Issue with Paclobutrazol (PBZ) Contamination in THC Processing

We’re a manufacturer struggling with repeated PBZ contamination issues and looking for some insights. This issue has lasted a few months now so I’m going to try to hit just the bullet points, but please let me know what questions you have!


  1. Optional Terpene extraction with CO2 extractor. > Store Terpenes

  2. Butane Extraction

  3. Dissolve in EtOH

  4. Cryofreeze.

  5. Filter using Buchner Funnel & Filter Flasks.

  6. Recover EtOH via 20L AI RotoVap.

  7. Decarb in 2L AI SPD.

  8. Pass through SPD once or twice.

  9. Test with a 3rd Party Lab.

We process with both CO2 and hydrocarbon extraction, occasionally using both for the same material batch.


  • Received biomass from a local cultivator, tested and approved.

  • After processing half the material, we had distillate fail for PBZ at 0.8 ppm (Typical LOQ is about 0.009 ppm)

  • R&D tests on related materials showed no contamination. Tested CO2 terpenes extracted previously, although not all batches were identical to failed material, BHO crude (processed after failing lot), and unprocessed biomass.

  • Another batch of distillate tested even higher for PBZ at 1 ppm.

  • Post-failure, equipment and solvents were cleaned. New tests still showed failures.

  • On-site lab sampling showed very small traces of PBZ on all equipment, but no significant source. Additionally, exterior soil samples were taken and PBZ not detected.

  • Following advice from a PBZ manufacturer, all rubber/plastic that came in contact with oil was replaced.

  • Success was achieved with 8 consecutive lots of distillate passing after replacing all plastics and only running CO2 extractor.

  • Needed throughput of hydrocarbon extractor so did a small test run and tested crude, prior to post processing. Crude came back ND, was released into post production line.

  • Distillate which came from hydrocarbon extraction saw further failures with levels just slightly above the LOQ.

Key Points:

  1. Even after multiple solvent dumps and equipment cleanings, the issue persists.

  2. BHO crude tests clean but post-distillation, we’re observing failures.

  3. Replacements of all rubber/plastic parts saw an initial improvement, but the issue returned.

Given our limitations in replacing the entire equipment setup, we’re looking for advice. Specifically, why does BHO crude test clean, but later stages fails? Any guidance on resolving this PBZ contamination issue would be immensely appreciated. Thank you so much for your time!


did you figure out what product had it? I know lots of flower boosters have used it in the past but am wondering if it was labelled or just on some nutes. Its the standard look of buds in many markets.

Unfortunately we haven’t. We don’t grow on site and don’t have any pesticides or PGRs in the building. Even though it passed pesticide testing before we bought it, I believe that it came from the flower. Unfortunately I don’t have any material left from the original lot that failed.

Hydrocarbon will extract and concentrate it. Thats why it was ND flower and failing at processing.


with this system is bs if he bought it legally and cant sell it back when concentrated. I thought there was a powder mix to clean this off the product? mag sil pr?

Yes, but for the material to test ND (>0.009 ppm) then our extract to hit ~1 ppm, we would have had to concentrate it by more than hundred times. I’m under the assumption that we should have only been able to concentrate it by 5-10x. Is that your experience?

I think we’re going to do that, but only once we’ve addressed the underlying source of contamination :slight_smile:

Imo powders can concentrate it even further by removing other stuff. The polarity properties of it are really similar THC so it travels across powders at about the same speed or faster, which is why you may see it spike like that.


I am curious of the method of analysis that is being used to detect the Paclobutrazol? Is it GC-MS?

I believe they use LCMS

DM me an email address …I think I might have a suggestion about how to get rid of it.


@moronnabis a lab I work with is also experiencing PBZ in their distillate. We did identify the material and got rid of all solvent used to extract the material that had it. But working on a way to remediate what we have left. Any insight would be greatly appreciated!

If anyone has pesticide contaminated oil that they can send in a legal hemp derived oil, I will run it with a certain membrane and see nanofiltration is feasible. I have successfully remediated 3/4 of pesticides this method has been attempted on and am always looking for more data. Pyrethrins, Trifloxystrobin, Piperonyl Butoxide, Malathion, and Fludioxonil are all proven at this point.