design allowed us to examine batch-to-batch preci-
To prepare a vapor-fortified soil for analysis,
sion, since duplicate samples were prepared in dif-
20.0 mL of MeOH was added to one of the sup-
ferent desiccators. The design also permited evalu-
plied VOA vials. Then an ampoule with its sealed
ation of intra- and interlaboratory analytical preci-
tip pointing toward the bottom and representing
sion.
one of the three soil subsample pairs, 1 or 2, which
The sample packages distributed to each partici-
were to be distinguished throughout, was placed
pating laboratory contained:
into the VOA vial. Once the VOA vial was capped,
Eight VOA vials (one extra);
the ampoule was broken by hand shaking, to
Seven sealed glass ampoules containing soil
allow the soil to become dispersed. A practice soil
[three pairs (1 & 2) of vapor-fortified soils
subsample (D) was included to allow the analyst a
labeled A, B and C, and one blank soil
chance to determine how hard to shake a VOA
labeled D for practicing the ampoule-breaking
vial when breaking an ampoule filled with soil.
operation];
We recommended that the analyst wear rubber
One QA ampoule (VOA-2, Ultra Scientific)
gloves and that the strength of shaking be in-
with certified concentrations of Ben, Tol and
creased slowly and not increased further once the
TCE* in MeOH; and
ampoule was broken. Our experience has shown
Handling and analysis instructions and
that only a portion of the sealed tip has to be bro-
reporting forms.
ken for the soil to be released. However, if, after
two minutes of hand shaking, soil remained
trapped in the ampoule, shaking was to be contin-
Soil subsample and QA sample handling
ued until complete dispersion resulted. The meth-
and analysis
It was imperative that the procedures used by
anolic extracts were transferred after the soil had
settled (approximately 20 minutes) by opening the
each laboratory be as consistent as possible to mini-
VOA vial and withdrawing the specified aliquot
mize systematic errors. For this reason, very specif-
with an appropriate syringe.
ic handling and analysis instructions were provid-
The ampoules marked A and B contained
ed. Prior to analysis the laboratories were request-
vapor-fortified TB sediment and RMA soil, respec-
ed to calibrate their instrument for the analysis of
tively. A 50.0-L aliquot of the 20.0-mL MeOH ex-
TDCE, TCE, Ben and Tol over a range of at least 1
traction solution was transferred with a 100-L
to 100 g/L. Analyses of both the QA standard and
the soil subsamples were to be performed within a
syringe to a 5.00-mL syringe containing 4.90 mL of
single day and within one month of sample receipt.
water. To keep a constant volume of MeOH add-
ed to the purge-and-trap vessel, 50.0 L of ana-
Between receipt and analysis the entire sample set
was to be refrigerated (4C). All analyses were per-
lyte-free MeOH was also added with a fresh sy-
formed by PT/GC/MS following the general
ringe.
guidelines of SW 846, Method 8240 for VOC con-
Ampoules marked C contained vapor-fortified
centrations greater than 1 g/g (U.S. Environmen-
PBA soil. A 10.0-L aliquot of the 20.0-mL MeOH
extraction solution was transferred with a 25-L
tal Protection Agency 1986). The soil subsamples
were first dispersed in MeOH; then a portion of the
syringe to a 5.00-mL syringe containing 4.90 mL of
methanolic solution was combined with approxi-
water. To keep a constant volume of MeOH add-
ed to the purge-and-trap vessel, 90.0 L of ana-
mately 5 mL of water for PT/GC/MS analysis.
On the day of analysis, the analyst was request-
lyte-free MeOH was also added with a fresh sy-
ed to make a 1/20 dilution of the QA standard pro-
ringe.
vided, using the same MeOH that was to be used
for extracting the soil subsamples. A 100-L aliquot
Data packages
of the 1/20 dilution was added to 4.90 mL of water
Each laboratory was asked to provide the fol-
and then transferred to a purge chamber. This QA
lowing results:
standard was the first to be analyzed so that the
Instrumental calibration for TDCE, TCE, Ben
analyst could check the instrumental calibration. If
and Tol;
the results of this analysis were not within 20% of
Concentration estimates for TCE, Ben and
the certified concentrations for TCE, Ben and Tol,
Tol in the supplied QA standard, along with
they were supposed to reanalyze the QA standard
results for any other analytes detected,
and/or consider recalibration before continuing.
regardless of whether the instrument was
calibrated for them; and
Concentration estimates for TDCE, TCE, Ben,
*A commercial standard containing TDCE was not available.
3
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