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an unapproved pesticide; myclobutanil. It is evident that there is an impetus to develop appropriate analytical techniques for quality assurance and quality control laboratories for cannabis testing. This is necessary in order to build patient and consumer trust.
If ultimately categorised as a regulated pharmaceutical drug, cannabis would be rigorously tested to comply with stringent rules and regulations regarding quality (potency and purity) and safety of the product. However, as there is currently no centralised regulatory body that oversees this, the responsibility of quality assurance falls to the grower, manufacturer and even the consumer.
Gas chromatography (GC) is a widely used analytical tool for cannabis testing. The technique enables potency testing, terpenes profiling, pesticide screening and residual solvents analysis, which should afford potential benefit to significantly the cannabis industry. Typically, the primary cannabinoids of interest for potency testing are: tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN). A key goal in cannabis analysis is positive identification and quantification of the THC/CBD ratio. This is specifically significant for medicinal cannabis, CBD is the primary component of interest as it is often characterised by high levels of CBD and low levels of THC.
In contrast, recreational cannabis typically has high levels of THC – the main psychoactive ingredient – and low levels of CBD. Analytical instrumentation, such as GC, has long been perceived to require extensive experience in the laboratory, with training in chromatography or a deep understanding of analytical chemistry. However, with the increased need for quality control and quality assurance in the dynamic cannabis industry, GC technology is now more accessible to smaller companies and adapted for users with minimal GC experience. Newer instrumentation is more compact, cost-effective and ultimately, easier to use. While these instruments are no replacement for an independent accredited laboratory, these instruments can give growers and processors an accurate result of cannabinoid percentages. This is fundamental information to growers and dispensaries while simultaneously encouraging the uptake of testing and responsibility within the industry.
Shamanics use an Ellutia 200 Series GC for quality assurance of its products and
Figure 1: The Decarboxylation of THCA
Figure 2: The Derivatisation of THCA
offer a testing service for coffee shops in Amsterdam to test the quality of their cannabis. The company conducts terpene analysis and potency testing. When testing for potency, they analyse total THC and CBD. Each total cannabinoid value is calculated by adding the amount of neutral version present together with the amount of neutral version that could be created by the decarboxylation of the acidic version of the cannabinoid present. When testing by GC, the acidified versions of the cannabinoids get converted to the neutral forms in heat of the GC injector. Figure 1 shows the conversion of THCA to THC in the GC injector.
If they need to see both the acidified and neutral versions, they can do this by derivatising the sample (Figure 2). This additional process is required because the heat of the injector converts the THCA to THC in the injector so it is not then present to analyse and just becomes one large THC peak. The derivatised THCA is not converted in the injector so can be separately analysed. Accuracy is crucial in order to judge the quality of a product, and relay this information to the retail environment.
Experimental Terpene and Potency in a single analysis
The Chromatogram in Figure 3 shows the concentration and profile of the terpenes and cannabinoids in a cannabis sample in order to establish the potency, the flavour profile, strength and therefore, quality.
Materials
0.1 g of cannabis was added to 30 mL of methanol at ambient, shaken for 30 seconds
and left to extract for 30 minutes. See Figure 4. An aliquot of the extractant liquid is then collected through a syringe filter and placed in a sample vial ready for analysis. The analysis was performed using a 200 Series GC, see figure 5, with an FID (Ellutia, Ely, UK) and a 30m 0.25 x 0.25 EL-5 Column. The standards used for the calibration were a standard 3 component cannabinoid mix (Restek Cat.# 34014: Cannabinoids Standard (3 components)) and a 19 component terpene mix (Restek Cat.# 34095: Medical Cannabis Terpenes Standard #1 (19 components).
GC Conditions
Injector Temperature 270˚C Detector Type
FID
Detector Temperature 280˚C Carrier Gas Type Detector Range Carrier flow Split Flow
Injection volume Stabilisation time
Column Type
Initial Temperature Hold
Ramp 1
Temperature 1 Ramp 2
Temp 2 Total run time
Hydrogen x10
1.5 mL/min 70 mL/min 1 µl
0.5 min
EL-5 30 m x 0.25 mm id x 0.25 µm film thickness
100˚C 5 min
20˚C/min 200˚C
10˚C/min 270˚C
17 min
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