3. Determination of THC content U.K.
3.1. Preparation of the test sample U.K.
Stems and seeds over 2 mm in size shall be removed from the dried samples.
The dried samples shall be grinded to obtain a semi-fine powder (passing through a 1 mm mesh sieve).
The powder may be stored for 10 weeks at below 25 °C in a dark, dry place.
3.2. Reagents and extraction solution U.K.
ReagentsU.K.
Δ9-tetrahydrocannabinol, pure for chromatographic purposes,
Squalane, pure for chromatographic purposes, as an internal standard.
Extraction solutionU.K.
35 mg of squalane per 100 ml hexane.
3.3. Extraction of Δ9-THC U.K.
100 mg of the powdered test sample shall be weighed, be placed in a centrifuge tube and 5 ml of extraction solution shall be added containing the internal standard.
The sample shall be placed in an ultrasound bath and be left for 20 minutes. It shall be centrifuged for five minutes at 3 000 r.p.m. and then the supernatant THC solution shall be removed. The solution shall be injected into the chromatograph and a quantitative analysis shall be carried out.
3.4. Gas chromatography U.K.
(a)ApparatusU.K.
gas chromatograph with a flame ionisation detector and a split/splitless injector,
column allowing good separation of cannabinoids, for example a glass capillary column 25 m long and 0,22 mm in diameter impregnated with a 5 % non-polar phenyl-methyl-siloxane phase.
(b)Calibration rangesU.K.
At least three points for procedure A and five points for procedure B, including points 0.04 and 0.50 mg/ml Δ9-THC in extraction solution.
(c)Experimental conditionsU.K.
The following conditions are given as an example for the column referred to in (a):
oven temperature 260 °C
injector temperature 300 °C
detector temperature 300 °C