Soxhlet Extraction: Defat crude extract or plant material?

[Sertürner]

I am in kind of a pickle. After having asked many many people, I cannot find straight answer to this question.

When obtaining crude extract from plant material, is defatting the plant material before the extraction the better way to go?

Or is obtaining a crude extract first and then stripping lipids and chlorophyll a better option?

I would think that defatting the plant material might produce a higher yeild, I could save the organic solvent for further refining while I use ethanol or something on my defatted plant to obtain cleaner crude extract. But this method would also have me concerned about a long reflux of a highly flammable solvent such as n-hexane.

The other option, obtaining crude extract via soxhlet and ethanol and then defatting that with hexane and a filter seems a bit safer but would result in a very slow process with poorer results.

Any thoughts?

Mr. Deeds

 

[draculic acid69]

What plant r u extracting?

 

[vecktor]

defat ground plant. final answer.
hexane from the defat can be recovered and recycled.
Hexanes and Ethanol are partly miscible, and they fom micelles. separating hexane from ethanol is slow and incomplete

 

[Sertürner]

defat ground plant. final answer.
hexane from the defat can be recovered and recycled.
Hexanes and Ethanol are partly miscible, and they fom micelles. separating hexane from ethanol is slow and incomplete

Thank you for this. That was another issue I was running into, separating the hexane from the ethanol if I was going to defat after extraction. The fact that they are miscible would make using a sep funnel a very tedious process.

So in regards to hexane, I have been reluctant to use it because of the fume potential. It is one of those things where I worry that my workspace doesnt have the greatest ventilation for an organic solvent. In a soxhlet (in theory), I shouldn't have to worry about fumes, but just it still worries me.

 

[vecktor]

Thank you for this. That was another issue I was running into, separating the hexane from the ethanol if I was going to defat after extraction. The fact that they are miscible would make using a sep funnel a very tedious process.

So in regards to hexane, I have been reluctant to use it because of the fume potential. It is one of those things where I worry that my workspace doesnt have the greatest ventilation for an organic solvent. In a soxhlet (in theory), I shouldn't have to worry about fumes, but just it still worries me.

use heptane if possible it is much safer neurologically than hexane and a bit less flammable.

soxhlet shouldn't realease much vapour so long as the condenser is long enough and the flask at the bottom is big enough, bigger is better with a bit of spare solvent because it doesn't throw loads of vapour up when the thimble empties. also boiling stones are essential.

 

[Sertürner]

@vecktor Sounds good. Hadn't thought about heptanen just pet ether and hexane. Both of which come with some risks.

In regards to the soxhlet, I have used it for EtOH extractions with great results. No fumes escaping and using makeshift boiling stones. I have a new mantle with magnetic stirring built in coming soon so I will not need the chips when that comes. The condenser is pretty large about a foot long Grahamn and works like a charm.

Now I have been wondering this as well:
The extraction chamber will hold about 50g of material but I would like to do about 200-250g which will require multiple thimbles.
Is the best way to switch out the thimble just to wait until the solution had cooled and then replace and then reheat? This seems like it might decompose some alkaloids as the BP will be higher every time I have to reheat. Any tricks for switching out material in the chamber?