Method for Producing Performance Evaluation Soil/ Sediment Samples
for White Phosphorus Analysis
MARIANNE E. WALSH
tions in surface soils/sediments greater than 1,000
INTRODUCTION
g/g at discrete locations. Between areas of very
Site investigations for munitions residues at
high concentrations are much larger areas of very
low concentrations (0.001 to 0.01 g/g), which are
U.S. Army training areas may include analyses for
white phosphorus, which is used by the Army as
likely produced from deposition of colloidal par-
a smoke producing munition. Although white
ticles from the cloud and, with time, diffusion from
phosphorus (WP or P4) is pyrophoric, residues
or attenuation of solid chunks of white phospho-
may persist in wet environments (Walsh et al.
rus. To mimic the mechanisms by which real
1995).
samples were contaminated and to be representa-
Many laboratories that do not routinely analyze
tive of the wide range of concentrations typically
for white phosphorus are now being requested to
found (Table 1), two types of performance evalu-
do so. Unlike other analytes where standard or
ation samples were prepared: one at a high con-
certified reference materials are available for the
centration containing particulate white phospho-
preparation of calibration standards and spike
rus and one at a low concentration containing dis-
solutions, laboratories must prepare standard so-
solved white phosphorus.
lutions from commercially available material.
Likewise, performance evaluation samples are not
available. Therefore laboratories have no way of
METHODS
evaluating their overall analytical recovery.
The objective of this task was to develop and
Preparation of high concentration samples
demonstrate a method for producing performance
Production of white phosphorus particles
Particles of WP were produced from molten
evaluation soil/sediment samples for white phos-
phorus analysis. These samples may be used as
white phosphorus. Details of the procedure are
part of a quality assurance program for evaluat-
given in Appendix A; a brief description of the
ing the proficiency of a laboratory, verifying an
procedure follows. White phosphorus was ob-
analytical method, comparing analytical methods,
tained as sticks (16.1-mm diameter) stored in wa-
or training of new analysts.
ter from Aldrich Chemical Co. One stick of WP
was placed in an 18.3-cm-diam. glass dish under
3 cm of reagent water (MilliQ, Millipore Corpora-
tion) and a razor blade was used to obtain a 2-mm
APPROACH
slice. The edges of each slice were cut away so that
We sought to develop performance evaluation
only white phosphorus from the interior of the
samples that are representative of real samples.
stick was used. The mass of slice was approxi-
White phosphorus concentrations vary widely in
mately 700 mg. The piece of WP was transferred
under water to a test tube (13 100 mm) and the
soil/sediments that were contaminated by deto-
nations of WP munitions. Following the detona-
test tube placed in a 50-mL beaker, which was then
tion of a white phosphorus-containing projectile,
placed in a 1-L beaker containing reagent grade
white phosphorus burns, producing a dense white
water. The 50-mL beaker was used to support the
cloud containing phosphoric acid and trace
test tube containing WP. Additional test tubes were
amounts of WP and phosphine (Van Voris et al.
placed in the 1-L beaker. These test tubes served
1987). Solid chunks of white phosphorus may be
to isolate the particles of WP, once they were pro-
scattered by the detonation (Walsh and Collins
duced.
1993), producing white phosphorus concentra-
The water and white phosphorus were heated
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