Some results with the internal standard method
Sampling error - twenty portions, each weighing 900 mg., were taken from a lot of carefully mixed "manicured" marihuana.2 The coefficient of variation, due to sampling, for the tetrahydrocannabinol content, was found to be 2.8 per cent. At the 2 per cent tetrahydrocannabinol level this would amount to an uncertainty (95 per cent probability) due to sampling of ±0.11 per cent tetrahydrocanabinol.
This uncertainty could, of course, be reduced by using larger sample weights. A 10 gramme sample, run 4 times, would have an uncertainty of ±0.04 per cent tetrahydrocannabinol (95 per cent probability) at the 2 per cent tetrahydrocannabinnol level.
Deterioration of marihuana with time and temperature.
Three samples of marihuana were kept at room temperature (approximately 24 °C), for a month and analysed for their tetrahydrocannabinol content at the beginning and end of the month. The results were as follows in per cent tetrahydrocannabinol:
Beginning of Month End of Month Difference
Sample A
2.41 2.29
-0.12
Sample B
2.07 1.99
-0.08
Sample C
2.20 2.14
- 0.06
All the differences are highly significant statistically (over 99 per cent probability).
A sample of Colombian marihuana which had been kept at room temperature since its seizure 61 months ago was analysed with the following results:
per cent
Cannabidiol
0.31
Δ1-trans-tetrahydrocannabinol
0.12
Δ6-trans-tetrahydrocannabinol
0.04
Cannabinol
2.03
2
"Manicured" marihuana is marihuana from which stalks and seeds have been removed by passing through a sieve. Crude marihuana, including stalks and seeds, has about a 35 per cent yield of "manicured" marihuana. Crude marihuana from which the stalks have been removed has about a 65 per cent yield of "manicured" marihuana.
No quantitative analysis was available of the original marihuana, but a qualitative gas chromatographic curve existed which indicated a large Δ 1-trans-tetra- hydrocannabinol peak and a small cannabinol peak. The qualitative curve resembled current fresh seizures of marihuana, and one could fairly conclude that in the five year period practically all the Δ 1-tetrahydrocannabinol had been converted to cannabinol. If so, and if an average original tetrahydrocannabinol content was assumed from the appearance of the original curve and the current cannabinol content, a conversion rate of approximately 5 per cent a month would be indicated. This is in rough agreement with the loss in tetrahydrocannabinol content (3 to 5 per cent) found above for marihuana which had stood one month at room temperature. 3
The conversion of tetrahydrocannabinol to cannibinol is in accordance with the hypothesis of Todd ([8] -[9] ) and Adams [(10)] that dehydrogenation takes place biogenically and Levine's observation[ (11)] that old hashish has low tetrahydrocannabinol and high cannabinol content.
A sample of marihuana which contained 2.32 per cent tetrahydrocannabinol and 0.17 per cent cannabinol was held at 100 °C for one month. At the end of that time no tetrahydrocannabinol could be detected and the cannabinol content had increased slightly, to 0.40 per cent. Obviously, at this temperature, there are other mechanisms at work than the simple quantitative dehydrogenation of tetrahydrocannabinol to cannabinol.
(3)Correlation of tetrahydrocannabinol content of marihuana and pharmacological activity.
One important recent development that has demonstrated the need for a precise tetrahydrocannabinol assay is Dr. Harris Isbell's observation [(12)] that response to tetrahydrocannabinol is statistically reproducible if the same subjects are used under the same conditions. Dr. Isbell's work was done with pure tetrahydrocannabinol. He found that 25 µg./kg. when smoked, was a threshold dose; for a 70 kg. man this would be equivalent to 1.8 mg. of tetrahydrocannabinol. A usual dose was about 5 mg., while a dose of 15 mg. produced depersonalization and hallucinations.
If these amounts are translated into a "normal" marihuana cigarette weighing 325 mg., it would appear that a tetrahydrocannabinol content of 0.5 per cent would be at the threshold level; 1.5 per cent tetrahydrocannabinol would produce the "usual" marihuana symptoms; and a 4.6 per cent tetrahydrocannabinol content would correspond to a mind-rocking depersonalization.
3
Dr. Olav J. Braenden of the United Nations Laboratory has informed me that to avoid deterioration, the United Nations reference samples of marihuana are kept under nitrogen, at freezer temperatures.