Optical and Chemical Characterization and Identification of Crystalline Structures in Cannabis Solvent Extracts


This week (26 September to 01 October 2021), SciX 2021 is being held in Providence, Rhode Island. On Thursday, Microtrace Microscopist Otyllia Abraham will present on “Optical and Chemical Characterization and Identification of Crystalline Structures in Cannabis Solvent Extracts.” The Thursday afternoon session will focus on “Advances in Determination of Molecular Orientation and Interactions by Infrared Spectroscopy.”

To learn more about the conference or this paper, please click here.


Marijuana and hemp represent two broad classes of Cannabis sativa plants that are distinguished based on the concentration of the psychoactive cannabinoid delta-9-tetrahydrocannabinol (Δ9-THC). Cannabinoids are commonly extracted from marijuana and hemp using organic solvents or supercritical CO2 to generate cannabis solvent extracts. These solvent extracts typically contain total concentrations of Δ9-THC or cannabidiol (CBD) (depending on extraction from marijuana or hemp) that are six to eight times more potent than the plant material alone.

Macroscopically, cannabis solvent extracts appear orange/brown in color and can range in texture from glass-like shards to sticky, amorphous materials. Microscopically, at low magnification, the amorphous material is composed of two distinct components: well-formed crystalline material and an amorphous, waxy matrix. Cannabis solvent extracts are typically analyzed by gas chromatography-mass spectrometry (GC-MS) to identify the cannabinoids present. However, using this method, the bulk extract is analyzed rather than the crystalline and wax components separately. As such, characterization and identification of the major cannabinoids present in either the wax matrix or the crystalline component have not yet been accomplished.

In this work, the crystalline components of marijuana-derived and hemp-derived solvent extracts were optically and chemically characterized and identified. For optical characterization, representative crystals were analyzed via polarized light microscopy (PLM). Morphological and crystallographic differences, including optic sign, crystal system, and principle refractive indices, were used to differentiate marijuana-derived extracts from hemp-derived extracts. Analysis of the crystals via infrared (IR) spectroscopy indicated the presence of tetrahydrocannabinolic acid (THCA) in the marijuana-derived crystals and cannabidiol (CBD) in the hemp-derived products. Definitive identification was achieved using single-crystal X-ray diffraction, which also reflected and confirmed the crystal systems determined by PLM. Results from each technique will be presented and comparison of characterization methods and chemical compositions will be discussed.


SciX is national meeting of the Society for Applied Spectroscopy. It is the premier annual conference for scientists in analytical chemistry and its allied sciences. It is presented by FACSS (Federation of Analytical Chemistry and Spectroscopy Societies).

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