Analysis of Fuel Oxygenates Using the Eclipse Purge-and-Trap Sample Concentrator

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Analysis of Fuel Oxygenates Using the Eclipse Purge-and-Trap Sample Concentrator

Laura Chambers

Oxygenates are gasoline additives designed to boost octane rating and make fuel burn more cleanly. The US EPA recognizes Method 8260 (GC/MS) as the most appropriate determinative method for oxygenates in environmental matrices, and purge and trap (P&T) is cited as the most appropriate sample preparation technique. When oxygenates are added to these previously standardized methods, it is not necessary to change the GC/MS method at all, and only very minor changes to the P&T step are needed.

To optimize the P&T conditions, experiments were designed to test the effects of two variables that could be easily modified without making fundamental changes to the typical P&T method. Using a standard containing MTBE, TBA, and three other common oxygenates, duplicate aliquots of three sample sizes (5 mL, 10 mL, and 25 mL) were analyzed at each of four sample temperatures (ambient, 35, 45, and 60 C).

Once the optimum conditions were determined, an eight-point calibration curve was run covering a range from 0.2 to 200 ppb (1 to 1,000 ppb TBA) and a statistical MDL study was performed by analyzing seven replicate aliquots of a 0.5-ppb standard (2.5-ppb TBA). Finally, to demonstrate instrument performance on a real-world sample, tap water was spiked with 1-ppm unleaded gasoline and 100-ppb oxygenates, and analyzed using the recommended conditions.

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151 Graham Road
College Station, TX, 77842-9010