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,��E° QTFS Underground Storage Tanks Fact Sheet Analytical Methodologies for Fuel Oxygenates What is the purpose of this fact sheet? This fact sheet provides information for state and federal regulators, laboratory analysts,consultants, and contractors about EPA's validated analytical methods for common fuel oxygenates. What are fuel oxygenates? Fuel oxygenates are primarily ethers and alcohols specifically added to gasoline to increase the octane content, promote cleaner burning in gasoline engines,and/or improve other performance characteristics. The most common fuel oxygenates are methyl tertiary-butyl ether(MTBE)and ethanol. Other fuel oxygenates include: tertiary-amyl methyl ether(TAME),ethyl tertiary-butyl ether(ETBE),diisopropyl ether()IPE),tertiary-amyl ethyl ether (TAEE),tertiary-butyl alcohol(TBA),tertiary-amyl alcohol(TAA), and methanol. How widespread is fuel oxygenate contamination? Fuel oxygenates may be present at any underground storage tank(UST) site because different combinations of oxygenates in varying concentrations have been used in gasoline for more than 30 years. Oxygenates may also occur as unintentional components of other fuels (for example diesel fuel,jet fuel,and heating oil). What methods are available to analyze for oxygenates? Analytical methods for petroleum hydrocarbons(usually benzene,toluene,ethylbenzene, and the isomers of xylene, or collectively`BTEX")are well established and some of these protocols have been"modified"to include oxygenates as individual target compounds. Until recently,however,validated EPA analytical methods existed for only a few of the oxygenates that may be present in fuel(specifically ethanol,methanol, and TBA). What potential problems may occur if hydrocarbon methods are used for oxygenate analysis? Methods which were developed for analysis of petroleum hydrocarbons in water samples may or may not be appropriate for fuel oxygenates. Potential problems associated with non-validated methods include: 1. Analytical instruments are not routinely calibrated for oxygenates- Conventional analytical procedures designed for petroleum hydrocarbons have the capability to detect MTBE and the other ethers,but they are rarely calibrated for the fuel oxygenate ethers (other than MTBE). 2. Inappropriate methods may be used for sample analysis-Method 8021 (GC/PID)cannot be regarded as a consistently reliable analytical tool for the analysis of oxygenates because it is unable to detect alcohols and most ethers and it may yield either false positives or false negatives for MTBE. These problems are primarily due to coelution interferences and to the high ionization energies of many oxygenates. Method 8015 (GC/FID)can detect oxygenates at low concentrations,but it cannot provide positive confirmation of the chemical identity of the analyte that is detected. Therefore, compounds that coelute may be mistaken for one another leading to over-or under-reporting of actual concentrations of the oxygenate compounds. 3. Detection limits (particularly for alcohols)may be higher than regulatory standards -Because alcohols are so highly soluble in water, extracting them for analysis is difficult and reporting limits are generally much higher than those for BTEX and MTBE. In order to consistently achieve low detection levels for TBA(and other alcohols), sample preparation procedures must be modified to increase method sensitivity. 4. Hydrolysis of ethers and formation of alcohols-Acid-catalyzed hydrolysis(breakdown)of ethers may occur during analysis,particularly if the samples are heated to improve the extraction efficiency for alcohols. This can lead to underreporting of the ether(for example MTBE) concentration and overreporting of the concentration of the corresponding alcohol(which is TBA if the ether is MTBE).