between the QA laboratory and CRREL for the
Table 6. Concentrations of benzene, toluene,
determination of BTEX concentrations (Table 6).
ethyl-benzene, and the xylenes (BTEX) in
Failure to yield a total BTEX value within
selected soil and water samples contaminated
the certified range of acceptance for a PE water
with GRO compounds.
sample (Table 6, WG-2, 0.10 mg BTEX/L vs.
Sample
Reference
certified range of acceptance 0.17 to 0.30 mg
no./ID
CRREL
QA lab
lab
BTEX/L).
High values for a sample duplicate, and a large
a. Soil (mg total BTEX/kg)
discrepancy among these values, while repeated
SG-1
48
36
33
SG-2
47
41
31
analysis at CRREL of an aliquot of extract from
SG-3
48
26
34
the same sample showed that the TPH was likely
SG-4
46
40
30
to be near or below the practical quantitation lim-
SG-8
3.2
2.6
2.1
its (Table 5a, SG-10 and SG-19, 180 and 690 mg
SG-11
1400
1400
740
TPH/kg).
SG-15
140
150
32
Failure to supply chromatograms with the data
SG-18
3.4
8.0
2.8
package that were legible or that were labeled with
b. Water* (mg total BTEX/L)
the test plan sample numbers.
WG-2**
0.22
0.23
0.10
WG-8
12.0
8.7
22.5
The combination of these concerns diminishes the cred-
WG-11
0.34
0.29
0.27
ibility of the reference laboratory data. The following
*The QA laboratory analyzed these water samples after
evaluation, therefore, only applies to those samples with
about 40 days of refrigerated storage, while the aliquots
target or with certified TPH concentrations, i.e., the
of the same samples were analyzed at CRREL after 9
matrix spikes and PE samples. One exception will be
days of refrigerated storage.
the use of values for the sample duplicates to evaluate
**Certified BTEX value 0.22 mg/L, performance accep-
tance range 0.170.30 mg/L.
precision.
Independent of using either the visual or the HM
2000 measurement method for estimating TPH concen-
trations, the values reported for the PE samples were
biased high, on average, by a factor of 3 relative to
the certified or the expected value (Table 8). In particu-
lar, the values reported for the PE water sample were
high (4 to 5 greater) compared to the certified value
of 1.0 mg TPH/L. For the matrix spike samples, both
on-site analysis methods were able, for a few samples,
to report average TPH values that fell within 25% of
Table 7. Percent dry weight of soil samples.
the expected concentration (Table 9). This level of
agreement between expected and estimated values was
Sample
% dry wt.
Sample
% dry wt.
attained by the visual method, for two out of eight ma-
SG-1, 2, 3, 4
100
SDM-8
93.5
trix spike duplicates analyzed, and by the HM 2000
SG-5, 6, 7
93.8
SDM-9
86.0
method, for one out of seven matrix spike duplicates
SG-8
86.3
SDM-10
72.7
analyzed. Unlike the PE samples, the values reported
SG-9
89.7
SDM-11
90.1
by these two methods of analysis for the matrix spike
SG-10
83.2
SDM-12
84.6
samples were both greater than and less than the ex-
SG-11
81.6
SDM-13
72.1
SG-12
84.7
SDM-14
87.4
pected concentrations.
SG-13
86.1
SDM-15
85.7
The percent relative standard deviations (%RSD)
SG-14
82.4
SDM-16
75.9
achieved by the HM 2000 for the sets of PE samples
SG-15
85.7
SDM-17
82.0
ranged from 35 to 56%, and were on the average greater
SG-16
87.3
SDM-18
74.5
than 40% (Table 8). At this level of precision (40%
SG-18
85.7
SDM-19
84.0
SG-19
83.7
M-2
86.5
RSD), the range of values established varied by at least
a factor of 2.5 from the lowest to the highest reported
SG-20, 21
86.0
M-3
85.7
M-4
79.4
TPH concentration. The relative percent differences
M-5
84.0
(%RPD) achieved by the HM 2000 for the matrix spike
M-6
80.3
duplicates and the sample duplicates were also used to
M-7
88.7
assess precision. The %RPDs ranged up to 140%
12
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