Sample preparation and homogenization
To measure cannabinoid potency, commercially available hemp was purchased. Hemp flower was placed in a 50 mL conical tube (Omni International, Cat. No. 19–6650), followed by the placement of the active grinding media (Omni International, Cat. No. 19-900 M) specifically for hemp. Tubes were loaded into the BR96 homogenizer (Omni International, Cat. No. 27–0001) in an even parallel series (2, 4, 6, or 8 tubes). Once loaded, the BR96 homogenizer was operated at 25 Hz for 1 cycle (15 s), 2 separate cycles (total of 30 s), 4 separate cycles (total of 60 s), and 6 separate cycles (total of 90 s).
A diamond tap sieves shaker (Esslinger.com, Cat. No. 51.0569) was used. Tap sieve shakers are specified in various standards for particle size analysis. The shaker was used in a horizontal and circular motion, and super-imposed by a vertical motion while administering a taping action. Tap sieve shakers was specified for specific particle size analysis (~ 1.10 mm to 4.50 mm). Starting weight before and after analysis was recorded and distribution percentages were calculated.
Cannabinoid sample analysis for potency
Approximately 100 mg of homogenized flower matrix was isolated and 5 mL of methanol was added. Sample was sonicated, vortexed and centrifugated. Supernatant was diluted with MeOH/H2O (80/20, v/v) + 0.1% formic acid as appropriate for injection. Sample was injected (5 μl) into the Agilent 1220 Infinity II LC. The analytical column used was the Infinity Poroshell 120 EC-C18, 3.0 mm × 50 mm, 2.7 μM at 50 °C. Gradient used was 0 to 1 min, 60% B, 7–8.2 min, 60 to 77% B, and 8.2 to 10 min, 95% B.
Standards for THC, THCA, CBD and CBDA (1 mg/ml) were obtained from Cerilliant (Round Rock, Texas). Standards were combined and a stock solution with a concentration of 250 ppm for each cannabinoid was made and serially diluted in 100% methanol following the dilution series in Table 1. Fifteen μL of each dilution was diluted further with 35 μLs of 100% methanol and analyzed by reverse phase HPLC.
The six (1 mL samples of the 250-ppm cannabinoid) standards were added to reinforced tubes (2 mL) that were pre-filled with 2.8 mm ceramic beads (Omni International, Kennesaw, GA, Cat. No. 19–628). The tubes were processed on the Bead Ruptor Elite Bead Mill Homogenizer at 5 m/s for increasing durations of 10, 20, 30, 60, and 120 s. After each time point, 250 µL was removed to a new 1.5 mL microcentrifuge tube and placed on ice. As a positive control, 500 µL of the 250-ppm cannabinoid standard was placed in a 1.5 mL microcentrifuge tube and heated, at 90 °C, for 180 min. All samples were filtered through a 0.2 µm spin filter and 15 µL of the filtrate was combined with 35 µL of 100% HPLC grade methanol for reverse phase HPLC analysis.
Reverse phase HPLC for standards
Cannabinoid separation and quantification was performed on a Waters 1525 HPLC (Waters Corp, Milford, MA) equipped with a binary pump and 2996 photodiode array detector. Buffer A consisted of ddH2O and formic acid (0.2% v/v) and buffer B was Acetonitrile and formic acid (0.2% v/v). Fifteen μL of each sample was separated on a Raptor ARC-18 150 mm × 4.6 mm, 2.7 μm column over a 20-min linear gradient from 60% B to 100% B at a flow rate of 1.5 mL/min. Absorbance was measured at 280 nm.