[Gasoline Oxygenates] what mtbe merl leap isco iron home
Approach Method Questions Applications Field Sites

Approach

The current concern over contamination of groundwater by MTBE has increased the need for a better understanding of the processes that control its environmental fate. As part of an ongoing study to characterize the kinetics and mechanisms of MTBE degradation, we have developed a direct aqueous injection (DAI) GC/MS technique that allows us to simultaneously determine for MTBE and its expected products (TBA, TBF, isopropanol, and acetone) at the sub-ppb level in water.


The DAI-GC/MS Method

Currently, most analyses for MTBE in water are performed using conventional purge-and-trap methods. Most of the expected degradation products of MTBE, however, have lower Henry's gas law constants than the parent compound, making conventional purge and trap methods unsuitable for simultaneous analyses of both parent and products at low concentrations. In order to perform simultaneous analyses, we developed a direct aqueous injection (DAI) technique using gas chromatography with a highly polar column and detection by mass spectrometry (GC/MS). Minimum detection limits for the analytes tested to date are shown on the right (in µg/L). (Church, et. al., 1997) Analyte
MTBE
ETBE
TAME
TBA
TAA
TBF
Acetone
IP
MA
MDL
0.1
0.1
0.1
0.1
0.1
5.0
<10
40
40

Frequently Asked Questions about the Method


Applications

A series of chromatograms obtained with the DAI-GC/MS method, which demonstrate the advantage of detecting MTBE degradation from product appearance. The data are for an effluent from a soil column before (front) and after (middle) the onset of biodegradation. A 40 µg/L standard (back) is shown for reference. Note that the 44 day chromatogram shows a positive indication of MTBE degradation through the appearance of TBA even though it is not yet apparent from the disappearance data. (Church, et. al., In prep.)

Collaborators with Field Sites

To explore what can be learned from the DAI-GC/MS method, we are collaborating with a variety of research groups who are doing (extensive or intensive) studies of MTBE occurence in the environment. Usually, we analyze for trace levels of MTBE degradation products while others do the parent compound using standard P&T methods. All collaborators to date are shown here. We welcome inquiries from potential collaborators with access to significant study sites.

  • James Landemeyer, USGS, Reston, VA.
  • James Barker, University of Waterloo, Ontario, Canada.
  • Mario Schirmer, University of Waterloo, Ontario, Canada.
  • Rick L. Johnson, Oregon Graduate Institute, Portland, OR
  • Arthur Baehr, USGS, Trenton, NJ.
  • Mary Ann Thomas, USGS, Chicago, IL.
  • Joseph Domalgalski, USGS, Sacramento, CA
  • Steve Maddox, Maddox & Associates, La Habre, CA.
  • John Zogorski, USGS, Rapid City, SD.

Publications


Acknowledgements

Major Funding for this work has come from:


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