Sampling Trace‐Level Organic Solutes with Polymeric Tubing Part 2. Dynamic Studies

Abstract

This is the second part of a study conducted to determine whether polymeric sampling tubing can affect organic analyte concentrations during a sampling event. In this part of the study, we looked for sorption and desorption of tricholoroethylene (TCE) and leaching of organic constituents in water pumped through five types of polymeric tubing. The materials tested were a rigid fluoropolymer, a flexible fluoropolymer, low‐density polyethylene (LDPE), and two plasticized polypropylene tubings. The effects of tubing length and flow rate were examined. The least sorptive tubings, both initially and at equilibrium, were the fluoropolymers. However, in some instances the LDPE tubing had little effect on TCE concentrations. This was when a slow flow rate was used to sample relatively shallow wells (50 feet [15 m] or less) or when a faster flow rate (1 L/min) was used to sample wells that are less than 500 feet (152 m). Further testing is recommended using more sorptive analytes. Using high performance liquid chromatography (HPLC), we were unable to detect any constituents leaching from any of the tubings used in these studies, even when a slow flow rate was used. However, desorption of sorbed analytes is a concern for all the tubings tested, including the rigid fluoropolymer.

MULTI INCREMENT® TCE vadose‐zone investigation

“…Parker and Ranney (1998) previously calculated an MDL of 0.0026 μg/mL for TCE using a larger ratio of methanol to water. Analysis of the second commercial standard resulted in a theoretical recovery of 103 percent.…”

Demonstration/Validation of the Snap Sampler Passive Ground Water Sampling Device

“…Previous studies by our laboratory (Parker and Ranney, 1998) have demonstrated that when lowflow purging and sampling is used, sorption by longer lengths of (non-equilibrated) polymer tubing can substantially reduce concentrations of some VOCs. In contrast, there are no losses of these analytes in samples collected with the Snap Sampler when it has been equilibrated before collection (Parker and Mulherin, 2007).…”

“…The findings were similar for the anions. There could be several reasons why VOC concentrations would be lower in the low-flow samples, including (1) the Grundfos pump used for the low-flow samples could have caused losses of VOCs by heating the well water, and (2) new low-density polyethylene (LDPE) tubing was used to collect the low-flow samples, which would cause some losses of VOCs due to sorption by the tubing (Parker and Ranney, 1998). However, neither reason would explain why the anion concentrations were also lower in the low-flow samples.…”

Use of Small-Diameter Bladder Pumps in Direct-Push Ground Water Monitoring Wells at the CRREL Site

“…In contrast, the PE pump had not been placed in the well until the day before the sampling event. Previous studies by our laboratory (Parker et al 1990;Parker and Ranney 1994, 1997, 1998 have shown that TCE is readily sorbed by the polymeric materials used in bladder pump systems (e.g., fluorinated ethylene propylene [FEP]), and that losses are greater at lower flow rates and with longer lengths of tubing. This assumption (that differences in concentrations may be the result of differences in sorption that resulted from differences in the materials used and equilibration times) is borne out by the fact that the differences between the concentrations were less with each sampling event.…”