pumping rate (100 mL/min) is used to sample a
Table 8. Total amount of
shallow well (< 50 ft), and 2) a faster flow rate is
TCE sorbed and desorbed
by tubing.
used (1 L/min) in deeper wells, although 24 hr
should be allowed for equilibration in the deep-
Sorbed1
Desorbed2
est wells (500 ft and greater). However, we real-
Tubing
(mg)
(mg)
ize that equilibration for 24 hr may not be prac-
PVDF
--
0.91
tical in all instances. We also recommend that
LDPE
--
28.7
there be additional testing with other analytes.
PP1
273
62.6
In this study, we were unable to detect (using
1
After pumping contamin-
an HPLC with a UV detector) that any organic
ated water through 100 ft of
constituents leached from any of the five tubings
tubing at 1 L/min for seven
tested when either a slow rate (100 mL/min) or a
days.
2
After pumping DI water
moderately fast rate (1 L/min) was used to
through tubing at 100 mL/
pump water through the tubings. These results
min for four days.
agree reasonably well with our previous static
Table 8 gives the amount desorbed by these
study (Parker and Ranney 1996), where, using
three tubings and also shows the amount sorbed
similar methods of analysis, we detected only
by the PP1 tubing. No estimate was made for
one constituent that leached from two of these
sorption by the other two tubings because losses
tubings [PP1, P(VDF-HFP)].
of TCE were not significant for them. After four
This study also shows that desorption of
days, it appears that only 23% of the TCE was re-
sorbed organic solutes, such as TCE, can be a
covered from the PP1 tubing.
problem if slow-flow pumping is used. This is
true whether the tubing is relatively nonsorptive
Leaching findings
(e.g., PVDF) or highly sorptive (e.g., PP1). Fur-
We did not observe any spurious peaks, using
thermore, pumping organic-free water through
RP-HPLC analyses with a UV detector, in the wa-
these tubings at this flow rate is not an effective
ter samples that were pumped through the
way to remove TCE.
PVDF, LDPE, or PP1 tubings at 100 mL/min. In
this case, the sensitivity of the analyses was
LITERATURE CITED
much greater because we were looking for low
g/L concentrations. However, our analysis time
Aller, L., T.W . Bennett, G. Hackett, R.J. Petty, J.H.
was not as long in this experiment as in our pre-
Lehr, H. Sedoris, D.M. Nielsen, and J.E. Denne
vious study (Parker and Ranney 1996) where
(1989) Handbook of Suggested Practices for the
leaching was observed. The results from this
Design and Installation of Ground Water Monitoring
study are consistent with the results from our
Wells. Dublin, Ohio: National Water Well Associ-
static study (Parker and Ranney 1996), where
ation.
only one constituent was detected leaching from
Backhus, D.A., J.N. Ryan, D.M. Groher, J.K.
any of the tubings, PP1.
MacFarlane, and P.M. Gschwend (1993) Sampling
colloids and colloid-associated contaminants in
ground water. Ground Water, 31(3): 466479.
CONCLUSIONS
Barcelona, M.J., J.A. Helfrich, E.E. Garske, and J.P.
The results from this study along with those
Gibb (1984) A laboratory evaluation of ground
from our previous study (Parker and Ranney
water sampling mechanisms. Ground Water
1996) show that, with respect to sorption, 1) gen-
Monitoring Review, 4(2): 3241.
erally rigid fluoropolymers should be used when
Barcelona, M.J., J.A. Helfrich, and E.E. Garske
sampling for organic contaminants using slow-
(1985) Sampling tubing effects on ground water
rate pumping (100 mL/min), especially if the
samples. Analytical Chemistry, 57: 460464.
contaminants are unknown, and 2) if a flexible
Boettner, E.A., G.L. Ball, Z. Hollingsworth, and R.
tubing is required, then P(VDF-HFP) or a fluo-
Aquino (1981) Organic and organotin com-
roelastomer are the least likely to bias test results.
pounds leached for PVC and CPVC pipe. U.S.
It appears that there are instances when a less
Environmental Protection Agency, Report Num-
expensive tubing such as LDPE can be used to
ber EPA600/181062.
sample less sorptive (more hydrophilic) analytes
Curran, C.M., and M.B. Tomson (1983) Leaching
such as TCE. These conditions are when 1) a slow
of trace organics into water from five common
14
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