Preservation of Water Samples Containing
Nitroaromatics and Nitramines
THOMAS F. JENKINS, PHILIP G. THORNE,
ERIKA F. MCCORMICK AND KAREN F. MYERS
1976). For TNB and TNT this results in a series of
INTRODUCTION
transformation products, with the most stable be-
There is an unavoidable delay between sample
ing 3,5-dinitroaniline (3,5-DNA) (from TNB) and
collection at hazardous waste sites and analysis at
the 2- and 4-amino-dinitrotoluenes (2ADNT and
off-site environmental testing laboratories.
4ADNT) (from TNT). Elsewhere, Goerlitz (1992)
Analytes must be sufficiently stable in the matrix
reported TNT losses as high as 75% after 20 days
under investigation using prescribed storage con-
of storage for unpreserved groundwater samples
ditions or they must be stabilized, usually by the
from Hawthorne Army Ammunition Plant. Miller
addition of chemical preservatives. Matrix-specific
et al. (1983) reported that 2,4-DNT, TNB, and sev-
analytical methods typically include a section de-
eral other nitroaromatics fortified into groundwa-
scribing storage conditions and acceptable hold-
ter from Sunflower Army Ammunition Plant dem-
onstrated significant instability when stored at 4C
ing times between sample collection and analysis.
The most commonly used analytical method in
in the dark without preservation. Given the dif-
the United States for nitroaromatics and nitramines
ferences in results for different waters, it appears
in water is SW846 Method 8330 (EPA 1992). The
that variations in physical, chemical, and micro-
preextraction holding time prescribed in this
biological properties of specific waters can pro-
method is seven days, with samples maintained
duce a wide range of effects, i.e., degradation
under refrigeration and no preservative specified.
mechanisms and rates are somewhat specific to a
However, two recent holding-time studies have
given water. Thus, preservation techniques appro-
indicated that the nitroaromatics frequently asso-
priate for nitroaromatics in water are needed and
ciated with munitions wastes can be subject to
should be used on a routine basis.
significant losses while being held prior to analy-
A protocol for preservation of 12 munitions-
sis. Maskarinec et al. (1991) found rapid loss of
related chemicals in water was developed by Miller
2,4-dinitrotoluene (2,4-DNT) in both surface wa-
et al. (1983) at the Midwest Research Institute.
ter and groundwater even when stored at 4C in
Several parameters were evaluated relative to their
the dark; they recommended a preextraction hold-
effect on analyte stability with time, including pH,
ing time of only four days for water samples to be
temperature, light, containers, and the presence
analyzed for 2,4-DNT. Grant et al. (1993) found
of sediment, salt, and acetonitrile (used as an anti-
very rapid losses of 1,3,5-trinitrobenzene (TNB)
bacterial agent). Several alternative preservation
and 2,4,6-trinitrotoluene (TNT) for surface water
techniques were tested using munitions-fortified
maintained at 2C in the dark, but loss of 2,4-DNT
water. The resulting data did not demonstrate large
was very small. Losses of 55% for TNB and 30%
differences among treatments, nevertheless, the
for TNT were observed after only seven days' stor-
following preservation technique was selected:
age, and the losses reached 77% for TNB and 45%
water samples are preserved by adding acetonitrile
for TNT after 14 days. The major loss mechanism
to the sample to achieve a 10% solution, the pH is
appears to be microbiological transformation re-
adjusted to 3.5 with glacial acetic acid, suspended
sulting in the reduction of one nitro group on the
particles are removed by centrifugation, and
samples are stored at 4C in amber glass bottles.
ring to amino (Won et al. 1974, McCormick et al.
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