ter are summarized by Crockett et al. (in press).
equate separation for the suite of analytes com-
Currently available on-site methods for explosives
monly encountered at explosives-contaminated
residues in water and soil generally can inexpen-
sites. Gas chromatography has not received wide
sively provide reliable estimates for the concen-
use for these analytes because of their thermal in-
trations of TNT and RDX. To our knowledge no
stability, but this analysis is possible by using a
on-site methods for explosives analytes other than
deactivated injection port and setting high linear
TNT or RDX have been reported except colorimet-
velocities for the carrier gas with short fused silica
ric-based methods for 2,4 DNT (Jenkins and Walsh
macrobore columns.
1992) and ammonium picrate (Thorne and Jenkins
It was the intent of this work to evaluate the
1995); the RDX colorimetric method has been used
potential for using a field-transportable gas chro-
to estimate octahydro-1,3,5,7-tetranitro-1,3,5,7-
matograph (GC) equipped with NP and EC de-
tetrazocine (HMX) concentrations at antitank fir-
tectors for on-site determination of individual ex-
ing ranges where the concentration of HMX was
plosives-related analytes. In particular an
several orders of magnitude higher than that of
emphasis was placed on the ability to determine
RDX (Jenkins et al. 1997, 1998). Therefore, no on-
(1) RDX in the presence of HMX for use at anti-
site methods currently provide comprehensive
tank firing ranges, (2) the biotransformation prod-
data for the suite of other manufacturing impuri-
ucts of TNT, which are 2ADNT and 4ADNT, and
ties and environmental transformation products
(3) simultaneous estimates for the suite of analytes
that are often present at explosives-contaminated
commonly encountered at explosive-contami-
sites (Walsh et al. 1993). In addition, for antitank
nated sites, since no currently available on-site
ranges, neither colorimetric nor immunoassay-
method can perform these three tasks.
based methods are capable of estimating concen-
trations of RDX when HMX is present at equal or
higher concentrations (Jenkins et al. 1998). Simi-
EXPERIMENTAL METHODS
larly, the concentration of TNT cannot be estimated
accurately using these methods when DNT, TNB
Calibration standards
or 2,4,6- trinitrophenylnitramine (tetryl) is present.
Analytical standards of 2,4-dinitrotoluene (2,4-
Moreover, no currently available on-site method
DNT), TNT, RDX, 4ADNT, 2ADNT, and HMX
provides for the determination of the major
were prepared from standard analytical reference
biotransformation products of TNT, 4-amino-2,6-
materials (SARMs) obtained from the U.S. Army
dinitrotoluene (4ADNT) and 2-amino-4,6-
Environmental Center, Aberdeen Proving Ground,
dinitrotoluene (2ADNT), which are sometimes
Maryland. A primary stock standard of approxi-
present at higher concentrations than TNT itself
mately 1000 mg/L for each analyte was prepared
(Jenkins et al. 1998). Thus there is a need for an
by transferring a weighed amount into acetone
on-site analytical method that can provide simul-
and diluting to 100 mL in a glass volumetric flask.
taneous estimates of the entire suite of analytes
Combined analyte secondary stock standards
that are commonly present at explosives-contami-
ranging from approximately 0.25 to 200 mg/L
nated sites.
were prepared by transferring up to 1.00 mL of
Gas chromatography has been used extensively
each primary stock standard with either glass sy-
for many years in on-site methods to identify and
ringes or glass pipettes into prepared bottles and
quantify specific target chemicals associated with
volumetric flasks containing acetone. Both the
fuels and solvents (U.S. EPA 1997). The availabil-
primary and secondary stock standards were
stored in a refrigerator at 4C and removed only
ity of the nitrogen-phosphorus detector (NPD) and
the electron capture detector (ECD) on field trans-
for brief periods while in use. Moreover, because
portable instruments provides selective detectors
of the instability of some of these compounds at
for nitrogen containing organic compounds and
low concentrations, working standards for the lev-
electron deficient compounds, respectively. Both
els shown in Table 1 were prepared daily (Walsh
detectors are selective and sensitive for the most
and Ranney 1998). Henceforth 2,4-DNT, TNT,
commonly encountered explosives such as TNT,
RDX, 4ADNT, and 2ADNT will be collectively
RDX and tetryl, as well as their manufacturing
called target analytes.
impurities and environmental transformation
products. Recently, Walsh and Ranney (1998) dem-
Instrumentation and separations
onstrated that gas chromatography with a fused
A field-transportable SRI model 8610 gas chro-
silica macrobore column (0.53 mm) provides ad-
matograph, equipped with a heated on-column
3
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