Leaching study

Table 3. Summary of sorption study.

CONCLUSIONS - SR96_030016

SR96_03
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five to ten minutes. These losses reflect what

and the silicone-modified TPE tubings had four

might be sorbed by a virgin material. However,

spurious peaks, and chromatograms for the solu-

conditions in the tubing are dynamic and fresh

tions exposed to the PP, one of the plasticized

water would be continually replenished as it is

polypropylenes (formulation 1), the P(VDF-

pumped through the system. One might antici-

HFP), and the fluoroelastomer tubings each con-

pate that once equilibrium is reached, little or no

tained one spurious peak. The chromatograms

more losses of analytes would be expected, unless

for the solutions exposed to the rigid fluoropoly-

transfer to the atmosphere through the tubing was

mers, the polyethylenes, and one of the plasti-

significant. The question that then remains is how

cized polypropylenes (formulation 2) did not

much time is needed for the tubing to reach equi-

contain any spurious peaks. This plasticized PP

librium under dynamic conditions. Currently

tubing was the only flexible tubing that did not

there are no data available that answer this ques-

appear to leach any contaminants.

tion.

One test solution from each of the tubings that

was found to leach contaminants was analyzed

for semivolatile organics by GC-MS. We reported

Leaching study

When we compared the chromatograms of

only those matches where the quality of the

sample solutions exposed to the tubings with the

match was greater than 75%. Unfortunately, we

control sample solutions, we saw additional

were unable to identify most of the leachates us-

peaks in the solutions exposed to some of the tub-

ing this method. The sample solutions exposed to

ings. By the end of the experiment (72 hr), solu-

PP and the TPE tubings had one major peak,

tions exposed to nine of the tubings had extra or

which was tentatively identified as hexanedioic

spurious peaks, most likely indicating that some

dioctyl ester (90% match). This compound is

constituents had leached (Table 5). The chromato-

commonly used as a plasticizer and lubricant in

grams for the solutions exposed to the polyure-

the manufacture of polymeric materials. The

thane, polyamide, and PVC tubings contained at

polyamide tubing leached one primary contami-

least eight spurious peaks, with polyurethane

nant that we tentatively identified as n-butyl-

having the most (12). The chromatograms for the

benzene sulfonamide (90% match). The GC chro-

solutions exposed to the polyester-lined PVC shell

matogram for the sample solutions exposed to

Table 5. Number of spurious HPLC peaks found during tubing material study

and possible identification.

Contact time (hr)

Possible identification

( % match )

Flexible tubings

Plasticized PP (formulation 1)

not identified

Plasticized PP (formulation 2)

hexacosane (90%)

PVC

hexanedioic acid, dioctyl ester (83%)

TPE

P(VDF-HFP)

not identified

hexanoic acid, 2-ethyl (78%)

Polyurethane

Fluoroelastomer

not identified

Rigid tubings

LDPE

XLPE

PE in an EVA shell

PE cross-linked to EVA shell

not identified

Polyester lining in a PVC shell

hexanedioic acid, dioctyl ester (87%)

benzenesulfonamide, N-butyl (90%)

Polyamide

PTFE

PFA

ETFE

PVDF

FEP

FEP-lined PE

Boldface = Materials that leached several contaminants during the study.

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