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Topic: Separating the constituents of a glycerol/water solution  (Read 2658 times)

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Offline horse

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Separating the constituents of a glycerol/water solution
« on: February 19, 2017, 02:30:57 PM »
I changed the title of this thread because my original idea turns out to be wrong.

So I want to hone my abilities to extract and isolate various useful compounds and reagents from different sources, and in the future plants are gonna be a big source for me since theres a whole world of interesting and useful compounds contained in plants, most of which we don't even know about yet.

So I'm starting with a simple situation. A solution in which glycerol is the primary solvent. Theres some water in there too, but its viscous so I assume glycerol is the main one.

I want to isolate all the solutes if possible, but I might have to just settle for the easiest ones. So most of the solutes are organic acid salts and acids. Theres one water soluble organic compound in there. And one base salt. So the first thing to do I'm thinking is isolate the base salt first, because with an A/B extraction, thats the only thing that'll make it into the non polar phase.

I'm limited to the solvents that I have, which are a hydrocarbon mixture (C8-C12 I think) and a toluene/xylene mixture. I don't know which to use, but I know that glycerol is pretty insoluble in hydrocarbons, so I need to go with whatever is least likely to cause an emulsion.

So what I'm thinking is heating the solution a little then adding a strong base (NaOH) to the glycerol solution, maybe a little extra water, and keep adding base until the pH is well into the alkaline range. I'll watch to see if anything precipitates out. If precipitate forms, mixture sit in the fridge or freezer for a while to increase precipitation and to let the solids settle to the bottom.

Or maybe a better idea would be to add calcium hydroxide and boil the solution, that way some of the acids might form insoluble calcium salts and precipitate out too.

In either case, then decant as much of the liquid as possible. Then add the non polar layer, and carefully shake carefully to look for signs of emulsion emulsion. If no signs of emulsion, then shake crazy. Then separate the layers, and filter out the insoluble calcium salts (if there are any) and store them for later workup.

Then dry the organic phase with MgSO4 and bubble anhydrous HCl through it to see if precipitate forms. If so, thats a sure sign that the precipitate can only be one thing, the base.

Then the insoluble calcium salts, wash them with water and an acetone and dry them. Acidify with an acid that forms a soluble calcium salt. Then evaporate the water, and do some solubility tests, first acetone, if it dissolves some of the solid mass, then thats a start. Then try ethanol next. Thats about as far as I'd go.

Is there anything I'm missing here, is there a superior method to handle a situation like this? Chromatography is outta the question since I don't have a column.
« Last Edit: February 19, 2017, 05:45:41 PM by horse »

Offline hypervalent_iodine

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Re: Separating the constituents of a glycerol/water solution
« Reply #1 on: February 19, 2017, 07:23:09 PM »
Columns followed by HPLC really are the go-to with these sorts of projects. In terms of extraction from crude material, I think the people in our group that do natural products isolation with plants use MeOH, EtOAc and other organic solvents of that nature. There is plenty of literature out there on that aspect you can look up.

My main question would be (for your long term goals), how are you going to know if you have one compound or 50 in your isolates? How are you going to know what you have? In terms of new compounds, how do you plan on characterising them and solving their structures?

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