Determination of Nitroaromatic,
Nitramine, and Nitrate Ester
Explosives in Soils Using GC-ECD
MARIANNE E. WALSH AND THOMAS A. RANNEY
extract is mixed 1:1 (v/v) with aqueous calcium
INTRODUCTION
chloride to flocculate fines prior to filtration and
The electron capture detector (ECD) has been
analysis by high-performance liquid chromatog-
used for many years to detect trace levels of ex-
raphy with an ultraviolet detector (HPLC-UV). Ex-
plosives. The selectivity and sensitivity of the ECD
plosives concentrations of 1 mg/kg (1 ppm) or
to the nitro group common to most explosives
higher may be determined using this procedure,
have made the ECD the most commonly used gas
and detection limits are sufficiently low for hu-
chromatographic detector for explosives residues
man health or ecological risk assessments. Jenkins
in environmental samples, especially in forensic
et al. chose HPLC-UV rather than GC for several
applications (Yinon and Zitrin 1993). Gas chro-
reasons: compatibility of the thermally labile
matographic analysis of solvent extracts of envi-
analytes with room temperature chromatographic
ronmental matrices can be problematic, especially
separation, large linear range of the detector, rug-
for the thermally labile nitramine and nitrate es-
gedness of the method, ability to analyze high con-
centration (>40 g/L) water samples by direct in-
ter explosives. Thus gas chromatography (GC) has
not been used routinely for quantitative analyses
jection, and compatibility of the solvent
of explosives residues in soil. Recently we devel-
(acetonitrile) used to extract soils with reversed-
oped an analytical method for explosives in drink-
phase HPLC.
ing water that was based on solid-phase extrac-
In the 1970s, Jenkins, Leggett, and Murrmann
tion (SPE) and determination by GC-ECD (Walsh
used GC-ECD when they characterized the vapors
and Ranney 1998). This paper describes the analy-
from military-grade TNT in conjunction with ef-
sis of soil extracts using gas chromatographic con-
forts to detect buried land mines by sampling the
ditions similar to those used to analyze water ex-
atmosphere (Murrmann et al. 1971, Jenkins et al.
tracts.
1974, and Leggett et al. 1977). Some solvent (ben-
Traditionally, determination of explosives in soil
zene) extracts of soil were analyzed as well. In-
served either forensic or hazardous waste investi-
strumentation at that time was not conducive to
gations. More recently, there is interest in
quantitative determination of explosives in soil,
ultrasensitive methods for determining explosives
especially on a routine basis.
in soil that could be used to detect buried land
Improvements in injection port liners, GC col-
mines (Rouhi 1997).
umns, and most recently the ECD detector (David
Jenkins et al. (1989) developed what is now the
et al. 1997) have led us to reexamine the utility of
standard method for explosives in soil (SW-846
the GC-ECD for determination of explosives in soil
Method 8330 [USEPA 1994]) to characterize mili-
for both hazardous waste site characterization and
tary sites contaminated with explosives residues
mine detection.
from the production or use of high explosives
Analytes of interest differ somewhat for haz-
munitions. For this standard analytical method, a
ardous waste characterization and mine detection
2-g soil sample is extracted by 18 hours of sonica-
(Table 1). Soil that was contaminated by the manu-
tion with 10 mL of acetonitrile (AcN). The AcN
facture or use of explosives most likely contains
Previous Page
