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Methanol Extraction Gone Wrong?

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darkstate

darkstate

Rising Star
A published methanol extraction on 171.2g of mimosa bark was undertaken.

The soxhlet was ran for 5 cycles using 300ml of solvent, which produced a very nice deep purple (no relation to the rock band) liquid. After vacuum distillation, the residue was freebased with with sodium hydroxide and extracted with hexane using a separation funnel.

The extract was washed with pure distilled water twice and washed with pure water with 100mg of sodium carbonate. The two liquids were separated and the non-polar part was left for several several days and freeze precipitated. The expected yield was insignificant. Crystals formed with a familiar scent, but nothing like a traditional STB tek.

However, all the washes were kept for posterity (and of course in case anything went wrong) and an observation of the sodium carbonate wash part after evaporation yielded soda clumps (as expected) and lots of pretty crystalline patterns growing up and on the Erlenmeyer flask at about two thirds the way up.

Question 1: Was there a mistake in washing the freebase?

Question 2: If the sodium carbonate wash actually contained anything of interest, what would be the best way to validate?

Question 3: Slight deviation to save time and effort - would it be possible for the sodium carbonate wash residue to be combined with a sodium hydroxide sludge from another experiment, and then a non-polar extraction to be performed? Would there be any unwanted reactions taking place?

Question 3.1: Would it be possible to combine both wash residues, add HCl proportionally, evaporate, freebase, and extract using a non polar solvent?

Question 4: Should a totally different approach be taken here?
 
benzyme said:
soxhlet is a waste of time.
Click to expand...
I have no experience with Soxhlets but there are quite efficient and less expensive extractors.

I use a simplified extractor with methanol all the time. It takes less than 2 hrs to exhaust completely 50 g of mhrb. If I need to process more I connect 3 extractors to the same boiling flask with an adapter and can extract 150 g withing the same 2 hours.

Where I live such an extractor could be made by a glassblower for $50.

benzyme said:
better time would be spent using a physical method to break open the plant cells, since that's where the alkaloids are.
boiling, pressure cooking, etc.
Click to expand...

I find it very useful for any extraction.

Usually I run a few freeze/thaw cycles with microwave heating in between.
 
Trickster said:
I use a simplified extractor with methanol all the time. It takes less than 2 hrs to exhaust completely 50 g of mhrb. If I need to process more I connect 3 extractors to the same boiling flask with an adapter and can extract 150 g withing the same 2 hours.
Click to expand...

it takes about 40 mins to do the same with a pressure cooker using dilute acid, and you're already a step ahead (acidification); takes less than 20 mins with a sonicator.

of course, if time isn't an issue, use whichever method works for you with the available tools.
 
benzyme said:
it takes about 40 mins to do the same with a pressure cooker using dilute acid, and you're already a step ahead (acidification); takes less than 20 mins with a sonicator.

of course, if time isn't an issue, use whichever method works for you with the available tools.
Click to expand...

I got very much interested by this idea and bought an electric PC to see how efficient it is. It did not impress me at all. It would have been great if there was no need to separate MHRB powder from liquid after each cooking. To do it efficiently takes either more than an hour of vacuum filtering or at least a day of settling and decanting. So it took me 4 days to do 5 cookings.

So, IME, Methanol extraction (~70%) with Soxhlet or similar extractor is much faster and more efficient than PC. The PC method probably would work better with shredded (not powdered MHRB). It would also work great if only one cooking was enough.

P.S. I did not try a sonicator yet, but it seems that the filtration problem would still be there. For efficient extraction the alkaloind-containing plant material still needs to be washed with fresh solvent (acidified water, methanol+water, or whatever) several times.
 
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