Tests using munitions-fortified tap water, moni-
often present in the same samples. In addition to
toring well water, and sediment-deionized water
preserving these analytes successfully for at least
were used to demonstrate the effectiveness of this
seven days after collection, acceptable techniques
procedure. The procedure, however, does not ap-
must be simple and inexpensive to implement,
pear to be very practical on a large scale, particu-
must not introduce chemicals that increase the
larly for routine use in the field.
cost of disposal, and must be compatible with
Goerlitz and Franks (1989) tested chloroform
SW846 Method 8330 (EPA 1992). Specifically,
and mercuric chloride as preservatives and found
Method 8330 allows two analytical sequences de-
that addition of mercuric chloride at 60 mg/L was
pending on the detection limits required. If detec-
tion limits in the range of 1020 g/L are adequate,
successful in significantly reducing the rate of al-
teration of TNT in groundwater samples from
a direct injection, reversed-phase high-perfor-
Hawthorne AAP. They attribute the alterations to
mance liquid chromatographic (RP-HPLC)
aerobic microbiological transformation resulting
method is used. If lower detection limits are re-
in the generation of the 2- and 4-aminodinitro-
quired, water samples must first be preconcen-
toluene transformation products.
trated prior to analysis by RP-HPLC. The method
Maskarinec et al. (1986) investigated the use of
currently specified in Method 8330 is salting-out
solid-phase extraction, not only as a method of
solvent extraction with acetonitrile, but the use of
preconcentration of nitroorganics from water, but
either cartridge or membrane solid-phase extrac-
also as a means for storage/preservation prior to
tion (SPE) may be allowed as an alternative in the
analysis. In their study, three groundwaters were
future. It was our hope to develop a stabilization
fortified with a set of nitroaromatics, nitramines,
method appropriate for samples analyzed by any
and nitrate esters, extracted with Porapak R (a
of these procedures.
styrene-divinylbenzene copolymer with poly-
vinylpyrrolidone) and held for periods of up to 32
weeks prior to analysis. The authors report that
EVALUATION OF
the resin-adsorbed analytes were stable for at least
ALTERNATIVES
16 weeks. The analytical precision of the results
for TNT in particular was quite poor, however,
A number of potential options for preservation
and drawing firm conclusions from these data
were considered, including the use of mercuric
seems risky. Nevertheless, the use of solid-phase
chloride, sodium azide, chloroform, sodium thio-
extraction for this purpose was an innovative idea
sulfate, acetonitrile, acetonitrile with acidification
worthy of serious consideration, since precon-
to pH 3.5 using acetic acid, and acidification to pH
centration prior to determination is often neces-
2 using sodium bisulfate. The stabilization proce-
sary anyway to obtain the desired detection limits
dures that we decided to test were acidification to
for these analytes in water.
pH 2 using sodium bisulfate (Maskarinec et al.
Recently Maskarinec et al. (1990) reported on
1990) and the addition of acetonitrile combined
the use of acidification to pH 2 with sodium bisul-
with or without acidification to pH 3.5 with acetic
fate as a method of preservation for volatile or-
acid (Miller et al. 1983). The use of acidification
ganics in water. This method proved very effec-
with sodium bisulfate was selected because it
tive at extending the acceptable analytical hold-
would only require addition of a preweighed
ing times for aromatic hydrocarbons and ketones,
amount of a solid material to each water sample
both of which are subject to microbiological deg-
and could be easily implemented in the field. It
radation. Acidification with sodium bisulfate ap-
has also been tested for its effectiveness with other
pears to be a method that could be used conve-
analytes such as volatile organics in water and
niently in the field during sample collection.
was found to be effective at preventing biodegra-
dation of aromatic hydrocarbons (Maskarinec et
al. 1990). Acidification with sodium bisulfate
should not result in disposal difficulties for re-
OBJECTIVE
sidual samples since acidification is a common
The objective of the studies described here was
laboratory practice for sample pretreatment and
to evaluate several different approaches to preser-
is also often used for cleaning of containers and
vation with regard to their effectiveness in main-
other glassware. Water samples at pH 2 may cause
taining the integrity of nitroaromatics in water
some difficulties in either the direct method of
samples without inducing instability in nitramines,
analysis or the two alternative preconcentration
2
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