First QuEChERS Extraction of Marijuana with GCxGC-TOFMS Analysis, dudes…

My Restek colleagues Julie Kowalski, Michelle Misselwitz, and Amanda Rigdon, along with Professor Frank Dorman from The Pennsylvania State University (PSU), report here what we believe is the first QuEChERS extraction of marijuana, with subsequent analysis using GCxGC-TOFMS.  We were assisted in this task by Randy Hoffman, a Police Officer Specialist/Evidence Technician at PSU, who very kindly donated the samples confiscated from some students who probably should have had their minds on class, not grass.

Our interest in this topic is mainly about medicine, since at least 15 states (Pennsylvania is not one of them) and Washington DC have enacted laws to legalize medical marijuana.   When you fill your prescription, how do you know your remedy is active (potency, or cannabinoid content), pesticide-free, and without bacteria or mold or fungus?  Well, you probably don’t, but eventually FDA might get involved and we’ll need good, robust analytical methods, especially for pesticide analysis.  We think that you might be able to do one extraction for both potency and pesticide determinations and we’re high on QuEChERS, so we went for it.

First, the potency work, or cannabinoids determination.  Although you don’t need GCxGC for the BIG THREE (cannabidiol, Δ9-THC, cannabinol; by the way, Restek has a reference material containing these compounds…), we used it to illustrate one of the benefits of that technique, the structured chromatogram.  In the first figure below, the GCxGC contour plot (or chromatogram), you can see that compound classes position themselves in certain areas.  This helps identification, and makes discovery of new compounds within classes a bit easier (e.g. perhaps there are undiscovered cannabinoids out there with medicinal benefits).  Zooming in, we can see the terpenoid classes, which are thought to have therapeutic effects.  Finally, you can see the cannabinoids, including cannabidiol, one of much interest given that “it has been shown to relieve convulsion, inflammation, anxiety, and nausea, as well as inhibit cancer cell growth” (

We quantified cannabidiol (CBD), Δ9-THC (THC), and cannabinol (CBN) for 4 marijuana samples using QuEChERS and GCxGC-TOFMS and the results are presented in the table below.  Since the samples had been stored in an evidence locker for over a year in some cases, the CBN content is relatively high versus fresh marijuana.  CBN increases as THC degrades.  The THC content is in line with what is typically reported for higher grade illicit marijuana.

Stay tuned for a report on pesticide analysis of marijuana using QuEChERS and GCxGC-TOFMS.  As you might imagine, the extracts are extremely complex, similar to what we saw in our dietary supplements work.

Siezed marijuana for QuEChERS extractions at PSU.

Marijuana for grinding prior to QuEChERS extractions.

Professor Frank Dorman at Penn State University grinds the goods.

Weighing the marijuana into the QuEChERS extraction tubes. It is full of static!

The first QuEChERS extracts of marijuana. They are almost black, and are very complex.

GCxGC-TOFMS contour plot of QuEChERS marijuana extract showing "structured chromatogram", where compound classes elute in certain regions. Rxi-17Sil MS x Rxi-5ms column combination.

Zooming in on the GCxGC terpenoid region for QuEChERS extracts of marijuana.

The cannabinoid region of the GCxGC chromatogram of a QuEChERS extract of marijuana.

Cannibinoid results in percent for samples of marijuana analyzed by QuEChERS and GCxGC-TOFMS.


6 Responses to “First QuEChERS Extraction of Marijuana with GCxGC-TOFMS Analysis, dudes…”

  1. Josh Wurzer says:


    Great work! I have been doing a Quechers extraction of cannabinoids for edible food products as well as a Quechers extraction of cannabis flowers for pesticide residue testing for over a year. Our laboratory tests medical cannabis samples in California. We would love to see restek offer standards for CBG, THCV, CBC, as well as THCA and CBDA (THCA and CBDA are the major cannabinoid constituents of raw cannabis flowers but are degraded into THC and CBD on a GC column).

    I would love to share some data with your group if you are interested.

    Josh Wurzer
    Laboratory Director
    SC Laboratories Inc.

  2. Jack Cochran says:

    Greetings Josh!

    Thanks so much for your kind comments and for letting me know of your use of QuEChERS. I’ll forward your reference materials request to our standards group. I do know they are interested in expanding the line, but some of those neat compounds are SO expensive. I’m just getting ready to post on our pesticide results for the illicit marijuana we extracted. We found numerous pesticides, so the work turned out to be quite interesting. The samples are unbelievably complex, and needed a multidimensional technique, in this case, GCxGC, for the quantitative effort.



  3. Blake Meinert says:

    Hello Jack,

    I have had substantial experience analyzing for chlorinated pesticides in soil and water, but I had not considered their use in marijuana crops. What pesticides did you primarily see? Is there one primary pesticide of choice with growers that you know of? This is interesting.


  4. […] we reported on what we believe is the first application of QuEChERS for marijuana, using it for potency analysis with GCxGC-TOFMS.  Ultimately, the plan was to determine pesticides […]

  5. Jack Cochran says:

    Hi Blake:

    The pesticides we saw on our small sample size were o-phenylphenol, hexachlorobenzene, metalaxyl, chlorothalonil, imazalil, and cypermethrin. Interestingly, all are fungicides except for the insecticide, cypermethrin. Mold/fungus apparently is a big problem for marijuana that is being dried/stored, so maybe this finding isn’t surprising.

    With the small sample size we had, and the fact that all of our samples were illicit marijuana, I’m not sure if there is a “primary pesticide of choice”. At least with the medical marijuana, it may be that bifenazate (Floramite) and abamectin (Avid) are the “pesticides of choice” to control spider mites in indoor grow operations. But since this doesn’t seem to be a well regulated area yet, I’m not sure if we know what to expect as regards pesticide use.


  6. […] cannabis to (1) develop methods for possibly fingerprinting marijuana types, (2) characterize marijuana potency, and (3) analyze for pesticides in marijuana with GCxGC-TOFMS and […]

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