Rotovap uses

zanog · Jun 4, 2019

I understand the concept of the rotovap(I have learned a lot this past week, at least it feels that way), a Friderich condenser on a spinning bottle over a heating bath under vacuum(may be a bump guard in between). I got that it is used for gentle recovery and removal of solvents. So, questions...

1, Can it be used for other fractional distillation? Separating THC and CBD from extracts?

2, Can the receiver swapped with a peristaltic pump, would make taking fractions a lot easier? Also could be fed by another pump under vacuum. I guess many people had the same idea before, have you tried? What hose worked best?

3, What would happen if I put dry ground material in this above mentioned rotovap and fed hexane thru the pump, so like a combo solution(continuous extraction and separation, heating and cooling the boiling flask by a program), just brainstorming. Can be automatized easily if it works, I can do it. I know this wouldn't scale up well economically, but for my home use it would be perfect. Would it work?

4, What rotovap I should get? At reasonable price?

5, How do they crystallize THC-A in them?

6, What else one can use a rotovap for?

Future4200 · Jun 4, 2019

1. No

2. Yes and yes, although drawing into the roto with the vacuum pump is simple enough so really only a pump drawing out of the collection vessel would be helpful, and even then, that pump would be feeding another holding tank so you might as well just use a vacuum slurp tank to draw out of the collection flask. Also, the only fraction you collect is your solvent, there's nothing to separate.

3. You would have a big mess. I would strongly advise not filling up your roto flask with plant material. It's a tool optimized for distillation, not extraction.

4. TouchScience (Chinese) as well as Across International (Sourced from China) supply cheap, relatively good rotos. Heidolph is the best, but definitely not reasonably priced.

5. They typically don't. However I did get THCa to crystallize in one after performing a THCa-salt LLE purification experiment. The issue being that typically the solution is not pure enough, ethanol is a poor solvent for crystallization of THCa, and the rapid evaporation of solvents in a roto is jot conducive to crystallization.

6. You can put box wine in it and distill a relatively nice brandy. On IG there's a profile called "Flavorvap" and it's all about chefs that use their roto for culinary endeavours. Super neat stuff

zanog · Jun 5, 2019

Thank You Future4200! Your answers were really helpful and exactly what I asked, I wish I would get answers like this always. For me many times the most useful thing is to rule out possibilities quickly. Well this thread served it's purpose quickly, thanks again!

zanog · Jun 8, 2019

I'm sorry, but this still puzzles me:

1: I'll have a separate short path setup but I was still thinking about this a lot: What is the reason I can't use a rotovap as a fractional short path? Why wouldn't cannabinoids reach the condenser?

2: I can't find anything if I google: vacuum slurp tank, what's another name for it?

6: Can I dry buds in a rotovap without the heating bath? With really low pressure?

Another question so if I can make brandy, this should mean the solvent recovered won't be clean, right? Recovering wouldn't mean almost pure ethanol? which wouldn't be drinkable but brandy is. So me seems logical to take fractions while rotovaping to recover cleaner solvents(keep steady vacuum and raising temp slowly and use a cow receiver or peristaltic pump etc), what I'm not getting here?

Future4200 · Jun 9, 2019

1. A roto doesn't hold deep vac due to the rotary seal + the path from the boiling flask to the condenser is far too long, both of those combined mean you would have to cook the shit out of your extract to get it to boil over. That's not good for your target active compounds

2. Search F42k for it. Basically a separate vessel you pull vac on and use to draw solution from one place to another.

6. You could... Idk why you would though.

You will get two fractions from a roto with ethanol and your extract. One will be all the heavy compounds that didn't form an azeotrope with the ethanol (cannabinoids, pigments, heavy terps, etc), they stay in the BF. The other will be all the light compounds including the ethanol and all of the terps that formed an azeotrope with the ethanol and distilled over

zanog · Jun 9, 2019

Thanks.

1, Got it.
6, I was thinking of really low pressure, non deep vacuum will not be that beneficial, I think.
So that means after solvent recovery I still need to clean up the solvents in an SPD taking it as a fraction to use it again?

Future4200 · Jun 9, 2019

You will have a very difficult time separating terps from ethanol in my experience. Plus, it's not really necessary, for quite a few cycles at least. More of an issue is the water the ethanol likes to grab. Remediating that is not as simple as spd either

zanog · Jun 9, 2019

Future4200 said:
You will have a very difficult time separating terps from ethanol in my experience. Plus, it's not really necessary, for quite a few cycles at least. More of an issue is the water the ethanol likes to grab. Remediating that is not as simple as spd either

How do you know when to dispose of it? Heptane would be the same in this matter, right?

Future4200 · Jun 9, 2019

When your extraction efficiency begins to suffer, or when your ethanol water content gets past 5-10% measured with a hygrometer

zanog · Jun 9, 2019

What about heptane?
So its useful to measure water content after solvent recovery and label the container. How much efficiency you lose by having lets say like more than 5% of water? Is there a graph in existence? no luck with google...

