RDX in groundwater samples. Environmental Sci-
2.0 g/L, for soil and water, respectively, a field-
ence Technology 31(5): 15051511.
transportable GC-NPD is a practical choice of in-
Crockett, A.B., H.D. Craig, T.F. Jenkins, and W.E.
12
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