whether 1) keeping LDPE tubing submerged dur-
trations ranged from 1.88 to 2.29 mg/L for MNT,
ing the wash procedure was required to remove
from 1.68 to 2.68 mg/L for TCE, from 1.33 to 3.25
contamination and 2) an additional decontamina-
mg/L for PDCB, and from 1.44 to 3.04 mg/L for
tion treatment following the wash procedure
PCE.
would remove the contaminants. Additional
treatments consisted of briefly rinsing with either
First VOC study--Effect of no treatment
methanol or hexane, or oven drying (Table 3). In
Even though sorption of the four analytes
this study, the pesticide solution was stirred for
(MNT, TCE, PDCB, PCE) by the test materials
two weeks, rather than the one week used in the
after 10 minutes' exposure was minimal (2% or
previous experiments.
less), contaminants were desorbed from these ma-
terials into the organic-free DI water (Table 5).
This indicates that carryover of these contami-
RESULTS AND DISCUSSION
nants is a problem, even though the contact time is
brief. Mean desorbed concentrations ranged from
VOC studies
7 to 27 g/L. This low level of contamination may
Tables A1A6 present the raw data from these
studies. In these studies, the mean initial concen-
be attributable to droplets of the test solution that
clung to the surfaces of the test pieces
Table 5. Summary of findings from the first VOC study--
when they were placed in the organic-
Effect of no treatment.
free water.
Following 24 hours' exposure, sub-
10-min sorption
24-hr sorption
stantial losses due to sorption were
Material MNT TCE PDCB PCE
MNT TCE PDCB PCE
observed, especially in the test solu-
a. Mean percent loss of analyte from test solution due to sorption
tions exposed to the PTFE test pieces
PVC
0.9
0.4
0.4
0.0
0.9
0.8
3.5
1.0
(Table 5). Desorbed concentrations
PTFE
0.4
1.9
2.1
1.9
0.9 13.7
22.2 31.7
were also considerably higher for
SS
0.9
0.0
0.0
0.0
0.5
5.5
4.8
7.4
PTFE and ranged from 16 g/L for
MNT to 205 g/L for PCE. In con-
b. Mean desorbed conc. (mg/L)
10-min sorb/10-min desorb
24-hr sorb/24-hr desorb
trast, sorption of analytes by the SS
Material MNT TCE PDCB PCE
MNT TCE PDCB PCE
and PVC test pieces was much less.
However, desorbed concentrations
PVC
0.015 0.016 0.022 0.027
0.015 0.028 0.058 0.032
for the SS materials were very similar
PTFE
0.007 0.018 0.023 0.018
0.016 0.151 0.178 0.205
SS
0.012 0.020 0.020 0.016
0.011 0.011 0.017 0.014
whether the sorption/desorption
MDL
0.004 0.006 0.008 0.008
protocol was 10 minutes/10 minutes
or 24 hours/24 hours. Desorbed con-
of rinsing.
samples exposed to the PVC test
pieces for 24 hours. This would indi-
Mean desorbed concentration (mg/L) after the following treatments
cate that most of the contaminants
No treatment
Rinsed samples
have remained at the surface of the
10-min sorb /10-min desorb
10-min sorb /10-min desorb
Material MNT TCE
PDCB PCE
MNT
TCE
PDCB
PCE
SS pieces and the PVC pieces ex-
posed to the test solution for 10 min-
PVC
0.007 0.009
0.015
0.011
LD <0.003
LD
<0.007
utes (i.e., little absorption occurred).
PTFE
0.002 0.012
0.017
0.020
LD
0.009
0.012
0.015
SS
0.006 0.006
0.010
0.007
LD
LD
LD
<0.005
If this is the case, then it may be pos-
sible to remove most or all of the con-
24-hr sorb/10-min desorb
24-hr sorb/10-min desorb
tamination from these surfaces by
PVC
0.006 0.009
0.014
0.012
LD
0.005
LD
<0.006
either rinsing or washing the surface.
PTFE
0.003
0.022
0.025
0.039
0.002 0.017
0.024
0.038
SS
0.008
0.007
0.020
0.019
LD <0.003
LD
<0.005
Second VOC study--Effect of
rinsing
24-hr sorb/24-hr desorb
24-hr sorb/24-hr desorb
Table 6 shows the effect of rinsing
PVC
0.011
0.031
0.045
0.037
0.006
0.026
0.036
0.044
on removal. Rinsing removed almost
PTFE
0.016
0.167
0.184
0.314
0.013
0.158
0.174
0.308
all of the contamination from the
SS
0.012
0.010
0.027
0.027
LD
LD
LD
<0.005
MDL
0.001
0.002
0.009
0.004
stainless steel surfaces. Rinsing also
removed nearly all the contamina-
LD = less than detection limit.
9
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