Planta Med 2006; 72 - P_260
DOI: 10.1055/s-2006-950060

The Use of Near Infrared Spectroscopy to discriminate between THC-rich and hemp forms of Cannabis

N Wilson 1, M Heinrich 1
  • 1Centre for Pharmacognosy and Phytotherapy, The School of Pharmacy, University of London, 29–39 Brunswick Square, London, WC1N 1AX, UK

The main psychoactive component of 'drug type' cannabis, Tetrahydrocannabinol (THC), is present at only very low levels in hemp, which is often used in the food and textile industry.

Near Infrared (NIR) spectroscopy is ideally suited to the identification and quality control of plant material. This work illustrates of potential of NIR spectroscopy to differentiate between 'drug type' cannabis and hemp. The different plant materials were scanned on a FOSS NIRSystems 6500 spectrophotometer with the Rapid Content Sampler module and Vision® software.

A spectral library containing samples of THC-rich cannabis or hemp in the form of dried flowering tops or leaf was constructed and samples were assigned as either 'high THC' or 'low THC'. The use of spectral correlation methods allowed for the correct identification of all samples in the library.

Principal Component Analysis (PCA) (The Unscrambler® software) was also carried out on the spectral library and the scores plot discriminated between the 'high' and the 'low' THC content samples. The first Principal Component loading correlated with the NIR spectrum of THC, further supporting the evidence that the differences seen between the two sets of samples were due to the THC content.

The library was 'interrogated' with further samples, which included material with the cannabinoids removed by solvent extraction and old samples of 'drug type' cannabis. The scores plots obtained were consistent with their THC content. This demonstrated the robustness of the analytical models used to discriminate between the THC-rich and hemp forms of Cannabis.