Ethanol Residual Issues

Hello Forum,
I've been wracking my brain with this question for weeks now and can't seem to find the sweet spot. After winterizing CO2 output in 200 proof ethanol, using a rotary evaporator for ethanol purge/recovery (52C, 27.5" Hg), I cannot get anywhere near some dispensaries 500 PPM residual requirement (practically 100% purge). The state has no standard. Looking at the FDA guidelines for pharmaceuticals, I see they recommend a 5,000 PPM (more a 50mg/day for a 50 kg person) for Class III solvents (ethanol... ). Anyway the lowest residual I've achieved is1500 PPM and that was after extremely heating the oil (not quite decarb) for a long period. Can you feel the frustration? Not sure if it's a bogus standard or if I've just missed some critical step... probably the latter.

So these are a few of my specific questions.

1. Is the 500 PPM figure unrealistic to achieve without killing off all terps and flavor?
2. Some companies apparently are achieving this number... how do they do it? Vac ovens? ambient purging on thin film, adding water at the last part of the purge... hot stirrer plate? I've tried all of these with no success.
3. I've heard that Washington State does not even test for residual with "food grade" ethanol is used as a solvent or in winterization (yes... still a solvent).

Thank you very much for reading this and for any information you can give.

Wow you actually have residual solvent testing done
Nice job your allready doing better and showing more integrity than most people here

I vacuum distill about 20 liters etoh a week.
Stop reading idiot tech on these forums and learn what pharmacist and chemist do. You'll be able to figure it out then
Zubrick is a good read

I was gonna say vacuum too to get higher relative temps without cooking the oil. Did a few of those in labs at tech school in my 30s. I cook my extracts down in my still to recover the solvent then finish them off in a pyrex pie plate sitting on a pot of simmering water with lots of stirring. Wonder what my ppms are.

I'd love to have a rotary evaporator. Getting a magnetic stirrer with heat to do batches of cocobudder on. I have one without heat I use to make colloidal silver in a 1L flat bottom boiling ball.

When I was 17 I dreamed about going to BCIT and taking organic chemistry so I could make acid and other drugs and get filthy freakin rich. When I was 32 I went to help the environment and get a decent job. Got the diploma but no decent jobs came up. Babies at home. Insane wife. Yadda yadda.

Enough of that.

Hope you get it figured out Tako Man.

Maybe fractional distillation under vacuum? Does that exist?

Thanks for taking the time to respond and for the reference. Quick google search says ochem survival manual. I'm guessing that's the one and it's on the way.

Water in rotar evap then evap water in purge oven....use ro water

OldMedUser said:

I was gonna say vacuum too to get higher relative temps without cooking the oil. Did a few of those in labs at tech school in my 30s. I cook my extracts down in my still to recover the solvent then finish them off in a pyrex pie plate sitting on a pot of simmering water with lots of stirring. Wonder what my ppms are.

I'd love to have a rotary evaporator. Getting a magnetic stirrer with heat to do batches of cocobudder on. I have one without heat I use to make colloidal silver in a 1L flat bottom boiling ball.

When I was 17 I dreamed about going to BCIT and taking organic chemistry so I could make acid and other drugs and get filthy freakin rich. When I was 32 I went to help the environment and get a decent job. Got the diploma but no decent jobs came up. Babies at home. Insane wife. Yadda yadda.

Enough of that.

Hope you get it figured out Tako Man.

Maybe fractional distillation under vacuum? Does that exist?

Click to expand...

Fractional distillations must be done under vaccum

Is not placing a column packed with rashig(sp) rings between the pot and still head not fractional distilling? Been 25 years since I got my diploma so fuzzy on some finer points.

Different kind of fractional distillation i belive your thinking of.
Fractioning cannabis oil is actually molecular distillation or molecular sorting or hot vapor distillation aka short path distillation.

Ahhhhh . . . . Thanks.

Has to be under vac to lower thc bp to a cool 245 or something like that

We typically use a Hiedolph rotovape to remove most of the alcohol and finish in a vacuum oven, but here is a procedure developed by Cat Scientific using their stirring hotplate:

How to Purge Ethanol from Cannabis Oil

Using the CAT MCS78 Hotplate Stirrer


Note: This process works for both winterized product and for an Ethanol extraction.

In the following example, total volume of Ethanol-cannabis oil, 400ml.

The first step in the process of purging Ethanol from cannabis oil is to remove the bulk of Ethanol from the solution. This could take some time depending on volume.

1. Set the Probe Temp on the CAT MCS78 to 125°C., and the Plate Temp to 225°C or higher if the volume you’re working with is greater than 500ml.

2. Set the Motor Speed between 60 to 70 rpm’s or higher depending on solution viscosity.

3. While the boiling point of Ethanol is 79.4°C, the Probe Temp is set at 125°C, otherwise if set at 79.4°C, (Ethanol boiling point) the MCS78 would automatically adjust the hotplate, the solution temperature-Probe Temp would reach 79.4°C slowly, so as not to overshoot set Probe Temp, and you’d have a weak boil, rather than a roiling boil, which is optimal for this process.

4. The Probe Temp-solution temp will not surpass 79.4°C, depending on atmospheric conditions until most of the Ethanol has evaporated off. When the solution temperature- Probe Temp reaches 85°C, set the Probe Temp to 50°C. You don’t have to reset the Plate Temp; it automatically adjusts after you set the Probe Temp.

5. Once the solution temperature- Probe Temp reaches 50°C, add 10 drops of distilled water for every 20mls of oil mixture. Process the solution for an hour.

6. After the solution has processed for an hour, set the Probe Temp to 125°C. When the solution temp-Probe Temp passes 90°C, some decarboxylation and water evaporation start to occur; the solution will begin to bubble as the Probe Temp-solution temp rises. The small bubbles form as C02 is boiled off the THC-A. This is an indication of decarboxylation.

7. When the decarboxylation process has been completed, all bubbling stops, set the Probe Temp to 55°C, and process for 48 hours. After processing there should be only trace elements of Ethanol, 54-32ppm. We winterized two batches of C02 extractions for this experiment, one with 200 proof Ethanol and the other, 190 proof. Both yielded approx. 150 grams of absolute. Residual Solvent Analysis, 200 proof. Residual Solvent Analysis, 190 proof.

Disclaimer- Assumption of Risk:

Using the CAT MCS78 Hotplate Stirrer to purge residual Ethanol from cannabis extract or an Ethanol extraction carries inherent risks that cannot be eliminated regardless of the care taken to avoid such risks. The specific risks include, but are not limited to: minor bodily injury, major bodily injury; death; loss of or damage to property. You understand and appreciate the risks inherent in this process, including but not limited to those set forth herein, and you hereby assert and agree that operating the CAT MCS78 Hotplate Stirrer for this process is voluntary and that you knowingly assume all such risks.