Andy

You are indeed right TPH is just a name and is incorrectly used, but it is what the industry call it and that pretty much won't change as it is embedded (well for now anyway, a revolution can always be initiated). I am sure you use the term Granite when indeed it is most likely 'granitic' but not necessarily a granite sensu strict but is indeed a syenite or monzonite, this is also as they say in the deep south, 'just plain wrong'. :) Tit for tat, slightly misleading but people know what they mean. If you see what I mean. Similarly Sunny Delight and many 'orange juices' are not Orange Juice and are in fact luminescent kiddie crack.

I understand from the literature that Oak Leaves give the highest reading of all (leaves?) when contributing to 'TPH'. This organic interference has been my argument for a long time. A bit of organic matter and the results show that there is a contamination issue when indeed there is none. I have even tried to provide scientific literature to prove it along with photographs of said 'contamination' but if it is written down in the analyses most reject the obvious and say 'there's TPH in that though....'. Quite annoying really. Nevertheless we march on. 

Remember, next time you see a granitic rock - determine its mineralogy first.... :D and I'll determine

Cheers for the info though, much appreciated.

Russell



Russell Corbyn MRSC FGS
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-----Original Message-----
From: Contaminated Land Management Discussion List [mailto:[log in to unmask]] On Behalf Of Andy O'Dea
Sent: 19 July 2010 10:35
To: [log in to unmask]
Subject: Re: TPH analysis interpretation

***Comments from a colleague at PBA - Happy to pass on any further comments or queries***

The nub of this issue, and there are a couple of issues really, is as follows - the TPH-CWG method or whatever method derivative you care to choose, determines compounds over the carbon range ~C5-C44. Therefore compounds with a molecular weight greater than C44 or thereabouts will not be resolved. Heavy fuel oils, bitumens, ashphalts etc contain compounds which may have MWs in the thousands. C5-C44 is really a very narrow 'window' and for many (most?) real samples, this window does not in any way represent the majority of the compounds actually present. 
 
There is also a solubility issue as hexane or hexane acetone solvents may not be as 'aggressive' as say DCM or toluene but this is really secondary to the 'window' issue. So, by way of an example - in the old days, when the unfashionable toluene extract was used, you could easily get several per cent of  'extractable matter' in comparison to a PRO/DRO (broadly equivalent to the TPH-CWG) of say only a few hundred or thousand ppm.
 
We wish that the industry would just stop using the term TPH as it causes so much confusion and is just plain wrong. The only thing you can be absolutely sure of when you specify a TPH analysis is that you will not get the true total of the petroleum hydrocarbons present. None of the current methods gives a total and none is able to fully discriminate between petroleum and non-petroleum sources. The total petroleum hydrocarbon content of a sample is actually the sum of those compounds of carbon range C1 - Cn which are derived from crude oil. Therefore compounds not derived from crude oil such as those derived from coal, plant matter or animals - are not, by definition, petroleum hydrocarbons.
 
To illustrate this you could submit a sample of - grass, oak leaves, leaves in general, apple peel, lard, a pork pie, a biro and ask for a TPH analysis by any of the routine methods and you might be surprised by how contaminated with total petroleum hydrocarbons they all were.
 
All of the current methods are, to a greater or lesser extent empirical, that is their result is defined by the method parameters the laboratory set. Therefore when you specify a TPH analysis, what you actually get is a method defined Extractable Hydrocarbon result. Now don't mention haloforms - which contain carbon but may not of course contain hydrogen at all.

Regards

Andy O'Dea
Senior Associate

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