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Office of Solid Waste and Emergency Response EPA 510-F-03-001 Office of Underground Storage Tanks April 2003 (5401 G) www.epa.gov/oustimtbe/omethods.pdf What steps may be taken to address potential analytical problems with oxygenate analysis? 1. Routinely calibrate analytical methods for the suite of common fuel oxygenates-Calibration of analytical instruments for the suite of common fuel oxygenates can be adopted as part of the laboratory's standard operating procedures. Even when using EPA methods,EPA encourages flexibility in selecting target analyte lists that are tailored to site-specific conditions. 2. Use appropriate methods for sample analysis-For example,determinative methods evaluated in EPA's study that are capable of identifying fuel oxygenates at 5,ll g/L.or lower in fuel-contaminated groundwater samples include Method 8260(GC/MS)and Method 8015 (GC/FID). However,Method 8260 confirms the chemical identity of the analyte detected while Method 8015 does not. 3. Modify sample preparation methods to increase sensitivity and decrease detection limits-To increase the sensitivity of the method and lower the method detection limit,samples can be heated during the preparative phase. Heating is particularly important for preparing samples to be analyzed for alcohols,however, samples to be analyzed for ethers may be prepared at room temperature. EPA recently completed a method evaluation study which found that for Method 5030(purge-and-trap)and Method 5021 (static headspace),heating samples to 80°C for 30 minutes could consistently result in a detection limit of 5,ll g/L or lower for MTBE,TBA, ETBE,TAME, TAEE, TAA,DLPE,and acetone.Note,however,that heating acidified samples will hydrolyze ether to alcohol and,therefore,the chemical preservation method must be changed as described in#4 below. 4. Change the chemical preservation method to avoid the potential for ether hydrolysis- Gmundwater samples to be analyzed for hydrocarbons in addition to fuel oxygenates must be preserved using both a chemical preservative and refrigeration(preferably to 4° C)and also analyzed within prescribed holding times (generally 14 days or less). Acid is the most commonly used chemical preservative as it is effective in preventing biodegradation in the sample when the pH is less than 2. Acid may be used to preserve groundwater samples to be analyzed for ethers(and BTEX)if the preparation is conducted at room temperature. However,when acidified samples are heated to 80° C (which is necessary if alcohols are the target analytes) during the preparative phase (as with Methods 5030 or 5021),ethers present in the sample will hydrolyze. An alternative to chemical preservation with acid, and consequent avoidance of ether hydrolysis,is base preservation to raise the pH to greater than 11. The high pH is as effective in preventing the biodegradation of organic compounds in the sample as is a low pH,but the elevated pH has no adverse chemical effect on hydrocarbons or fuel oxygenates. Trisodium phosphate dodecahydrate("TSP")has been determined to be effective and safe for this purpose. TSP may also be used to neutralize acid-preserved samples prior to analysis, if an elevated temperature sample preparative method is to be used. Where can I get additional information? For additional information about analytical methods,call EPA's Methods Information Communication Exchange (MICE)hotline at 703-676-4690,or visit the MICE web site at http://www.epa.gov/SW-846/mice.htm. For information about the underground storage tank program,visit http://www.epa.gov/oust. More details on the issues discussed in this fact sheet and EPA's analytical methods study are available in the October 2002 issue of LUSTLine(Bulletin#42). The article, "Analytical Methods for Fuel Oxygenates",is accessible on the internet at http://www.epa.govloust,lmtbeILL42Analytical pdf.