Total THC vs Delta-9
Understanding THC Potency Reporting
The THC molecule is naturally produced in plants in its inactive form known as THCa.
Only a small fraction of the active delta-9 THC (delta 9-THC) form is generated in the plant.
Heating the inactive THCa results in its conversion to active delta 9-THC.
Only a maximum of 87.7% of the inactive THCa can be converted to active delta 9-THC.
THCa and delta 9-THC Reporting
In addition to reporting THCa values, labs must now calculate the amount of delta 9-THC that can form from THCa
Example of Reporting and Total THC Calculation
The data shown (top right) indicated a THCa content of 24.34% and △9-THC content of 0.74% in the sample.
To determine the maximum △9-THC that can form from THCa, the THCa value must be multiplied by 0.887.
24.34% (THCa) x 0.877 = 21.34% Maximum △9-THC formed from THCs
To get the final “Total THC” value, the maximum △9-THC formed from THCs is added to the value of △9-THC that was present in the sample.
21.34% △9-THC (from THCa calculation) + 0.74% △9-THC (from the plant) = 22.08% “Total THC”.
Delta-9 THC Testing for Hemp under CT Public Act 19-3 August 27, 2019
The lab may dry the sample prior to extraction both to convert THCA to delta-9 THC and provide a dry weight basis for the analysis. The analysis must be done using either of the following methods:
a. Gas chromatography with flame ionization detection (GC-FID), which also converts THCA to THC during analysis. Our analysis produces one test result and it will be total delta-9 THC.
b. High performance liquid chromatography (HPLC) and calculate delta-9 THC separately from THCA using the formula below.
Labs Processing Wet Samples
Labs processing wet samples will need to calculate a dry weight separately and apply that measurement to the test result to convert to dry weight basis.
Labs processing wet samples must use a technique capable of measuring both THCA and delta-9 THC and use the formula (presented on the next slide) to convert THCA to delta-9 THC.
While other metabolites of THC exist, only include THCA in the calculations.
Delta-8 THC is not part of the calculation, only delta-9 THC.
Formula To Use:
Total theoretical tetrahydrocannabinol or THC content is the maximum amount of possible delta-9 tetrahydrocannabinol in a hemp crop if total conversion were to occur and will be determined by the following calculation:
the sum of the concentration of delta-9 tetrahydrocannabinol and its precursor, tetrahydrocannabinol-A, multiplied by 0.8777 on a dry weight basis and reported to two significant figures.
Method of Testing
Labs must indicate the method of testing on the Certificate of Analysis (“COA”). The COA must also include a statement whether or not the sample has a delta-9 THC concentration greater than 0.3% on a dry weight basis.
The reporting limit is defined as 0.3% delta-9THC. This includes a measurement uncertainty determined by the laboratory. As an example, if the measurement uncertainty is 30%, the reporting limit will be 0.39% THC and all samples below 0.39% will be reported as less than 0.3%
a. Results below the reporting limit are reported as less than 0.3% with a result status of “pass”
b. Results above 0.3% will be quantitated and reported with a result status of “fail”
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Wet Samples
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