NIDA/PHS Review of MAPS’ Vaporizer Protocol:
This is to inform you that a committee of scientists at the U.S. Department of Health and Human Services has reviewed the Chemic Laboratories proposal to evaluate various aspects of the Volcano Vaporizer. The committee had some questions and issues for clarification on the proposal that are detailed below.
THCA: the definition of THCA is not clear. Do the authors refer to the precursor to THC in plants that produce THC upon heating, or to 11-nor-∆9-9-carboxy-THC, the metabolic product of THC? The authors state that the concentration of this compound will be determined, but the source of THCA is not provided, and no further information on its detection, quantification, or results are provided? In addition, the physiochemical characteristics of this compound are quite different from the other cannabinoids and an appropriate internal standard should be included for quantification. It is quite possible that THCA in Cannabis Sativa products could differentially contribute to the amount of measurable THC in the three methods of analysis- Soxhlet extraction, vaporization and combustion. It is not known whether the THCA will decarboxylate at vaporization temperatures or whether it might decarboxylate during Soxhlet extraction (doubtful). This could introduce variability into the results. Has the THCA content been determined prior to testing? In general, NIDA does determine the THCA content of its cannabis batches. This assumes THCA refers to the precursor acids.
Why would external standardization be necessary? Internal standardization is the preferred method of analysis. Would it not be feasible to fortify the Cannabis sativa plant material with internal standard rather than fortifying the methanolic solutions to account for losses during heating, absorption on the volcano parts or during combustion? Why is only one deuterated cannabinoid used as an internal standard? The committee believes that deuterated CBD and perhaps deuterated CBN may be available to improve quantification of these analytes.
Why is LCMS rather than LCMSMS utilized for identification of the cannabinoids? Why is only TIC used rather than single ion monitoring? How many ions are monitored for each cannabinoid (minimum three with two ion ratios gold standard analysis) and two minimum for each internal standard (one ion ratio)? Please submit the method validation criteria for the LCMS method showing sensitivity, specificity, accuracy or bias, imprecision, matrix effect evaluation, recovery (if performed), interferences, linearity, carryover evaluation and/or other criteria.
What is known about pyrolytic conversion of the target cannabinoids by the volcano vaporizer and the combustion method?
Page 4 Tetrahydrocannabinol, cannabinol, cannabidiol and Tetrahydrocannabinol-acid are misspelled.
Throughout the protocol data are used in the singular, data are always plural.
P 7 Why is the weight of the glass filter included in the total weight of the marijuana? Has potential absorption of cannabinoids to the balloon, reservoir or other parts of the volcano been determined?
P10 Acetonitrile is misspelled.
P10 evaluation criteria are inadequate.
What are retention time criteria?
What are appropriate chromatography criteria including peak shape, peak resolution, S/N?
What criteria are in place for variability between the four calibrator injections within a single run?
How many samples are included in each batch with the four calibration curves?
Are the concentrations of each calibrator individually determined against the entire curve? What is the acceptable concentration range? Are there procedures for eliminating specific calibrators if they do not meet the criteria? How many calibrators can be dropped from the curve?
Is there drift across a single batch with such a long run time (60 min)? Are calibrators prepared at the same time as samples?
Where are quality control samples? Are quality controls (preferably 3 across the linear dynamic range of the curve) prepared independently and assessed at the beginning and end of the batch or more frequently?
How were matrix effects evaluated? How were other endogenous compounds within the Cannabis sativa evaluated to assure lack of interference? Especially from other natural cannabinoids? Were cannabigerol, cannabichromene for example, evaluated for interference with target compounds?
Although the compounds of interest appear to be present at concentrations well above the lower limit of linearity, what was the limit of quantification? Or was the lowest calibrator used for this purpose?
P11 Reference for Marijuana and Medicine was not included.
Was the valve, mouthpiece and/or filling chamber changed between samples? Is it changed routinely between subjects?
P 25 The common oven bag that is referenced is used for what application? Moisture content only or for delivery of cannabinoids.
Why are no data presented for THCA with the other analytes?
P32 the protocol indicates that all peaks with an area greater than the lowest calibrator area will be quantified, but it appears that uncalibrated peaks are not collected according to the instrument set up? Also, why is the origin included in the linearity? It is a bad practice to force the calibration line through the origin. However, the data did not appear to go through zero? What was done and what is the justification for this choice?
What is the internal standard for the PNA analysis? Was internal or external standardization used? Why not internal standardization if it was not the method used?
P 40 Why was the fragmentor ramp disabled? Why were multiple ions not monitored and ion ratios determined to specifically identify compounds?
Responses/clarifications should be sent via email to me at: Anand.Parekh@hhs.gov. Please do not hesitate to contact me if you have any questions.
Anand K. Parekh, MD MPH
Office of Public Health & Science
U.S. Department of Health & Human Services
The psilocybin/mystical experience study was primarily funded by the Council on Spiritual Practices. Bob Jesse, founder of the Council on Spiritual Practices, has recently sent out a fundraising letter seeking support for further research in healthy volunteers.