Where are these solvents coming from?

I was hoping you guys could offer some insight.

I just got the residual solvent results back on my crude. The first batch I tested came back with no residual sovents save for a .42ppm Ethanol result which was expected. This most recent batch came back with a whole host of new solvents and I have no idea where they came from. I am using Ethanol from the same supplier and nothing has changed in my process. I am freaking out a bit. Did a dab of vacuum grease get in to my roto flask? Did I drop some plastic shavings in the tincture? Did some Iso propyl residue get into one of my beakers? Did I get a bad batch of Ethanol? Mostly I was hoping someone could offer some info on common sources of these solvents:

Isopropanol (I obviously know where this can come from)

Ask your supplier for a CoA.

Benzene, Toluene and others can exist in small amounts in bulk ethanol—its just a result of the manufacturing process to make the ethanol.

Is it 190proof or 200proof? Is it food grade? Is it USP grade?


It’s USP grade Ethanol and it’s from the same supplier as the first batch which registered none of the solvents except ethanol. I’m below recommended limits on most of them but not on Benzene and Acetonitrile.

1 Like

Also, I have the COA for the ethanol. It’s clean.

The next step is to make sure the results you received are accurate by sending a sample to another lab.

If the results are confirmatory you need to assess your process—is there any step in your process that could potentially introduce contamination?

How often do you clean?

How often do you replace elastomeric components (gaskets)?

Do the gaskets have CoAs? (If not find you a RubberFab distributor, they always send certs with the gaskets).

What chilling fluids are you using?

Have you tested the biomass for residual solvents?

My thinking is that (depending on the type of product) you are Recieving a false positive. It happens.


If you haven’t tested the new ethanol that may very well be it. Even if the supplier had clean ethanol last time, given the shortage, now would be the #1 time you’d see them stumble upon a bad batch assuming they may have sourced through a different producer.

Definitely get a second lab to compare. Always a good idea.

Benzene can come from pretty much anything so that one might be hard to narrow down assuming it didn’t also originate in your ethanol.

Hire any new lab techs lately? Lol maybe they don’t know what to clean your gear with.


I’m with @stoopkid sourcing ethanol just got harder. so someone may have messed up and mixed up their denatured formulas (or holding tanks).

everything except the acetonitrile has been used as a denaturant in ethanol.

the best explanation I can come up with for acetonitrile would be that it wasn’t your sample you got results for.


Terpenes can give false positives for solvents including aromatic hydrocarbons. Some of the listed stuff is used to “dirty” ethanol in order to make it industrial/denatured. Acetonitrile can be from the testing lab as it can be used in HPLC.

Was the conteiner for the alcohol new and sealed? If not then maybe denatured alcohol was stored in it beforehand?


On solvents: The company the provides my solvents is pretty highly regarded industrial supplier, so all containers are sealed and definitely new. I am sending things out on Monday for a second test. I know the Biomass is clean as I have followed it from planting to harvest and drying. It has not been tested though for solvents, but I can’t imagine where they would have come from. I clean my primary equipment once a week. My gaskets are all PTFE and Tuff-Steel. SO i doubt anything is coming from there. Chilling fluid in the rotovap is PG/ Distilled water.

1 Like

My thoughts on acetonitrile would be the lab as well, seeing as how it’s a very common mobile phase solvent and not common in cannabis processing at all. However, what I cant picture is how it would pop in his residual solvent panel?

1 Like

Most likely from store bought running alcohol - any type of iso that is watered down and not for human consumption contains those exact chemicals.

That’s why it’s better to use Acetone to clean glassware. Especially now. I can get pure Acetone for about $2 a litre comparing to 8-10 for industrial Iso. Damn corona…

No store bought rubbing alcohol in my lab. Only 99%iso from chem supply company.

Where did you get it from. Usually these are from watered down solvents…

wouldn’t that result in water in ones solvent…

at ~$150/gal who is going to deliberately add acetonitrile to their ethanol to reduce the cost?

if that’s not a lab error, then it’s a really poor job of recycling used HPLC solvent.


The truth is, if it’s 1/3 the cost then tons of unscrupulous sellers will order it like that.

Mystery solved. Best possible outcome: Bad testing. Heart attack averted.