RSA fail

Had a Batch of distillate fail RSA do to residual ethanol. When I pulled my test I made sure not to clean anything with ethanol. So I think I have ethanol in the oil some how post distilling it. My first question is how do you think this would happen? Didn’t let the collection ball sit for long enough? My second question is what’s the best way to get the ethanol out of the oil? I was think about putting it in my load flask and running it till I see a little bit of oil and stopping the run. I would think that if I ran it up to the point of seeing out I would have boiled off any residual ethanol.

Are you using a WF or FFE? Are you putting crude mixed with ethanol into the feed flask?

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we decarb post winterization and roto. I do still see ethanol pull at the beginning of the run. I’m unfamiliar with the terms WF FFE?

What setup you using to distill? Shortpath - Wiped Film - Falling Film Evap.

How do you decarb? If you’re decarbing the oil post rotovap, there shouldn’t be any ethanol. It boils off around 78 C. What temp do you decarb at?

short path. We decarb at 175c on the hot plat and wait till we see the oil rise up 115c and pull it.

As far as I can tell this makes no sense, I’ve never seen distillate fail for ethanol. (Didn’t think it was possible unless you mixed fractions.)

How much terpenes are being added back in? Some terpenes quantify as alcohols in analytical testing and can cause false fails.


this was post distillation so no terms added. When you say mixing fractions you mean like the terp ball with your main body?

Any ethanol will come off before cannabinoids, and before terps. It should azeotrope with any water that was present and come off first, then you switch flasks to get the terps, then switch for the cannabinoids. Unless you mix fractions, it’s not possible (to my knowledge) to have ethanol in your cannabinoids.


I said the same thing. At first I though it was when we pulled the test and I made sure on this one there was no ethanol around. So I’m super confused I’m also wondering if there is trace amounts left in our collection flasks that would cause this. But before using them I make sure I don’t see any drops left in it.

I suppose residuals in the flask is the only thing that makes sense. I always rinse mine with acetone last and blast it with nitrogen to dry it before putting it on a rack.

interesting why acetone?

It cleans terps out really well, which isopropyl doesn’t do so well at, and it dries clean and very quickly.

I should note that I use all lab grade solvents.


me as well I’m going to check with my supplier and see if they have acetone and what the idea of using nitrogen?

Any chance your vacuüm pump vapors get back in your system ?

We recently purchased some distillate that came back for ethanol as well after we mixed in terpenes for vape pens. Curiously the same distillate was used to make 4 batches (flavors, strains, whatever) and only 2 came back with ethanol. We use isopropyl to clean and due to boiling point there is no way. Maybe the testing lab is using it to clean and its not fully drying?

Are you using a single or multiple distribution adapter for your collection flasks? Its unlikely, but ethanol vapors could of collected in all of the receiving flasks if you used the multiple adapter. If you have a vac oven use it to purge the remaining ethanol if there is actually any. Another thing you could do is send a blind test to your lab to make sure they are not screwing up. Don’t tell them its the same sample and see if the results are different. Analytical labs make mistakes too.


I also use acetone if I am not out to clean my glass. I have used every solvent at times for cleaning if handy and without any question acetone is best. It evaporates away so nicely but also just does a better job for me. I use it to clean the cold finger of my sublimator before popping it back in and it is a no brainer there.
there is sticky THC residue and acetone and a kimwipe cut through it faster than other. Iso is my second fave for cleaning if out of acetone but it will tend to leave more of the trace residue behind without more scrubbing.


Why separate terps from water/etho?

It’s what we use for inert gas, plus, it’s about the same price as compressed air. Just using it to quickly dry the glass.

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To add them back into the distillate. The company I work for uses strain specific terpenes pulled in house and remixed back into the oil or distillate.