organic compounds (VOCs) (1,2-dichloroethylene
In a laboratory study, Devlin (1987) found that
and trichloroethylene [TCE]) were substantially
when a test solution containing a suite of ppb-level
lower in samples pumped through silicone rubber
VOCs was pumped through PE and Teflon (fluo-
tubing than those pumped through a type of fluo-
ropolymer) tubings, PE tubing was more sorptive.
ropolymer tubing. (Flow rates were ∼0.7 to 1.0 L/
Devlin also noted that after flushing the two sys-
min.)
tems with 2 L of the test solution, concentrations of
Several laboratory studies have also docu-
the analytes in samples taken from either type of
mented that sampling tubings can sorb organic
tubing were equivalent. However, Devlin noted
solutes. Curran and Tomson (1983) found that 50-
that a larger amount of test solution was required
ft lengths of PP, PE, and a fluoropolymer sorbed
to "equilibrate" the tubings for two of the analytes
very little naphthalene or p-dichlorobenzene
(tetrachloroethane [both tubings] and chloroben-
from low-ppb-level aqueous solutions pumped
zene [PE tubing]).
The results from Devlin's field studies, how-
through them. In contrast, the FPVC tubing
ever, do not show a consistent trend. At one site,
(Tygon) sorbed ~50% of these analytes from solu-
concentrations of contaminants in the samples tak-
tions pumped through it.
en using the fluoropolymer tubing were virtually
Ho (1983) found that the recovery of nine halo-
identical to those taken with PE tubing, while at
genated VOCs (alkanes and alkenes) from an
other sites concentrations of contaminants were
aqueous test solution was always lower in sam-
~30 to 50% higher in samples collected using the
ples taken using medical-grade silicone rubber
PE tubing.
than in samples taken using PTFE tubing. (Flow
rates varied from 2.6 L/min to 4.0 L/min.)
In a static study, Barcelona et al. (1985) exposed
Sorption studies of polymeric products
five common tubings (PP, PE, FPVC, PTFE, and sili-
other than tubing
Miller (1982) compared sorption of low ppb lev-
cone rubber) to a solution containing ppb levels of
els of six volatile organics (bromoform, PCE, TCE,
chloroform and to an aqueous solution containing
trichlorofluoromethane, 1,1,1-trichloroethane, and
a mixture of four organics (chloroform, trichloro-
1,1,2-trichloroethane) by three polymeric materi-
ethane, TCE, and tetrachloroethylene [perchloro-
als: RPVC, LDPE, and PP. These products were
ethylene or PCE]), each at ppb levels. In both ex-
purchased directly from the plastics manufacturer.
periments, they found that PTFE was the least
RPVC was by far the least sorptive of these three
sorptive material and that the FPVC and silicone
materials and LDPE was the most sorptive poly-
rubber tubings were the most sorptive. For exam-
mer tested.
ple, these tubings sorbed 80% of the chloroform
Reynolds and Gillham (1985) compared sorp-
within one hour.
tion of ppb levels of five halogenated aliphatic
Barcelona et al. (1985) also tested the effect of
organic compounds (1,1,1-trichloroethane, 1,1,2,2-
additional organic carbon (low ppm levels of
tetrachloroethane, hexachloroethane, bromoform,
polyethylene glycol) on sorption. They found that
and PCE) by six polymeric materials. The poly-
additional organic carbon affected sorption differ-
mers they tested included RPVC rod and a polya-
ently depending on the polymer. For example, sig-
mide (nylon) plate, and four types of tubing: PTFE,
nificant decreases in the sorption of chloroform
LDPE, PP, and latex rubber. They found that LDPE
were observed for PP and PE, but sorption was
and latex rubber were the most sorptive polymers
greater for FPVC and silicone rubber.
tested. A 10% loss of all five analytes was seen
Barcelona et al. (1985) noted that sorption by
within the first five minutes for samples exposed
the FPVC and PP tubings was at least two orders
to rubber and for four of the analytes exposed to
of magnitude greater than Miller (1982) had ob-
served for RPVC and PP materials. They felt that
the LDPE. RPVC and PTFE were the least sorptive
materials; it generally took days to weeks to see a
the higher density and greater crystallinity of
10% loss with these materials.
PTFE, PP, and PE may explain why these materi-
For all these polymers, Reynolds and Gillham
als were generally more inert in their study. They
(1985) attributed losses to absorption within the
concluded that sorption of chlorinated organic
polymer matrix. They were able to successfully
solvents from aqueous solutions by flexible tubing
model loss as a function of the partition coefficient
materials occurs by absorption into the polymer
of the organic compound between the aqueous
matrix. They concluded that flexible materials,
solution and the polymer (K), the diffusion coeffi-
such as silicone rubber and FPVC tubing, repre-
cient in the polymer (D), time, and surface area.
sent a virtual sink for chlorinated solvent sorbates.
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