Analysis of leachates

Table 2. Method detection limits (MDL) for analytes used in the tubing

material study.

MDL

Analyte

(mg/L)

Analyte

(mg/L)

nitrobenzene (NB)

0.0017

chlorobenzene (CLB)

0.0017

trans-1,2-dichloroethylene (TDCE)

0.0019

o-dichlorobenzene (ODCB)

0.0056

m-nitrotoluene (MNT)

0.0022

p-dichlorobenzene (PDCB)

0.0086

trichloroethylene (TCE)

0.0032

tetrachloroethylene (PCE)

0.0035

pound to methanol contained in a 50-mL glass

to account for any losses due to volatiles leaking

volumetric flask on a balance so that the concen-

through loose caps or sorption by the glass vials,

tration was approximately 2000 mg/L. A com-

Teflon liners, or plastic caps. There were two con-

bined standard (∼200 mg/L for each analyte) was

trols for each size vial and sampling time. All sam-

made by pipeting 10 mL of each single compound

ples were kept in the dark at room temperature.

standard into a 100-mL glass volumetric flask par-

When it was time to take a sample, an aliquot of

tially filled with methanol and then bringing to

each sample was transfered from each of the test

volume with methanol. These standards were

vials to an autosampler vial using a Pasteur pipet.

kept in a freezer. Working standards (∼10 mg/L)

Analysis was performed as described previously.

were made by pipeting 5 mL of the combined

standard (warmed to room temperature) into a

Analysis of leachates

50-mL glass volumetric flask partially filled with

Several of the chromatograms for solutions

deionized water, then bringing to volume with

exposed to the various tubings contained spurious

deionized water. This working standard was seri-

peaks. Thus, leaching of some type of constituents

ally diluted in deionized water, giving standards

occurred in samples exposed to nine types of tub-

of approximately 1.00, 0.100, and 0.0100 mg/L for

ing. In order to determine what some of these con-

each analyte. These working standard solutions

taminants were, we analyzed one of each of the

were made fresh each sampling period and run in

final (72 hr) samples for each of the twenty tubings

triplicate. The method detection limits (MDL) for

for semivolatile organics using GC-MS. Two GC-

the analytes (Table 2) were obtained according to

MS systems were used, each with a different col-

the EPA protocol described elsewhere (Federal

umn. The first system consisted of a Hewlett Pack-

ard (HP) 5890 series II gas chromatograph and an

HP 5970 mass selective detector with an HP1 cap-

illary column, 25-m 0.2-mm ID (0.33 m). The

Second sorption study

Because three of the tubings used in this study

second GC-MS system consisted of an HP 5890

(PTFE, ETFE, and polyamide) had different sur-

series II gas chromatograph, an HP 5972 mass

face-area-to-solution-volume ratios than the other

selective detector, and an HP 7673 auto-injector

with an HP5 capillary column, 30-m 0.25-mm

tubings, this study was conducted so that we

ID (0.25 m). Operating parameters were the same

could compare sorption of organic solutes by

these tubings with the other seventeen tubings.

on both instruments: initial column temperature of

60C (hold 1 min.), then ramp to 300C at 6C/

In this study, 5-cm pieces of the three tubing

types were placed in three different-sized glass vi-

min. (hold 19 min.). The injector/detector temper-

atures were 250C and 300C, respectively. Carrier

als (9, 25, and 40 mL). The test solution was made

of the same organic compounds and in the same

gas was helium with a linear velocity of 20 cm/s

set at 60C. For the first instrument, 3 L were in-

manner as in the previous study. The solution was

poured into the vials so there was no headspace,

jected manually, while for the second instrument, 1

L was injected by auto injection. Both injections

and the vials were capped with Teflon-lined plas-

tic caps. The total surface-area-to-solution-volume

had a splitless hold time of 45 sec. Mass scan was

ratios for PTFE were 0.70, 1.15, 3.55; for ETFE, 0.45,

from 45 to 550.

0.74, and 2.15; and for nylon, 0.69, 1.14, and 3.59.

Samples were taken after one hour, eight hours,

RESULTS AND DISCUSSION

and 24 hours. There were duplicates for each sam-

ple time and tubing type. The same-sized vials (9,

Sorption studies

25, and 40 mL) filled with test solution (without

For the first study, the data for all the replicates

tubing) served as controls. The controls were used

for each analyte, tubing, and time can be found in