Detection of Natural Organic Matter in the Total Petroleum Hydrocarbon Method
Graham Corban from Hill Laboratories recently co-authored an article on the Total Petroleum Hydrocarbon method, with a specific focus on the implications of Natural Organic Matter being present in samples for Total Petroleum Hydrocarbon analysis. The article was prepared for the Wasteminz Contaminated Land Sector Group.
A summary of the paper is below, and you can read the full paper here.
When people order a Total Petroleum Hydrocarbon (TPH) test in soil or water, they would be well within their rights to think that the results they get back would be precisely that - the sum of all hydrocarbons present originating from a petroleum source. However, that's not the case for the TPH test. In fact, the TPH name is somewhat of a misnomer. The results are usually reported as carbon bands between C7 (n-pentane) to C36 (n-hexatriacontane). Therefore, it cannot be considered a true total because hydrocarbons lighter than C7 and heavier than C36 are excluded.
In addition, non-hydrocarbon synthetic organic compounds such as pesticides and polychlorinated biphenyls (PCB) can also be detected if present at high enough levels, and these compounds are not petroleum in origin or true hydrocarbons either.
The test can also detect Natural Organic Matter (NOM) which are compounds such as plant based resins, oils and natural hydrocarbons.
The downside of the detection of NOM and thinking that it is petroleum based is that perfectly good productive soil can sometimes be unnecessarily sent to landfill. Fortunately though, a close examination of the TPH chromatogram in combination with further GCMS analysis of the extract will allow an experienced analyst to differentiate the source of the contamination.
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