Comparison of downhole and surface sampling for the determination of volatile organic compounds (VOCs) in ground water

Ground Water Monitoring Review
By: , and 

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Abstract

The relative precision and accuracy of sampling and analysis methods for the determination of trace concentrations of volatile organic compounds (VOCs) in ground water were compared. Samples were collected from a well containing nanogram‐per‐liter (ng/L) to microgram‐per‐liter (μg/L) levels of VOCs. A Keck helical rotor submersible pump was used to collect samples at the surface for analysis by purge and trap (P&T) and for analysis by adsorption/thermal desorption (ATD). Downhole samples were collected by passing water through an ATD cartridge. Although slight spontaneous bubble outgassing occurred when the water was brought to the surface, the relative precisions and comparabilities of the surface and downhole methods were generally found to be equivalent from a statistical point of view. A main conclusion of this study is that bringing sample water to the surface for placement in VOC vials (and subsequent analysis by P&T) can be done reliably under many circumstances. However, care must still be taken to prevent adsorption losses and cross contamination. Samples subject to strong bubble outgassing will need to be handled in a special fashion (e.g., by downhole ATD) to minimize volatilization losses. Additionally, the higher sensitivity of the ATD method allows lower detection limits than are possible with P&T. For example, several compounds present at the ng/L level could be determined with confidence by ATD, but not by P&T.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Comparison of downhole and surface sampling for the determination of volatile organic compounds (VOCs) in ground water
Series title Ground Water Monitoring Review
DOI 10.1111/j.1745-6592.1992.tb00418.x
Volume 12
Issue 1
Year Published 1992
Language English
Publisher Wiley
Contributing office(s) New Jersey Water Science Center
Description 8 p.
First page 126
Last page 133
Country United States
State New Jersey
City Gibbstown
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