The term TPH (Total Petroleum Hydrocarbons) is a confusing one, and often misunderstood by the non-conversant as being a fixed definition of a petroleum product that can be measured absolutely, and hence be directly compared with other TPH values. Unfortunately this is not the case.
In short analysis of the total petroleum hydrocarbon (TPH) content of soil and water samples is complex and confusing.
Definition of TPH “Total petroleum hydrocarbon is the measure of the concentration or mass of petroleum hydrocarbon constituents present in a given amount of soil or water. The word "total" is a misnomer--few, if any, of the procedures for quantifying hydrocarbons can measure all of them in a given sample. Volatile ones are usually lost in the process and not quantified and non-petroleum hydrocarbons sometimes appear in the analysis3”.
The problem of TPH analysis stems from the complicated nature of petroleum products which can be complex mixtures of hundreds of hydrocarbon compounds, with the exact composition varying due to a number of factors including the crude oil source and the subsequent refining process. To complicate this even further are the changes to the refined product/spilled material caused by weathering once exposed to environmental conditions.
It is also worth noting that here are a number of other terms that are often used in conjunction with TPH:
- EPH = Extractable Petroleum Compound,
- DRO=Diesel Range Organics,
- GRO=Gasoline Range Organics
- EDRO=Extended Diesel Range Organics,
- SVOCs=Semi Volatile Organic Compounds with TPH being the sum of the aliphatic and aromatic compounds in the GRO and DRO and mineral ranges.