Quantification and Interpretation of Total Petroleum Hydrocarbons in Sediment Samples by a GC/MS Method and Comparison with EPA 418.1 and a Rapid Field Method Guibo Xie, Michael J. Barcelona,* and Jiasong Fang Department of Civil and Environmental Engineering, The University of Michigan, Ann Arbor, Michigan 48109-2099 Total petroleum hydrocarbons (TPH) as a lumped param- eter can be easily and rapidly measured or monitored. Despite interpretational problems, it has become an accepted regulatory benchmark used widely to evaluate the extent of petroleum product contamination. Three currently used methods (GC/ MS, conventional EPA 4 1 8 .1 , and a rapid field method PetroFLAG) were performed to quantify the TPH content in samples collected from a site contaminated by transformer oil. To standardize the method and improve the comparability of TPH data, crucial GC-based quantification issues were examined, e.g., quantification based on internal standards (ISTD) vs external standards (ESTD), single vs multiple ISTD, and various area integration approaches. The interpretation of hydrocarbon chromatographic results was examined in the context of field samples. The performance of the GC/ MS method was compared with those of EPA 418.1 and PetroFLAG. As a result, it was observed that the ISTD quantification method was preferred to the ESTD method, multiple ISTD might be better than single ISTD, and three different area integration approaches did not have a significant effect on TPH results. Evaluation of the chro- matograms between a reference sample and three un- known samples showed that the extent of contamination varied appreciably with sample depth. It was also found that there existed a good positive correlation between GC/ MS and both EPA 418.1 and PetroFLAG, and that EPA 4 1 8 .1 produced the higher overall estimate while GC/ MS and PetroFLAG resulted in lower, more statistically comparable TPH values. Crude and refined petroleum products constitute a major class of contaminants that environmental professionals are likely to encounter in conventional or environmental forensic site investiga- tions and remediations. Compared to time-consuming, complex separation methods identifying individual compounds in weath- ered petroleum products, total petroleum hydrocarbons (TPH) as a collective parameter can be relatively easily and rapidly measured and monitored. TPH is, thus, an accepted regulatory benchmark widely used to evaluate petroleum contamination by environmental professionals. The Association for the Environ- mental Health of Soils (AEHS)’s eighth annual survey of states’ cleanup standards for hydrocarbon-contaminated soil and ground- water has been published recently. 1 By 1998, all 50 states had set site cleanup standards or guidelines based on TPH measurements by various methods. These methods may include specific deter- mination of known toxic fractions (e.g., benzene, toluene, ethyl- benzene, xylene (BTEX), methyl tert-butyl ether (MTBE), and/ or polyaromatic hydrocarbons (PAHs)). Methods of measuring TPH and its components have been explored extensively. Currently a variety of analytical methods are used to measure TPH due to the complicated composition of petroleum mixtures. No single method, however, can be used as a representative, nonspecific procedure for TPH measurement. TPH measurements generally include several crucial steps: retention of volatile <C 8 compounds and selection of an appropri- ate solvent or mixture of solvents to extract the petroleum hydrocarbons from environmental samples; preparation of calibra- tion standards by mixing petroleum products or specific hydro- carbons in a proper ratio; and instrumental analysis of the calibration standards and sample extractions. All of these steps may result in selective capture of individual components of hydrocarbon mixtures. Major problems can arise in risk-driven site cleanup decisions. This is because environmental or human health risk may arise from various subfractions or specific components of petroleum hydrocarbon mixtures, which are not selectively determined by some TPH methods. 2 Various approaches to instrumental analysis allow us to classify the TPH methods into (a) gravimetric, EPA 413.1, 3 method 9070; 4 (b) spectroscopic, EPA 418.1, 5 PetroFLAG; 6 (c) gas chromatog- raphy, methods 8015B, 7 NWTPH; 8 (d) others, 1 H and 14 C nuclear * Corresponding author: (tel) (734) 763-9666; (fax) (734) 763-6513; (e-mail) mikebar@ engin.umich.edu. (1) Judge, C.; Kostecki, P.; Calabrese, E. Soil Groundwater Cleanup 1998 , (May) 11-31. (2) Hutcheson, M. S.; Anastas, N.; Fitzgerald, J.; Locke, P.; Rose, J. Soil Groundwater Cleanup 1999 , (Dec/ Jan), 31-33. (3) Environmental Protection Agency, Method 413.1, EPA 600/ 4-79-020. (4) Environmental Protection Agency, Test Method for Evaluating Solid Waste, EPA SW-846, 3rd ed.; the U. S. Government Printing Office (GPO), Washington, DC, 1996. (5) Environmental Protection Agency, Methods for Chemical Analysis of Water and Wastes; Government Printing Office: Washington, DC, 1983. (6) Dexsil Corp. PetroFLAG  Hydrocarbon Analyzer User’s Manual; Hamden, CT, 1995; pp 4-16. (7) Uhler, A. D.; Stout, S. A.; McCarthy, K. J. Soil Groundwater Cleanup 1998 , (Dec/ Jan), 13-19. Anal. Chem. 1999, 71, 1899-1904 10.1021/ac981244t CCC: $18.00 © 1999 American Chemical Society Analytical Chemistry, Vol. 71, No. 9, May 1, 1999 1899 Published on Web 04/03/1999