On-Site Method for Measuring Nitroaromatic
and Nitramine Explosives in Soil and
Groundwater Using GC-NPD
Feasibility Study
ALAN D. HEWITT AND THOMAS F. JENKINS
analyzed resulting in a more spatially detailed
INTRODUCTION
characterization.
Until the last several years, almost all sites po-
The first on-site method for detecting explosives
tentially contaminated with toxic and hazardous
residues in water was reported by Heller et al.
wastes were characterized by shipping soil and
(1982) and later improved by Erickson et al. (1984),
water samples to off-site laboratories for analysis.
who extended its application to include soils. This
These off-site laboratories utilized powerful labo-
method was specifically aimed at the detection of
ratory instrumentation and followed methods
TNT and utilized a detection tube that had two
such as those that have been standardized through
sections. The first section contains a basic oxide
the U.S. Environmental Protection Agency's
that converts TNT to its Meisenheimer anion. This
SW846 Methods compendium. In general the data
colored species migrates to the second section of
obtained in this way were adequate to make deci-
the tube, where it is retained on a quaternary am-
sions on whether sites were contaminated at lev-
monium chloride ion exchange resin. Water
els that required remedial activities. Action levels
samples were pumped through this tube, and TNT
for explosives, although not universally accepted,
was detected visually by the development of a
have generally been based on water quality crite-
reddish stain on the second section of the tube.
ria. The interim EPA guidance indicates that con-
The concentration of TNT was estimated from the
centrations as low as 2 g/L for 2,4,6-trinitrotolu-
length of the stain produced. Soil samples are first
ene (TNT) may have some level of human toxicity
extracted with methanol, and then this solvent is
(U.S. EPA 1989). Action levels for soil have gener-
passed through the tube. The tubes have been
ally been in the milligram/kilogram range.
independently evaluated at CRREL and found to
A major downside of this approach is the time
provide reliable detection of the presence of TNT
at concentrations greater than 40 g/L, but the
involved in producing the data for making these
decisions. It often takes weeks to months after
ability to precisely and accurately quantify TNT
samples were collected before data become avail-
concentrations in water or soil was poor (Jenkins
able to project personnel. Secondly, this approach
and Schumacher 1990). Moreover, the 1-minute
was extremely expensive on a per sample basis,
extraction time specified for soil was insufficient
resulting in the analysis of a relatively few samples
for field samples.
to characterize large geographical areas. Recogni-
Stevanovic and Mitrovic (1990) developed a
tion of these problems led to the development of
method for TNT and 1,3,5-hexahydro-1,3,5-
analytical methods that could be used on site to
trinitrotriazine (RDX) that could be adapted for
provide adequate characterization when rapid de-
on-site analysis. In this method, water is passed
cisions were required. Because of lower analysis
through a porous disk coated with a thin film of
costs, these methods allowed more samples to be
silica gel, and TNT and RDX are adsorbed on the
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