Cannabis, whose medicinal properties have been known for centuries, is among the most popular illicit drugs. The legalization of cannabis products for medicinal and recreational purposes has raised the need for accurate and reliable analysis and testing methods to ensure their efficacy and regulatory compliance.
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Introduction
Medicinal cannabis is used in the treatment of several conditions, including chronic pain, depression, anxiety, and neurological disorders. Laboratories across the world conduct routine analyses on various cannabinoids from different matrices.
The primary psychoactive analyte of cannabis is tetrahydrocannabinol (THC). Other important compounds are cannabinol (CBN) and cannabidiol (CBD), which, unlike THC, have no psychotropic properties and display different pharmacological effects.[1]
Cannabis testing is crucial to differentiate between legal or illicit consumption, determine the concentrations of active components, and ensure standards are met in order to protect consumer health and maintain product consistency.
Overview of Cannabis Testing
In some regions, regulatory requirements mandate rigorous testing to ensure that cannabis products are safe for consumption. Assessing cannabinoid content, detecting contaminants such as heavy metals and pesticides, and verifying product consistency, are used to determine the potency of cannabis products (amount of THC and CBD) and their therapeutic potential.
Common analytical techniques for cannabinoid profiling include gas chromatography (GC) and high-performance liquid chromatography (HPLC), with the latter favored for the analysis of non-volatile and thermally labile compounds.
Analytical Techniques in Cannabis Testing
Given the complexity of most matrices, sample preparation is a fundamental step for effective cannabis testing. Procedures include homogenizing the samples, extracting the analytes, and removing interferences.
The most widely used extraction methods for cannabinoid analysis are liquid-liquid extraction (LLE) and solid-phase extraction (SPE), while purification steps include filtration and centrifugation.
One of the most common techniques for cannabis analysis is GC, often used in conjunction with flame ionization detection (FID) or mass spectrometry (MS). GC offers high sensitivity and resolution but requires cannabinoids to be in a vaporized state, often demanding derivatization.[2]
HPLC is generally used for quantitative cannabis analysis. C18 columns have high resolution and can separate a broad spectrum of cannabinoids in acidic and neutral forms without derivatization.
Supercritical fluid chromatography (SFC) is a newer technique that utilizes supercritical CO2 as the mobile phase and combines the advantages of HPLC and GC. It offers efficient separation with reduced solvent usage and faster run times.
Nuclear magnetic resonance (NMR) is less sensitive to impurities than GC and HPLC. Methods for rapid cannabinoid quantification (5-min analysis time) via 1H-NMR have been developed. One of the major advantages of NMR is that it does not require reference standards, although the technique's high costs are a significant downside.
MS coupled with chromatography techniques enhances the sensitivity and specificity of cannabinoid detection, allowing their identification at very low concentrations. Fourier-transform infrared (FTIR) spectroscopy offers rapid and non-destructive methods to identify functional groups within cannabinoids and contaminants.
Contaminant Testing
Pesticides and residual solvents can pose significant health risks. Naturally occurring contaminants such as fungi, bacteria, and heavy metals present in soil are also potential cannabis contaminants.
Cadmium, arsenic, mercury, and lead are among the heavy metals most commonly associated with poisoning in humans. Other substances, such as glass beads, are sometimes used to add bulk and to mimic the crystalline appearance of the resin glands, which contain large amounts of THC.[3]
Hence, ensuring cannabis products are free from harmful contaminants is critical for consumer safety. Techniques such as LC-MS and GC-MS are used to detect these contaminants at trace levels.
Inductively coupled plasma mass spectrometry (ICP-MS) can assess heavy metals, while polymerase chain reaction (PCR) is a standard method for detecting microbial contaminants, offering high sensitivity and specificity.
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Advancements and challenges in Cannabis Testing
With a need to detect low levels of THC, differentiate its various isomers, and identify other cannabinoids that might be present, the analysis of cannabis products is quite complex. This requires reliable, reproducible, and sensitive analytical methods and techniques.
Automation and high-throughput technologies are transforming cannabis testing. Robotic sample preparation systems and automated chromatography platforms enhance efficiency and accuracy, reducing human error and increasing throughput.
Biosensors and portable testing devices are emerging innovative approaches for the on-site analysis of THC from easy-to-collect media such as sweat or saliva. Portable devices also have advantages such as a user-friendly platform, fast results, and mobility.
Immunoassays are widely used for on-site THC sensing, where the analysis from saliva can allow the detection of THC in a range between 2 and 190 ng/mL in as fast as 5 min. Samples from the sweat of the fingers can be collected on a cartridge and inserted into a portable reader, affording results in 10 min. Portable breath analyzers for the detection of THC based on the fluorescence of the diazonium salt of rhodamine 123 are under development.[4]
Despite these advancements, the lack of standardized testing protocols remains a challenge. Establishing industry-wide standards and quality control measures is essential to ensure consistency and reliability across laboratories.
Conclusion
Comprehensive and accurate methods for cannabis testing are crucial. Advances in analytical techniques, including chromatographic and spectroscopic methods, and the rise of new portable technologies are expanding the capacity for cannabis analysis.
Continued innovation and the establishment of standardized testing protocols will be crucial to maintaining high standards and ensuring regulatory compliance and product safety.
References
- Antunes, M., Barroso, M. & Gallardo, E. (2023). Analysis of Cannabinoids in Biological Specimens: An Update. Int J Environ Res Public Health, 20.10.3390/ijerph20032312.
- Pourseyed Lazarjani, M., Torres, S., Hooker, T., Fowlie, C., Young, O. & Seyfoddin, A. (2020). Methods for quantification of cannabinoids: a narrative review. Journal of Cannabis Research, 2, 35.10.1186/s42238-020-00040-2. Available: https://doi.org/10.1186/s42238-020-00040-2
- Mclaren, J., Swift, W., Dillon, P. & Allsop, S. (2008). Cannabis potency and contamination: a review of the literature. Addiction, 103, 1100-9.10.1111/j.1360-0443.2008.02230.x.
- Clément, P., Schlage, W. K. & Hoeng, J. (2024). Recent advances in the development of portable technologies and commercial products to detect Δ(9)-tetrahydrocannabinol in biofluids: a systematic review. J Cannabis Res, 6, 9.10.1186/s42238-024-00216-0.
Further Reading