Extraction of High Acid Solution

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

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I am attempting to do a volatile component characterization from an unwanted sediment material falling out of a beverage product. The only way I have found to dissolve the material in question into solution is via the use of concentrated HCl (tried ethanol, pentane, pyridine, water) - from there my idea was to do a pentane extraction and then inject into the GC which currently has an OV1 column.

However - I do have a recollection of a similar type of sample prep which resulted in substantial column bleed after the fact, presumably due to the high acid concentrations involved that made its way into the pentane. I do not wish to repeat that result and risk damage to my new column.

I am considering adding base after solubilizing the material to gain a less acidic solution prior to solvent extraction - and hoping that it does not cause the re-precipitation of the material.

Thought I would see if there are alternate ideas out there before proceeding.
Why not just extract the sediment with pentane ?

Peter Apps
You could do a "back-extraction". After extracting the acid phase with pentane, remove the acid phase and extract pentane with water to remove residual acid. You could repeat that if necessary.
I am with Peter. Aren't you concerned that you might be creating/synthesizing something when you expose the sediment to the strong acid?

If all you want is the volatile part of the sediment, a couple of extractions with a solvent that is good for your analytes should do the trick.
Peter Apps wrote:
Why not just extract the sediment with pentane ?


Actually I think I will do just that. It very well might get me the answers I seek. If for some reason I need to dissolve as I originally thought was necessary, rndirk's suggestion looks promising as well.

Thanks for all of the suggestions.
I am attempting to do a volatile component characterization from an unwanted sediment material falling out of a beverage product.

I am concerned that we may be trying to answer a wrong question about injecting a solvent extraction of an acidic solution.

It may seem obvious but I presume that your real problem is what is the nature and cause of the sediment? If so GC may not be the way

Just to take a step back and go back to basics.
What is the colour of the sediment after rinsing.?
What are the ingredients of the beverage - could any interact to form a salt.?
Is it happening in many containers of this beverage or just one?
Dissolution in conc acid may be a clue
Is it magnetic?

If it were, for example, the calcium salt of an organic acid then OV1 would be the wrong phase to use

Thank you Ralph

Actually ICP might be an option with regard to the salt angle and with acid solubility being in play it leans in to our sample prep on that instrument. I'm still going to run the pentane extract but this tangent you have brought up is a good one and will be pursued if I don't get some clear answers from the GC.
It would be interesting to hear how you get on.

Since the sediment appears to be beverage and water insoluble, can you isolate enough to try FTIR, ICP, elemental analysis, electron microscopy, etc. ?

Our consumer products were only topical, and stuff like mixing of a different fragrance, viscosity, etc. all got through QA and got released. But anything visually apparent - like your sediment - brought on WW3 ! Those issues had to be solved, and quickly !

One skin product was not a very robust formulation, and repeatedly had issues with methyl paraben precipitation. So that became "fun" to use different techniques each time the situation repeated itself; I remember using HPLC, GC, GCMS, FTIR at least once each to confirm paraben precipitate identity.
I agree with CPG, elemental analysis may be a way forward

Since the sediment is already available in HCl solution then a simple colour flame test in a Bunsen burner may give a clue. Too simple??? :-) :lol:


Since it is an edible product then we can rule out some preservative interactions like parabens or EDTA . For this type of product these would be more like BHT, Na benzoate and sulphites ( blue flame)

If it is a commercial product then Gizmo should be able to give the equivalent of the INCI list of ingredients without betraying confidentiality

At the end of the day, without knowing the ingredients of the beverage and more information then we will be always second guessing.

Depending what the beverage is, a sediment is quite likely to be microbial - either yeast that didn't get filtered out, or something that is growing in there post production. Put some under a microscope.

Peter Apps
If it is an alcoholic beverage then yeast, other microorganism or silica are possible candidates.

Even a low power optical observation (x10), e.g. crystalline or flocculent would be helpful

If a non alcoholic beverage then microorganism contamination can manifest itself by excess pressure from CO2, production of ethanol, acetic acid (change in pH?) or malodour or taste .

An interesting query but , to repeat, without more information we will forever be speculating and second guessing

Lots of good puzzle solvers here. OK, well I had a mishap with the last isolation and I'm working on another right now. The suspicion is that this is a caramel color issue. The wrong choice of product can cause what we see here and, well, its brown.

I've been asked to see if I can prove it or at least provide some additional evidence and my idea is to go initially with a straight pentane extraction and see if I get notable levels of chemical markers that are prominent in CC. I know that normally this might be indicative of natural maillard activity if some sugar got caught up in a heat exchanger too long but in this case the product utilizes artificial sweeteners rather than glucose, sucrose, or any of their close relatives for sweetening purposes so maybe this will provide some useful information.

We'll see. If I get zip from this I will look into exploring some of the other items discussed.
If you are worried about acidic pentane damaging the column, then take the pentane from the acid extraction and wash it with a sodium bicarb solution. This is what is done in the haloaceticacid extraction for drinking waters after acid derivatization. The organic layer is removed and then shaken with an excess of bicarb solution to remove any residual sulfuric acid that might be present.
The past is there to guide us into the future, not to dwell in.
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