WEF Discussion Forums
Laboratory Management and Technical Issues
Testing of Fat, Grease, Oils including vegtable, petroleum, and systhetic
Is there a good source of material that will describe the interpretation of testing results and the relationship of the results from the Hexane method of Oil and Grease (HEM) including the silica gel modification (SGHEM)and Total Petroleum Hydrocarbons(TPH), extractable petroleum hydrocarbons(EPH), volatile petroleum hydrocarbons)VPH), poly aeromatic hydrocarbons(PAH), and what appears to be a long list of parameters represented by numerous letters. Additionally do any of these quantify the synthetic oils used in industry and the automotive industry.
I don't know the answers to all of your questions; but, since I performed hundreds of "oil and grease" tests in the distance past I thought I would at least respond. My guess is that "Standard Methods" might be the most valuable source for some of your questions, although I suspect it won't offer comparisons of the results for all of the possible methods that you have listed. My own work in testing for "oil and grease" started in the 1960's when I was a "junior" chemist at Union Oil Company. We performed extractions using carbon tetrachloride on water samples that had petroleum contamination. The advantage to using a solvent that was heavier-than-water was that you didn't have to drain the water off first, before you got to the solvent/oil layer.
A couple of years later found me working at a lab at the Port of Los Angeles, where I did occasional "oil and grease" tests using "mixed hexanes" as the extracting solvent with the soxhlet device. Most of the samples were of fish cannery waste waters with pretty high concentrations of "Oil and grease." Of course, at about this time, the EPA was being formed, and scientists discovered that carbon tetrachloride, which had been used in the dry cleaning and industrial businesses for decades was fairly carcinogenic. So, using it became a "no-no" In fact, you could buy carbon tet in any market for use in spot cleaning your clothes at home. Interestingly enough (at least to me) my boss at the Port of LA lab, Mr. Carroll Wakeman, had worked with Dr. Richard Pomeroy in developing the hexane extractable test for oil and grease in the 1940's. They are not mentioned in my 17th Edition of Standard Methods, but I recall seeing lots of lab books with test data on Oil and Grease. As a side note, Dr. Pomeroy also developed the "methylene blue" field test for sulfide in water, listed as Method 4500-D, in the 1930's. I used that test for quite a few years at the Port lab, and later built a kit for use after I left the Port.
As the years went on I would occasionally see references to the EPA changing the O&G method for one reason or another. Which always has raised an internal chuckle with me. They used Freon for awhile, but then Freon became a "toxic chemical," so it's a "no-no." Then, it was back to hexane, either or without diatomaceous earth. As permit limits have tightened over the years, and as even more is expected of dischargers, the EPA has been ever-more diligent with lab certification and requiring that labs produce perfect results that get the "correct answer" no matter what. All this causes great grief to you folks that have to answer to the lab control freak agencies (glad I don't have to participate).
Now, how about the BOD test?
Anonymous No. ___
Jeff Naumann, old guy
Why don't we get a chance to edit these posts, at least within some short period of time.
I keep forgetting that I'm now anonymous; and, forget to mention WHICH anonymous I am.
The 1664A method states the following: "Extractable materials that may be determined are relatively non-volatile hydrocarbons, vegetable oils, animal fats, waxes, soaps, greases, and related materials." Because what the 1664A method defines "oil & grease" as what can be extracted using hexane as the solvent it may extract additional materials OR not extract items of interest to you. Using GC methods such as GC FID for TPH or PAHs will certainly give you more accurate and detailed results of your sample but are more expensive and time consuming analyses.
Hope that helps a bit.
As the last poster mentioned, the O&G test is a very direct way of measuring a host of different species in water. It's a method defined test: in other words, it does not measure one or even a class of well characterized entities such as cadmium (well defined) or PAHs (well defined) but a group of entities which are defined as extractable from water using hexane (or a solid phase pad) and then do not evaporate when you heat them to 70C.
EPH, VPH, EPH, PAH etc all measure a subset of the petroleum hydrocarbons present in a sample. Depending on how you plan to use the data, this subset can be a surrogate for the whole set: if for example you know that your hydrocarbon source always contains 20% (or 5% or whatever) of PAHs then you can measure the PAHs only and just multiply up. Most hydrocarbon sources are not constant (exceptions: tightly controlled manufactured products or fresh crude oil from a specific oil field) and so this surrogate argument does not hold up well.
So in short there is not a well defined relationship between the various measures of HC.
Your specific question about synthetic oils. Sometimes they are, or contain, hydrocarbons which would respond to EPH VPH etc. Sometimes they are esters which woud not respond to those tests but might well, depending on extractability and volatility, respond to the O&G test. So the short answer there is: it depends.
The final rule published on May 14, 1999 may have some information that you are seeking. I think it is attachedto my posting.