Taxing marijuana potency – Rose Habib

UPDATE September 22, 2014:  Ms. Habib notes: CBDA is an important standard but wasn’t available commercially. It is now available commercially.


Is THC content is a practical tax base for marijuana concentrates?  I asked Rose Habib.  She was part of the BOTEC team that worked on Washington’s marijuana laws, and is an analytical chemist with Cannabanalysis Laboratories in Montana,

To restate the question, can different labs  measure liquid alcohol extracts and come back with THC results that are very different?

We have a good way to go.  Here’s Ms. Habib’s full answer:

It is true that labs currently could take the same alcohol extract and get different results.  Because of the homogeneity of the sample, we know that this is not because of sample irregularities, we can easily attribute that to lack of analytical accuracy.

In other industries like pharma or supplements or cGMP regulated industries there are validated methods by which a specific test must be conducted.  These methods cover instrumentation, calibration curve, compensating for possible interferences and sample preparation methods.  They must be proven to work through a series of standardized  benchmarks including Precision, Accuracy, Appropriateness, Robustness, Linearity, Range, Repeatability, Detection Limit, Quantitation Limit, and Interlaboratory Reproducibility.
The US Pharmacopeia provides testing standards for many over the counter drugs and herbal supplements.  If a lab follows those methods they can be assured of being well on their way to a true answer.

None of this exists for quantifying cannabinoids.  Each lab has developed their own method, some choosing inappropriate instrumentation.  Many of them are not familiar with industry standards for testing and method validation. Many of them are reproducing and tweaking methods found in published literature.  Some of them know what they are doing and are doing good work, some are happy they’ve figured out how to make a chromatography peak and now consider themselves professional analysts. The unregulated nature of cannabis production, processing and testing have allowed a significant number of amateur analysts to set up shop. This is unfortunate.

In Washington, they have chosen to follow the American Herbal Pharmocopeia’s monograph on Cannabis.  This monograph, which had been in progress as a back burner project, was completed at the urging of the Liquor Control Board with the input of many of the cannabis testing labs currently in operation.  However much LCB requires labs to meet certain standards of accuracy and precision will be directly reflected in the quality of data produced. Spot checking and round robin testing should help illuminate outliers.

Science runs on consensus and reproducibility.  When producing and testing cannabis rise to the normalcy of everyday production, the quality will improve all the way around.

Many of the labs in CA have formed an industry association and regularly participate in round robin testing exercises in order to expose outliers.  No one looks good if results are irregular between labs.

Most of the disgruntled growers, and complaints about testing labs come from amateurs who have sent bud samples to various labs and are upset about the variability of the results.  Unfortunately, the amateurs have no concept of sample homogeneity and usually break a bud down and send it to various labs.  This sort of amateur sleuthing, compounded with righteous indignation and an utter lack of knowledge about QC testing have done the testing industry no favors.

 One last source of irregularity is sourcing chemical standards.  Each cannabinoid quantified must be compared to a known chemical standard.  As recently as two years ago the only cannabinoids available were THC, CBD, and CBN.  Although these are available from at least 3 companies, labs have reported concentration discrepancies between the sources. Slowly Delta 8 THC came out, then THCA, then THCV and CBG became available.  The three initial cannabinoid standards are easily obtained, the others are exorbitantly priced, $300 for 1mg in 1mL of solution. An important cannabinoid not commercially available yet is CBDA. Any lab quantifying CBDA has personally isolated the compound and is using that for a standard; a technically challenging and time consuming process.  Acidic cannabinoids are unstable as it is, and great care must be taken to not allow it to degrade into CBD.

A lab industry regulator who routinely inspects labs and results, and manages round robin testing to ensure interlaboratory consistency would help.


While it’s ‘easier’ to tax concentrates and edibles because they are measurable, I’m not sure we want to tax people for arguably safer behaviors.

Concentrates refers to a number of extract forms.  One of those is simple extracts, commonly used for dabs (but also ingested by patients). They are NOT liquid, but more the consistency of cold molasses or sometimes brittle like toffee, aka “shatter.”

Taxing by THC is only going to be viable once labs are subject to performance certification and/or have a nationally recognized validated method to follow.  The only people with a wealth of cannabis testing are crime labs and they are not interested in quantification, they are only interested in identification.  They are not interested in minor cannabinoids.  The only person who has the facilities and experience to quantify any and all identifiable cannabinoids is El Sohly in Mississippi, and he only works for the government.

 Right now, individual labs’ mere existence rides on their own developed methods for testing cannabis.  That is their IP and there is no personal benefit in sharing.  Any and all of them could be considered valid, however with no external regulatory body, no one knows how they are getting their answers.


Here’s more from Ms. Habib and colleagues: or click here or upload this:  Rose Habib 1c-Testing-for-Psychoactive-Agents-Final.


5 thoughts on “Taxing marijuana potency – Rose Habib”

  1. Ms Habib is right on the money. I have significant experience in both the pharmaceutical and environment laboratory based testing business and can tell you it will be a while before the technical issues are resolved. It took years in the environmental industry to develop the technical sophistication required to not only identify but quantitate well known pollutants.

  2. While it’s ‘easier’ to tax concentrates and edibles because they are measurable, I’m not sure we want to tax people for arguably safer behaviors.

    I don’t know if this comment comes from Ms. Habib or Mr. Oglesby but it’s absurd either way. Edible cannabis is metabolized in a different way that produces the 11-hydroxy-THC metabolite of THC along with acute paranoia. Smoking cannabis, while appearing analogous to cigarette smoking shows none of the associated harms of burning tobacco.

    A facile confusion of (lethal) tobacco smoking and (benign) cannabis smoking should not lead us to favor and incentivize more potent forms of marijuana–especially not merely for ease of measurement of newly-generated revenue!

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