from the U.S. Army Environmental Center, Aber-
tering them on a 47-mm vacuum filter apparatus
deen Proving Ground, Maryland. Individual stock
and adding several mL of acetonitrile to swell the
standards were prepared in HPLC-grade acetoni-
membrane before clamping the reservoir in place.
A 15-mL aliquot of ACN was then added and
trile (Baker). Combined working standards were
allowed to soak into the membrane for 3 min. The
in acetonitrile and were diluted 1:1 with Milli-Q
vacuum was then turned on and most (but not
Type I water (Millipore Corp.).
all) of the solvent was pulled through the mem-
brane. A 30-mL aliquot of reagent-grade water
RESULTS AND DISCUSSION
was then added and the vacuum resumed. Just
before the last of this water was pulled through
Determination of retention capacity of the
the membrane, the vacuum was removed, the res-
SDB-RPS membrane for HMX and RDX
ervoir filled with a 500-mL sample, and the vacu-
The retention of HMX and RDX by the SDB-RPS
um resumed. This sample extraction took from 5
membranes was tested by extracting a 2-L aliquot
minutes to an hour, depending on the amount of
of reagent-grade water that had been spiked with
100 g/L of HMX and RDX using aqueous stock
suspended matter present. Once the water was
eluted, air was drawn through the membrane for
standards. Samples of the water passing through
1 min to remove excess water. These extractions
the membrane were collected every 250 mL and
were conducted six at a time using an Empore
analyzed by RP-HPLC using the direct analysis
extraction manifold (3M Corporation). Vials (40
protocol. Results are plotted in Figure 1. No de-
mL) were placed below the outlets of the six mem-
tectable breakthrough occured for either analyte
100
HMX
80
RDX
60
40
20
0
400
800
1200
1600
2000
Volume of Effluent (mL)
Figure 1. Breakthrough curve for HMX and RDX with SDB-RPS membrane.
branes, a 5-mL aliquot of ACN was added to each
until more than 1 L of water had been extracted.
reservoir, the acetonitrile was allowed to soak into
Thus, it appears that the SDB-RPS membranes
have an increased retention capacity for the very
the membrane for 3 min, and then the vacuum
polar nitramines relative to that observed with the
was applied to pull the acetonitrile through the
initial SDB membranes used in an earlier study
membranes into the vials. Each resulting extract
(Jenkins et al. 1992, 1994).
was removed with a Pasteur pipette, the volume
was measured in a 10-mL graduated cylinder, and
it was diluted 1:1 with reagent-grade water be-
Cleanliness of Porapak RDX cartridges
fore analysis.
and SDB-RPS membranes
Aqueous solutions of individual analytes were
prepared by placing several hundred milligrams
Preparation of analytical standards
of each SARM into brown glass bottles and stir-
All standards were prepared from standard
analytical reference materials (SARMs) obtained
ring for 2 days at room temperature. Each solu-
4
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