Terpene profiling is fundamental to showing the identity and medical efficacy of cannabis cultivars or strains. Terpenes are the organic primary components of cannabis resins and essential oils with characteristic odor and distinctive organoleptic properties. Made up of volatile and semivolatile combinations of C5 isoprene subunits, terpenes are proposed to synergistically boost the therapeutic effects of cannabinoids by “entourage effect”. As the type and amounts of terpenes differ among genetic lineages of cannabis such as Cannabis sativa, Cannabis indica and Cannabis ruderalis, robust analytical methods and standards are in demand for identification of cultivars, and scientific validation of their medicinal and pharmacological properties.
The increased use of cannabis as a recreational or medicinal drug calls for stringent regulations for manufacturing practices and quality standards derived from cannabis source materials. To address concerns over the therapeutic efficacy, safety and quality of cannabis products, cannabis quality control testing must be carried out for terpenes across geographies, including the United States and Canada, where the landscape of legalization is rapidly changing.
The typical workflow for terpene analysis in cannabis, hemp and their products includes sample preparation by solvent extraction or headspace-based solid-phase microextraction, preparation of standards and calibration,, gas chromatographic separation followed by mass spectrometric detection and data analysis of the terpene profile.
Testing laboratories today prominently use one of the following two techniques for sample preparation in analysis of cannabis terpenes: Simplified solvent extraction or headspace-based solid-phase microextraction (HS-SPME) . Sample preparation typically precedes GC-FID or GC-MS analysis.
HS-SPME technique offers the following benefits:
Solvent extraction also doesn’t require special instrumentation and is a convenient alternative when matrix interferences are not critical.
Profiling and quantitation of terpenes in cannabis products requires the use of authentic and accurate reference standards. Given the isomeric properties of many terpenes, references that characterize the isomer or enantiomer may be important for identification and quantitation. Certified reference materials (CRMs) manufactured according to ISO17034 offer accuracy of concentration with uncertainty and traceability and are recommended for accurate quantitation. CRMs are typically diluted into working standards and calibration curves in the reference range for analysis of the sample.
GC-MS and GC-FID based methods are at the forefront of terpene profiling and quantitation in cannabis terpene testing with excellent ionization response under electron ionization (EI) sources.
GC-MS is an efficient and robust technique to investigate cannabis products for terpenes, providing chromatographic resolution, identification and quantitation. Chiral GC columns can enhance identification by overcoming the challenges posed by isomers and differences in the aromatic character of terpenes. GC x GC techniques are suitable for terpene profiling in complex cannabis matrices, with retention time indexing for greater accuracy.
The use of high-quality standards, reagents and chromatography consumables is a prerequisite for accurate and reliable testing and detection of terpenes in cannabis crops and cannabis-derived products. The correct choice of CRMs, analytical reference standards, high-purity solvents as well as columns form the basis of method development and validation, instrument calibration, quality control and system suitability check.