542F04010
Development of Analytical Methods for
Fuel Oxygenates
Through the Measurement and Monitoring Technologies for the 21st Century (21M2) initiative,
EPA's Office of Solid Waste and Emergency Response (OSWER) is identifying and supporting
deployment of promising measurement and monitoring technologies by matching existing and
emerging technologies with OSWER program and client needs in the fields of waste management
and site cleanup. OSWER has identified a number of "needs areas" as the focus of 21M2. These
needs reflect evolving requirements across all waste programs. A recent list and description of
needs is available at the 21M2 Internet site at httD://www.cluin.ore/Drograms/21m2/needs.cftn.
Background
EPA developed this fact sheet to summarize a recent
study funded in part by the 21 M2 program on the
analytical methods used for fuel oxygenates. The
study produced optimized protocols to preserve and
analyze groundwater samples for the suite of fuel
oxygenates commonly found at petroleum fuel release
sites. The most common of these oxygenates are
methyl tertiary-butyl ether (MTBE) and ethanol.
Other oxygenates include tertiary-amyl methyl ether
(TAME), ethyl tertiary-butyl ether (ETBE),
diisopropyl ether (DIPE), tertiary-amyl ethyl ether
(TAEE), tertiary-butyl alcohol (TBA), tertiary-amyl
alcohol (TAA), and methanol. More comprehensive
information on the topic and the waste program fact
sheet on the method are available from the Office of
Underground Storage Tanks (see "Project
Information").
Project Objectives
EPA evaluated the performance of modifications to
existing SW-8461 methods that are relevant to the
1 SW-846 is EPA's official compendium of analytical and
test methods that have been "evaluated and found to be
among those acceptable for testing under Subtitle C of the
Resource Conservation and Recovery Act (RCRA), as
amended." SW-846 is a guidance document that sets forth
acceptable, although not required, methods. Under the
Agency's Performance-Based Measurement System
approach as applied to waste sites, any method may be used
provided it can be demonstrated to detect the analyte(s) of
concern in the matrix of concern at the regulatory level of
concern.
analysis of MTBE and other oxygenates. Study
objectives were to:
identify the most feasible and cost-effective
analytical methods and optimum operating
conditions to analyze fuel oxygenates in water
with a target sensitivity of 5 u-g/L;
• collect information on performance of alternative
analytical methodologies;
• evaluate sample preservation techniques and their
influence on sample integrity;
disseminate the data from this study through
guidance documents; and
Recommend potential modifications to existing
SW-846 methods.
Project Results
Evaluation of Purge-and-Trap Followed by
GC/MS. One phase of the study involved evaluating
purge-and-trap (Method 5030B) and gas chromato-
graphy/mass spectrometry (GC/MS, Method 8260B)
on MTBE, TBA, DIPE, ETBE, TAME, and TAEE.
The results of this phase demonstrated that the most
consistent oxygenate recoveries are obtained when
samples are prepared using Method 5030B with a
heated (80° C) purge-and-trap and then subjected to a
determinative analysis using Method 8260B with a
DB-Wax capillary column. A RTX-Volatile capillary
column with a heated purge did not significantly
improve the overall method performance compared to
the performance using the DB-Wax capillary column.
In addition, BTEX interferences did not adversely
affect the chromatographic separation, quantitation,
and recovery of the oxygenates. If ethers are the only
target oxygenates of concern, then the sample need not
be heated to obtain 5 u.g/L detection limits.
SAt-2.
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Office of Superfund Remediation
and Technology Innovation
EPA/542/F-04/010
Use of Static Headspace and Trisodium
Phosphate Preservative. A second phase of the
study involved the use of static headspace (Method
5021) to prepare samples collected from two oxygen-
ated fuel release sites. Three different laboratories
analyzed the split samples from each site. Also tested
in this phase of the study was the ability of trisodium
phosphate, a sample preservative (used instead of
acid), to prevent acid-catalyzed hydrolysis of the
ethers during analysis at elevated temperature. All
samples exhibited good agreement between analyses
of MTBE, TAME, ETBE, and TBA (where present).
Refrigeration and chemical preservation, the key
components of sample preservation, are used to
prevent deterioration and degradation of groundwater
samples. Refrigeration effectively inhibits the
chemical deterioration of the sample, and chemical
preservation is necessary to prevent biodegradation.
Most protocols for the chemical preservation of
groundwater samples call for the addition of a suffi-
cient volume of hydrochloric acid to adjust the pH of
the sample to less than 2. However, under the high
temperature conditions of GC analysis, ethers undergo
acid-catalyzed hydrolysis inside the instrument. This
consumes ether and creates alcohol, giving false
results. Consequently, another objective of EPA's
investigation was to determine whether this effect was
significant under expected operating conditions for
oxygenate analysis and if so, to evaluate an
alternative. The study evaluated two sets of acidified
samples using heated purge-and-trap and GC/MS
analysis. For samples with a pH of 1 and 30 minutes
of incubation, more than 50 percent of the MTBE in
the sample was converted to TBA during passage
through the GC instrument.
The study found that ether hydrolysis can be avoided
by using a base rather than an acid as the chemical
preservative. However, the pH of the preserved
sample must exceed 11 to be effective. This alkaline
condition prevents the biodegradation of organic
compounds in the sample while avoiding potential
problems of acid-catalyzed ether hydrolysis. It also
eliminates the problem of effervescence in samples
with high carbonate alkalinity that is caused by acid
preservation.
To achieve the elevated pH, approximately 0.4 grams
of trisodium phosphate dodecahydrate ("TSP") is
recommended. The TSP is added to the sample vial
prior to sample collection. To avoid the need for a
scale in the field, the sample team in this project used
a pre-sized scoop that held a volume of TSP whose
weight is equivalent to 0.4 grams. Following the addi-
tion of the TSP, each vial was filled with groundwater
and sealed without headspace (the same as is done for
a sample preserved with acid). If purge-and-trap
(Method 5030B) is used to prepare the water samples,
it is particularly important and good laboratory
practice to prevent transfer of aerosols from the
purged water to the trap and GC column.
Project Information
A more detailed summary of the EPA study on the
analytical methods of fuel oxygenates is available in
Analytical Methods for Fuel Oxygenates, L.U.S.T.: A
Report on Federal & State Programs to Control
Leaking Underground Storage Tanks, New England
Interstate Water Pollution Control Commission,
Bulletin 42, October 2002.
httv://w\vw.eDa.ffov/swen4stl/mtbe/LL42Anatvtical.Ddf
The Office of Underground Storage Tanks has
prepared a fact sheet on "Analytical Methodologies
for Fuel Oxygenates," EPA 510-F-03-001. It is
available at:
http://www. eva. sov/oust/mtbe/omethods. pdf
For more information on this study, contact Barry
Lesnik, U.S. EPA Office of Solid Waste, 703-308-
0476, lesnik.barrv@eDa.gov.
Additional Information
More information can be found at the following
locations:
• Analytical methods.
EPA's Methods Information Communication
Exchange (MICE) hotline at 703-676-4690, or
visit the MICE website at
http;//www. epa. zov/SW-846/mice. htm
• SW-846 methods.
httt>://www. epq. eov/epaoswer/hazwaste/test/rnam.
htm
EPA's Office of Underground Storage Tanks.
htto://www. epa. sov/oust
21M2 program.
http://cluin.orff/Drofframs/2Jm2/
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