A Comparison between EPA Compendium Method TO - 15 and EPA Method 8260 B for VOC Determination in Soil Gas

Evaluations of vapor intrusion pathways of chemical contaminants often include soil gas measurements to assess the potential for indoor inhalation. No longer just a screening tool, soil gas measurements are requiring a level of quality and defensibility which should be incorporated in soil gas analytical protocols. While both EPA Compendium Method TO-15 and EPA SW-846 Method 8260B are routinely used for the analysis of Volatile Organic Compounds (VOCs) in soil gas, neither method has been validated for the soil gas matrix. To determine comparability of the two methods, the precision and accuracy of EPA SW-846 8260B are compared to EPA Compendium Method TO-15. Using reference standards prepared to simulate expected soil gas humidity levels, the two methods are compared post-collection through analysis. Additionally, real field samples are analyzed by each method to compare performance. Comparative results are generated using both GC/MS full scan and SIM mode and the limitations of each approach are discussed. Finally, recovery of VOCs through a TO-15 soil gas sampling train is evaluated at several sampling temperatures. The specific VOCs evaluated in the study are Vinyl Chloride, Benzene, Trichloroethene and Naphthalene.