G.O. Joe · Jun 9, 2019

All your questions have pretty much been asked and answered here before. You should know water is insoluble in heptane and THC is insoluble in water. It's unwise to use an expensive piece of equipment to do something done better by something cheaper.

Future4200 said:
You will have a very difficult time separating terps from ethanol in my experience. Plus, it's not really necessary, for quite a few cycles at least. More of an issue is the water the ethanol likes to grab. Remediating that is not as simple as spd either

Chromatography and CaO should fix that.

zanog · Jun 9, 2019

G.O. Joe said:
All your questions have pretty much been asked and answered here before. You should know water is insoluble in heptane and THC is insoluble in water. It's unwise to use an expensive piece of equipment to do something done better by something cheaper.

Chromatography and CaO should fix that.

Yeah, the mixup was caused by my brandy example at the begining, I wasn't planning on using ethanol for anything actually. Heptane needs to be cleaned somehow after recovery, right?

What do you mean by unwise, which use?

G.O. Joe · Jun 9, 2019

There are accessories for rotavaps, you'll have to look in to those, and the temperature and vacuum specs. They do one job really. You should use ethanol, for winterizing. If you run brandy through a rotavap I think a lot will not change except the color. Chromatography wins again for cleansing heptane of things you don't want - alumina maybe? I know just distilling doesn't help petroleum ether much.

zanog · Jun 9, 2019

if my process would be:
dry
grind
extract with heptane
rotovap
decarb
spd
...
OR
dry
grind
decarb
extract with heptane
rotovap
spd
...

where would I insert winterization? Which decarb place is ideal?

And let's leave the brandy example, I could do that with a pressure cooker and some copper piping and other basic stuff, but I don't drink anymore anyway.

G.O. Joe · Jun 9, 2019

Heating pot funkifies it so I'd prefer not to, no matter what the subcritical CO2 patents say. Maybe you know there are patents that go the other way and take advantage of the acid function to isolate the THC as THCA. I'd rather not dry either if I'm using heptane and maybe a little polar additive. Distilling off the heptane at atmospheric pressure would probably do significant decarb? Has anyone compared the speed of vacuum distilling heptane in a 3 liter 45/50 RBF on a heating mantle to using a 24/40 flask on a rotavap? Maybe they aren't necessary at all. What about a 3-neck with each neck having its own condenser, receiver, and vacuum?

zanog · Jun 9, 2019

So I should extract fresh cut weed with heptane and ethanol in a soxhlet for example?

G.O. Joe said:
What about a 3-neck with each neck having its own condenser, receiver, and vacuum?

You lost me here... for what? To be faster than a rotovap?

G.O. Joe · Jun 10, 2019

This is what I'm asking. It's cheaper and more useful than a rotavap. If you Soxhlet heptane and ethanol what I'm guessing will happen is the extractions will be rich in ethanol and the boiling flask will have a sad dark green color. What I was thinking of since I can buy it everywhere is starting fluid. After distilling it. So the more polar part is ether, in a room temp soak with magnetic or overhead stirring.

zanog · Jun 10, 2019

G.O. Joe said:
This is what I'm asking. It's cheaper and more useful than a rotavap. If you Soxhlet heptane and ethanol what I'm guessing will happen is the extractions will be rich in ethanol and the boiling flask will have a sad dark green color. What I was thinking of since I can buy it everywhere is starting fluid. After distilling it. So the more polar part is ether, in a room temp soak with magnetic or overhead stirring.

Okay, so I want to extract only cannabionoids, so I don't need a polar solvent, right?

You got me confused somewhat, please help me understand: If I make a short path setup, from 1 boiling flask with 3 heads with a magnetic stirrer and 3 separate condensers and its on the same split vacuum and collects to the same flask, would be cheaper and more effective than a rotovap. So there is no need to buy one at all? Is this what you meant?

What do you mean by "maybe a little polar additive"? this made me write ethanol next to heptane in the first place.

zanog · Jun 10, 2019

2: What about this? It can be automatized easily, cheaply, and quickly I think. If you don't want air to rush thru the solvent into the vacuum, the second one can match exact inside vacuum or match 1atm when needed: airlock. Oh, and there could be a moving mechanism for collection flasks underneath.

G.O. Joe · Jun 11, 2019

By polar I mean an overall subtle polarity. Alcohols I think would be more likely to be absorbed by the wet or dry plant matter, along with the acetic acid that has been recommended for making sure THCA is in the free acid form? Extraction power is supposed to go down with increasing chain length so maybe heptane could use a little boost? And all of my heptane (and ether) comes from starting fluid. I have not done the experiment to test the rate of distillation from a 3 neck flask, but I have had a Buchi for many years and more often than not am instead satisfied with simple distillation without vacuum or stirring and just one neck.

Rotovap uses

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