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Short answer
Total petroleum hydrocarbons (TPH) is a method-defined measurement of the hydrocarbon mass in a sample that a particular laboratory method can detect. ATSDR describes TPH as a term for a large family of several hundred chemical compounds that originally come from crude oil. A TPH number is only meaningful with its method and carbon range attached: EPA SW-846 Method 8015D, for example, defines gasoline range organics (GRO) as alkanes from C6 to C10 and diesel range organics (DRO) as alkanes from C10 to C28.
What TPH means
ATSDR’s ToxFAQs for TPH explains that TPH is not one substance. It is a mixture of compounds made mainly of hydrogen and carbon, and it is grouped into “petroleum hydrocarbon fractions” whose members behave similarly in soil and water. ATSDR names hexane, jet fuels, mineral oils, benzene, toluene, xylenes, naphthalene, fluorene and gasoline components among the compounds involved, and notes that any one sample is likely to contain only some of them. Some fractions float on water and form surface films, while others sink to bottom sediments.
Because the group is defined by what a method measures rather than by a fixed list of molecules, “TPH” on a lab report means “the hydrocarbons this method captured, within this range”. That is why the same site can produce different TPH values from two laboratories using different methods.
How TPH testing works: GRO, DRO and ORO
Most TPH testing (also searched as “total petroleum hydrocarbons test” or “total petroleum hydrocarbons testing”) reports fractions by carbon range rather than a single undifferentiated number. EPA SW-846 Method 8015D, Revision 4 (June 2003), uses gas chromatography with flame ionization detection (GC/FID) for nonhalogenated organics, including GRO and DRO. For the instrument side, see our guide to gas chromatography columns, carrier gases and detectors.
Gasoline range organics (GRO)
Method 8015D defines GRO as the range of alkanes from C6 to C10, covering a boiling-point range of approximately 60 to 170 degrees C. GRO is volatile, so the method introduces samples into the GC/FID by purge-and-trap (Methods 5030 and 5035), automated headspace (Method 5021), vacuum distillation (Method 5032) or another appropriate technique.
Diesel range organics (DRO)
Method 8015D defines DRO as the range of alkanes from C10 to C28, boiling at approximately 170 to 430 degrees C. Samples for DRO are prepared by an appropriate solvent extraction method, and the extract is injected into the GC/FID.
Oil range organics (ORO)
Heavier material above the DRO range is reported as oil range organics. Texas TX1005, as reported in a University of Tulsa conference presentation (IPEC 2019), reports a separate ORO fraction of C28 to C35 (see the table below). Method 8015D itself defines GRO and DRO only.
Method comparison: Method 8015D and TX1005 carbon ranges
The carbon boundaries differ between frameworks, which is the main reason numbers from different methods are not interchangeable.
| Fraction | EPA SW-846 Method 8015D | Texas TX1005 (as reported by IPEC 2019) |
|---|---|---|
| GRO | C6 to C10 alkanes, about 60 to 170 degrees C | C6 to C12 |
| DRO | C10 to C28 alkanes, about 170 to 430 degrees C | C12 to C28 |
| ORO | Not defined in the method text | C28 to C35 |
Oklahoma DEQ’s risk-based levels guidance describes TPH as typically C6 to C35 and recommends TCEQ Method 1005 for preliminary soil and groundwater characterization. Status note: EPA’s Method 8015D page states the method is validated and available for use but not formally incorporated into the SW-846 compendium, and lists it in its Selected Analytical Methods (SAM) for DRO, GRO and kerosene.
Reading a TPH result: a checklist
- Which method and revision? Look for the method number (for example 8015D or TX1005) on the report.
- Which carbon range? Compare the reported range to the table above; C6 to C10 and C6 to C12 are not the same GRO.
- Fraction or total? Check whether the lab reports GRO, DRO and ORO separately or sums them.
- Compound-specific or not? Method 8015D notes that the FID is a non-selective detector, so many non-target compounds in a sample can interfere. A GC/FID TPH value does not identify individual compounds such as benzene.
- Fuel identification caution. Method 8015D states that identifying specific fuel types can be complicated by evaporation, biodegradation and other environmental processes.
- Sample handling. Confirm that the preparation route matches the fraction: volatile GRO by purge-and-trap or headspace, DRO by solvent extraction.
How does petroleum affect the human body?
Effects depend on which compounds are present, and ATSDR states that exposure to TPH can affect different body systems. At high air levels, some compounds can affect the central nervous system, causing headache and dizziness; one compound is associated with peripheral neuropathy; others affect blood, the immune system, lungs, skin and eyes. In animal studies, effects have been reported in the lungs, central nervous system, liver, kidney, and in reproduction and development. IARC has classified benzene as carcinogenic to humans, and benzo[a]pyrene and gasoline as probably and possibly carcinogenic respectively, according to ATSDR. People can be exposed through gas-station air, chemical use at home or work, contaminated water or soil, certain occupations, or living near a spill or leak. This is general information, not medical advice.
What are examples of petroleum products?
ATSDR names gasoline, jet fuel, kerosene and mineral oils as products containing TPH, along with specific compounds found in them such as hexane, benzene, toluene, xylenes, naphthalene and fluorene. The fractions above map loosely to product types: GRO covers the gasoline range and DRO the diesel range, which is why the method is used for fuel releases.
What is hydrocarbon oil used for?
The sources cited here do not provide a use list for hydrocarbon oils beyond naming fuels (gasoline, jet fuel, kerosene) and mineral oils as TPH-containing products, so this page does not extend it. For chemical compatibility of lab materials with petroleum oils and fuels, see the chemical compatibility chart for wetted materials.
Common misunderstandings
- “TPH is a single chemical.” It is a family of several hundred compounds (ATSDR), and a sample usually has only some of them.
- “A TPH number tells me what compounds are present.” It does not; FID is non-selective. Compound-specific work needs a different measurement. See GC-MS vs LC-MS for how mass-spectrometric detection differs.
- “All labs define GRO and DRO the same way.” Method 8015D and TX1005 use different carbon boundaries.
FAQ
What does TPH stand for?
Total petroleum hydrocarbons. “TPH” appears on lab reports and in ATSDR materials as shorthand for the measured group of petroleum-derived hydrocarbons.
What is a total petroleum hydrocarbons test?
A laboratory analysis, commonly GC/FID under a method such as EPA 8015D, that quantifies petroleum-derived hydrocarbons in soil, water or other media, usually by GRO, DRO and sometimes ORO fractions.
What are the four types of hydrocarbons?
The sources used here do not classify hydrocarbons into four types, so this page answers in the framework they do use: the carbon-range fractions GRO, DRO and ORO.
Sources
- ATSDR, ToxFAQs for Total Petroleum Hydrocarbons (TPH), wwwn.cdc.gov, read 2026-11-07.
- U.S. EPA, SW-846 Method 8015D, Nonhalogenated Organics Using GC/FID, Revision 4, June 2003, epa.gov, read 2026-11-07.
- Oklahoma DEQ, Risk-Based Levels for TPH, deq.ok.gov, read 2026-11-07.
- University of Tulsa, IPEC 2019 presentation (G. Lull), cese.utulsa.edu, read 2026-11-07.
