Journal:An assessment of solvent residue contaminants related to cannabis-based products in the South African market
| Full article title | An assessment of solvent residue contaminants related to cannabis-based products in the South African market |
|---|---|
| Journal | Journal of Cannabis Research |
| Author(s) | Viviers, Hendrik J.; Petzer, Anél; Gordon, Richard |
| Author affiliation(s) | National Analytical Forensic Services, North West University |
| Primary contact | Email: henrick at nafs dot co dot za |
| Year published | 2022 |
| Volume and issue | 4 |
| Article # | 19 |
| DOI | 10.1186/s42238-022-00130-3 |
| ISSN | 2522-5782 |
| Distribution license | Creative Commons Attribution 4.0 International |
| Website | https://jcannabisresearch.biomedcentral.com/articles/10.1186/s42238-022-00130-3 |
| Download | https://jcannabisresearch.biomedcentral.com/track/pdf/10.1186/s42238-022-00130-3.pdf (PDF) |
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This article should be considered a work in progress and incomplete. Consider this article incomplete until this notice is removed. |
Abstract
Organic solvents are used for manufacturing herbal medicines and can be detected as residues of such processing in the final products. It is important manufacturers control the presence of these solvent residues for the safety of consumers. South African cannabis-based product samples were analyzed for solvent residue contaminants as classified by the United States Pharmacopeia (USP), chapter 467. The origin of these samples ranged anywhere from crude extract to product development samples and market-ready final products. Samples were submitted to a contract laboratory over a period of two years, from 2019 to 2021. To date, no data of this kind exist in South Africa, specifically relating to cannabis-based medicinal, recreational, or complementary products.
A total of 279 samples was analyzed in duplicate by full evaporation headspace gas chromatography–mass spectrometry (GC–MS), and the results were reported in an anonymized format. The results showed an alarming 37% sample solvent residue failure rate with respect to adherence to the USP 467 specification. This research highlights the importance of ensuring regulations are enforced to control product quality. Additionally, it highlights how the South African public need to be educated about the risks associated with cannabis-based products.
Keywords: residual solvents, ethanol, isopropanol, South Africa, medicinal cannabis, chromatography, GC–MS, cannabis oil, plant extracts
Background
It is imperative to subject herbal preparations, medicines, and recreational products to quality control. For the pharmaceutical industry—as well as cannabis in general—there are an abundance of control measures in place to ensure product safety and efficacy. (WHO, 2007; Viviers et al., 2021) A range of organic solvents are used for manufacturing herbal medicines and can be detected as residues of such processing in the final products. Medicinal cannabis extracts and other processed forms may thus contain residual solvents. This is especially relevant to extracts, which have a sticky and viscous nature that make it difficult to remove solvents. (Romano & Hazekamp, 2013) The most common examples of such cannabis extracts are termed “Rick Simpson oils” or “FECOs” (full extract cannabis oils).
Cannabinoids, as well as terpenoids and flavonoids, are extracted by a solvent, followed by an evaporation step in order to increase the concentration of these compounds in the extract. (Romano & Hazekamp, 2013; Hazekamp, 2006) These types of cannabis oils or extracts are becoming increasingly popular amongst self-medicating patients because of the simplicity and low cost involved in producing the oils. (Romano & Hazekamp, 2013) After solvent evaporation, residues are still present in the extract, and the concentrations of the solvent residues should be controlled through good manufacturing practice (GMP) and quality control of the final products. (International Community of Harmonization (ICH), 2011) To ascertain whether a product is safe for chronic human consumption, the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH), as well as the United States Pharmacopoeia (USP), have listed predetermined solvent residue limits. Solvents are classified into the following categories by the ICH (International Community of Harmonization, 2011) and the USP (United States Pharmacopeia, 2009) according to their potential risks:
- Class 1: Solvents to be avoided as they are potentially carcinogenic, such as benzene;
- Class 2: Solvents with toxic potential, such as methanol or acetonitrile; and
- Class 3: Solvents with limited toxic potential, such as ethanol.
Residual solvents are primarily analyzed by [[headspace gas chromatography–flame ionization detection (GC-FID) or liquid injection GC-FID (United States Pharmacopeia (USP), 2009). The alternative use of mass spectrometry (MS) detection may provide additional selectivity for co-eluting solvents.
In this study, a published analytical method was employed as basis for the development of the final analysis method for residual solvents. (Hilliard et al., 2009) As a result of the viscosity of most of the cannabis extracts, liquid injection is not feasible. Although the ICH and USP provide a guideline that lists the solvents which should be included in a working list (International Community of Harmonization, 2011; United States Pharmacopeia, 2009), the solvents that inevitably get analyzed are ultimately decided by each manufacturer or quality control laboratory.
Based on interaction with cannabis extract manufacturers, Table 1 was compiled and provides a list of the solvents that have been analyzed for each class. This list is by no means exhaustive and could be altered to include additional solvents. Few manufacturers employ Class 1 and 2 solvents; nonetheless, they are included here.
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References
Notes
This presentation is faithful to the original, with minor changes to presentation; grammar and spelling required more cleanup for improved readability. In some cases important information was missing from the references, and that information was added. The original article listed references in alphabetical order; this version lists them in order of appearance, by design.
