USDA[1] compliant testing of the total THC content in hemp (< 0.3% THC)

Cannabis sativa, the hemp plant, is native to Central Asia and the Indian subcontinent. Throughout history, hemp has widely been used for a broad range of purposes, from production of textile fibers to relief of pain. According to the USDA, industrial hemp may not contain more than 0.3% of THC [1]. With the presented method, multiple hemp samples (up to 14 per plate) can be checked for compliance. Quantitative evaluation is done by scanning densitometry at UV 225 nm.

Scope

The method described below is suitable for testing hemp for compliance with the USDA rule for “Establishment of a Domestic Hemp Production Program” [1]. The same methodology can be applied to marijuana, different types of medicinal grade Cannabis sativa and products thereof, for checking the identity, comparison with reference materials, and quantification of THC and THCA.

Recommended devices

Automatic TLC Sampler 4, Automatic Developing Chamber ADC 2, Derivatizer, TLC Plate Heater 3, TLC Visualizer 2, TLC Scanner 4, visionCATS or: HPTLC PRO SYSTEM with visionCATS

Sample

Prepare hemp or cannabis samples as follows:

In a closed (centrifuge) tube, extract 0.2500 g of dry and homogenized powdered plant material with 10 mL of methanol by sonication for 15 min at room temperature. Then, following centrifugation, transfer the supernatant into a 25.0 mL volumetric flask by decanting (NOTE: do not filter!)

Repeat the extraction once. Dilute the combined supernatants to 25.0 mL with methanol and mix well. Filter through a membrane filter (nominal pore size 0.45 µm) into sample vials.

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