Method NWTPH-Gx

Volatile Petroleum Products Method for Soil and Water, by GC/FID


The NWTPH-Gx method is intended to replace the Oregon’s TPH-G and Washington’s WTPH-G methods and to present a more comprehensive approach to volatile petroleum product analyses. NWTPH-Gx adapts Oregon’s TPH, Washington’s WTPH and EPA SW846 Methods 5030 and/or 8020 and covers the quantitative and qualitative analyses of volatile petroleum products, e.g. gasolines, naphtha, mineral spirits, stoddard solvent, and other volatile petroleum products in soil and water.

Gas Range Organics (GRO) corresponds to the range of alkanes from C6 to C10 and covering a boiling point range of approximately 60EC – 170EC.

Soil samples are extracted with methanol and analyzed by gas chromatograph with a flame ionization detector (GC/FID). The methanol extracts may be injected directly into the GC or they may be diluted with organic free reagent water and introduced by a purge/trap concentrator. Water samples are introduced directly to the purge/trap concentrator. This method specifies the criteria for the identification and quantitation of volatile petroleum products. When the type of petroleum product is unknown, regular unleaded gasoline will initially be used as the default petroleum standard.

The use of GC/PID, GC/MS or GC/AED (Atomic Emission Detector) for the analysis of gasoline may be substituted for GC/FID as long as all other method parameters are met.

– Oregon’s Department of Environmental Quality TPH-G and Washington’s Department of Ecology WTPH-G methods.

Method Data


Analyte List


*Please contact our project management team for more information about reporting limits and other specific project needs.

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