[PeaGreen36]

Is it possible to extract TPH from fats such as butter/milk, without losing any of the ali/aros in the process?

[Arkcon]

Please define you acronym from the start.  Telling us later, or just telling us to Google doesn't make you smarter.

Please tell us the scale and application -- do you want some sort of analytical application, or product for further steps, or are you isolating for consumption.

Please trouble yourself to read our forum rules, we don't do that last one here.

[PeaGreen36]

Sorry - I didn't see the rules before posting, I read them a little too late 


Please consider this my new OP:   

TPHs, which are total petroleum hydrocarbons, such as diesels/oils etc, encompass both aliphatic and aromatic (ali/aro) hydrocarbons.

I am interested in extracting them from fats such as butter/milk for an analytical application. Although there are currently no regulation limits for these compounds in foods, the fumes given off by cars etc. is seemingly ever-increasing, so it would be interesting to see whether the more volatile TPHs are entering our food chain. (I have recently moved from environmental to food/feed analysis, so have chosen a project to get me used to the more difficult matrices encountered.)

I have tried extractions in hexane and silica gel+hexane (the latter working on some oily matrices); but these either don't strip away enough fat, or strip away too many of the aliphatic compounds. I think this is due to the polarity? (Please correct me if I'm wrong...)

[rolnor]

It seems hard to extract these lipophilic compunds separate from lipids? You have hormones like estrogen etc.?
I wonder why you want to extract them, if you want to analyze you can run LC//MS on the body fluid?

[pgk]

Furthermore, absorbed hydrocarbons will be metabolized in the liver and only their metabolites might be detected in animal/human fats or body fluids.
So, you have to search for hydrocarbons metabolites, too.
Roughly, aliphatic hydrocarbons are metabolized in the liver, to diketonic products (α-,ω- diacetyl derivatives) and aromatic hydrocarbons to phenolic derivatives and/or α-aryl alkanols. However, various other metabolites might be formed, depending on the particular hydrocarbon, as well as on the particular animal’s metabolic pathway.

[RedViper9]

Isolation is, at best, non-trivial. Since the identities of many petroleum products and their metabolites are known, I would work to determine the concentration of these molecules in milk samples using a triple quadrupole mass spectrometer.

[Arkcon]

Also, look into EPA analytical methods.  As was said, you basically can't purify everything you want away from everything you don't, then analyze.  You are instead interested in "markers" certain easily analyzed compounds that will allow you to extrapolate overall contamination.

[pgk]

By resuming,
Milk/butter contains:
Natural fats (mainly, saturated triglycerides, lipophilic Vitamins (A, D, E, K), cholesterol and other steroids and many other lipophilic metabolites, in addition with absorbed hydrocarbons and their metabolites.
Furthermore, different lipophilic coumpounds might have identical Rt in chromatograms.

[pgk]

So, what you can do, are:
1). Extracting with n-heptane (or n-hexane, or n-penetane), cyclohexane and diethyl ether, followed by GC of the organic extracts.
Theoretically, GC chromatograms are identical but with slightly different quantitative appearance, due to the slightly different partition coefficients in the above solvents.
Indicatively, lipophilic compounds with polar groups hate to be mixed in cyclohexane but prefer diethyl ether.
2). A series of normal phase HPLC experiments, in mixtures of n-hexane/ethyl acetate and cyclohexane/ethyl acetate at various volume ratios, as eluants and using both UV and refractive index detectors. Only, aromatic and unsaturated compounds are detected by UV detector (say, at 254 nm). While, both aromatic and aliphatic compounds can be detected by refractive index detector (but with higher detection limits).
3). A series of reverse HPLC experiments, in (say) acetonitrile/water at various volume ratios, using both UV and refractive index detectors.
4). Matching the chromatograms peaks with the ones of known compounds form the literature, EPA standards, etc.
5). Using more advanced techniques, such as GC/MS and LC/MS, for the chemical structure identification.

[rolnor]

It feels somhow this question is submitted to the wrong forum, this is not a organic chemistry question but a analytical chemistry question and I feel that the answeres given (including my own) is of low quality. You also need to get input from a pharmacokinetik expert.

[pgk]

1). The above described analytical techniques, are effective in distinguishing between remaining traces of monomers and small oligomer impurities in polymers, as well as measuring remaining traces of solvent mixtures in plastic articles made of solvent-born resins at sub-ppm scale.
2). Pharmacokinetics deals with the mathematical modeling of absorption, metabolism and excretion by considering metabolites as given. This is rather an issue of experimental toxicology (to be distinguished from clinical toxicology).

[PeaGreen36]

Thanks guys, you have given me a lot to think about (especially pgk!)

We currently have GC-FID which is used for TPH analysis in soils/waters, GC-MS and HRGC-MS (with a triple quad GC-MS also arriving imminently - yay new toys!). I think the high resolution instrument may be best suited in order to differentiate between very specific ion ratios required to see past the non-target compounds, as isolating them through sample clean-up seems near impossible.