Northwest Total Petroleum Hydrocarbon

Analytical Decision Tree

The following flow chart depicts the laboratory analytical scheme to be used when analyzing samples. The first step is the qualitative determination of the existence and nature of petroleum contamination and this should be used when the site contamination is unknown. It is required that this first step will be performed on a representative sample from the area that is suspected to be the most contaminated at the site. For those samples containing analytes which, due to their retention times, ratios to each other or their non-hydrocarbon pattern (e.g., creosote), do not suggest petroleum hydrocarbons, then GC/MS methods should be employed to ascertain the components. At those sites where the petroleum contaminants are known or have been identified using the NWTPH-HCID method, the specific product method is to be used.

Analytical Methods:

• NWTPH-HCID: NWTPH Hydrocarbon Identification

This is a qualitative and semi-quantitative screen to determine the presence and type of petroleum products that may exist in water or soil. This method should be used if the type of petroleum contamination is unknown. It should be performed on contaminated soil or water that is representative of the contamination at the site. The results of this method will determine which fully quantitative method/methods, if any, are to be used in determining compliance with the matrix criteria. Should the value of the analysis for gasoline, diesel, or heavy oils (or any other identified petroleum product) exceed the reporting limits, then the specific analytical method for that product must be employed.

• NWTPH-Gx: NWTPH Gasoline Range Hydrocarbons

This is the qualitative and quantitative method for volatile petroleum products in soil and water. Petroleum products applicable for this method include aviation and automotive gasolines, mineral spirits, stoddard solvent, and naphtha.

• NWTPH-Dx: NWTPH Diesel/Lube Oil Range Hydrocarbons

This is the qualitative and quantitative method for semi-volatile petroleum products in soil and water. Petroleum products applicable for this method include jet fuels, kerosene, diesel oils, hydraulic fluids, mineral oils, lubricating oils and fuel oils.