additional 5 mL of unacidified acetone, we di-
Laboratory analysis for TNT
luted this solution with 5 mL of deionized water;
and other neutral nitroaromatics
a change from colorless or brownish- yellow to
and nitramines
deeper yellow revealed the presence of picrate.
Reversed phase HPLC analysis was conducted
The final absorbance at 400 nm was recorded. The
as described in EPA SW846 Method 8330 (EPA
corrected absorbance was converted to g/g of
1995a). Primary analysis was conducted on a
picric acid on the basis of the response from cali-
Supelco LC-18 column eluted with 1:1 methanol/
bration standards.
water at 1.5 mL/min. Absorbance was recorded
at 254 nm on a Spectra Physics Model 8490 vari-
able wavelength detector and peaks were recorded
Soil processing for
on a Hewlett Packard 3396 Digital Integrator op-
laboratory analysis
All soil samples were returned to the labora-
erated in the peak height mode. Selected samples
tory in coolers by overnight carrier. Upon receipt
were subjected to second column confirmation on
they were maintained at 4C until processed.
a Supelco LC-CN column using either 35:65
Samples were placed in plastic weigh boats, plant
methanol/water or 23:12:65 acetonitrile/metha-
and other debris were removed, and they were
nol/water, depending on the specific analytes de-
air dried in the dark until a constant weight was
tected in the primary analysis (Jenkins and Golden
achieved, usually within 48 hours or less. Weight
1993).
loss upon drying was used to calculate percent
moisture, which was then used to correct field-
Laboratory analysis
measured analyte concentrations to a dry weight
for ammonium picrate
Picrate was analyzed by RP-HPLC on a 25-
basis for comparison with laboratory results.
4.6-cm (5-m) LC-18 (Supelco) column. The pi-
Stones were removed from dried samples, which
were ground with a mortar and pestle to a fine
crate was eluted using 1.5 mL/min. of 60:40 0.05
powder. The weight of stones removed from each
M KH2PO4 (pH 3.5)/methanol and detected at
sample was recorded. Except for wheels 7 and 7R,
365 nm. Aliquots of the acetone extracts prepared
the amount of stones removed prior to laboratory
for the field method were diluted in eluent before
analysis did not significantly modify the soil from
analysis. A minimum dilution of 1 to 4, extract to
that analyzed in the field. For wheels 7 and 7R,
eluent, had to be used to obtain an acceptable
the amount removed was large and this had an
peak shape for picrate. The estimated detection
limit at this dilution was 0.1 g/g.
effect on the level of agreement of results from
on-site and laboratory analyses, as will be dis-
cussed later.
Chemicals and reagents
All standards for TNT and DNT were prepared
Duplicate 2.00-g subsamples from each discrete
from Standard Analytical Reference Materials
soil sample and seven replicate 2.00-g subsamples
(SARMS) obtained from the U.S. Army Environ-
from composites were weighed into 22-mL glass
mental Center, Aberdeen Proving Ground, Mary-
vials equipped with Teflon-lined caps. A 10.0-mL
land. Standards of TNT and DNT in acetone were
aliquot of acetonitrile was added to each vial, the
prepared using OmniSolv grade acetone from EM
contents were vortex mixed for 15 seconds, and
Science. Standards of ammonium picrate for field
the vials were placed in an ultrasonic bath that
was maintained below 35C with cooling water.
and laboratory procedures were prepared from
military grade material obtained from Hawthorne
Extractions were conducted for 18-hours. After
AAP.
extraction, the vials were cooled to room tem-
All acetone used in the field for soil extraction
perature and a 10.0-mL aliquot of aqueous CaCl2
(about 3 g/L) was added. The vials were vortex
and glassware cleaning was hardware grade ob-
mixed and allowed to stand for at least 15 min-
tained locally at each site. Acetonitrile and metha-
nol used in the laboratory for soil extraction and
utes while the solids settled. A portion of the
preparation of HPLC eluents were Baker, EM or
supernatant was removed using a Pasteur pipette
Mallinckrodt HPLC grade. Water used in the field
and filtered through a Millex SR membrane (0.5
m). The extracts were diluted, based on the re-
for cleaning, and for addition to extracts to en-
sure that an adequate water content was present
sults from on-site analysis, using 1:1 acetonitrile/
for the color-forming reaction, was distilled wa-
reagent grade water. Processed extracts were
maintained at 4C in the dark until analyzed.
ter obtained from local food stores. Laboratory
7
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