Determination of Nitroaromatic, Nitramine, and
Nitrate Ester Explosives in Water Using
SPE and GC-ECD
Comparison with HPLC
MARIANNE E. WALSH AND THOMAS A. RANNEY
INTRODUCTION
and HMX is reported to decompose prior to boil-
Nitroaromatic and nitramine explosives (Table
ing. In addition, the vapor pressure of HMX (1014
torr at 20C [Burrows et al. 1989]) is well below
1) are present in the groundwater at many military
installations in the United States (ATSDR 1997) and
what is typical for GC analytes. Nonetheless,
Europe (Levsen et al. 1993). Potential contamina-
explosives, including the nitramines, have been
tion of drinking water has led to extensive net-
determined by GC for many years, primarily for
works of groundwater monitoring wells. Water
forensic applications such as determination of
samples from wells in the United States are gener-
post-blast residues (Yinon and Zitrin 1993). GC
ally analyzed by U.S. Environmental Protection
methods for the determination of explosives in
Agency SW-846 Method 8330 (USEPA 1994, 1997).
water are summarized in Table 3. Environmental
This method involves extraction of water samples
analysis of explosives has been dominated by
using either salting-out or solid-phase extraction
HPLC protocols because, for the most part, quanti-
(SPE) and analysis of the acetonitrile extract using a
tative GC results have been limited to the nitroaro-
high-performance liquid chromatograph equipped
matics (Levsen et al. 1993).
with an ultraviolet detector (HPLC-UV) (Jenkins et
Hable et al. (1991) were the first to report quanti-
al. 1994). Certified reporting limits (Hubaux and
tative GC determination of HMX in water. The
Vos 1970) range from 0.03 to 0.3 g/L (Jenkins et al.
nitroaromatics (2,4-DNT, 2,6-DNT, and TNT) were
1994, Winslow et al. 1991), and are sufficiently low
extracted using toluene, and the more polar nitra-
for determining whether water quality criteria are
mines (HMX and RDX) were extracted from a sepa-
met for most of the analytes for which criteria have
rate subsample with glass-distilled iso-amyl acetate.
been determined (Table 2).
Successful GC analysis was obtained using deacti-
Because of the prevalence of gas chromato-
vated injection-port liners, high injection-port tem-
graphs (GC) in environmental labs, an alternative
peratures, and short, wide-bore capillary columns.
Another factor was the elimination of contact be-
another option for analysis. Some of the Method
tween the analytes and metal parts of the injector.
8330 analytes are already included as analytes in
Elution of intact HMX, not a thermal degradation
current gas chromatographic SW-846 methods
product, from the GC column was confirmed by
(USEPA 1997). These include the nitroaromatics
GC/MS. The certified reporting limits were similar
NB, 2,4-DNT, 2,6-DNT, 1,3-DNB, 1,3,5-TNB, and
to those obtained using Method 8330 (Jenkins et al.
the isomers of NT. The physical properties of some
1992) for RDX, TNT, and 2,4-DNT, significantly
of the other Method 8330 analytes, principally the
higher for HMX, and lower for 2,6-DNT (Table 2).
nitramines, would lead one to believe that GC
The goal of our work was to develop a GC
analysis would be impractical. High melting
method that includes all the Method 8330 analytes
points, low vapor pressures, and thermal lability
in a single extraction step, and that uses commer-
are characteristic of the nitramines. For example,
cially available and routinely used instrumenta-
the melting point of HMX is 275C (Meyer 1987),
tion. We also included other analytes that might be
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