45
Figure 2: Products of the thermal degradation of the monoterpene limonene when heated at 120°C for 24 hours. Degradation of Limonene was monitored by GC-FID. 50% of Limonene degraded in 24 Hours into the compounds depicted above [5].
units (Figure 1). An isoprene unit is a 5-carbon molecule upon which terpenes are built. Combining three isoprene units forms a class of compounds called sesquiterpenes which are less volatile than monoterpenes. The largest and least volatile terpenes are biosynthesised by the joining of four or more isoprene units.
Terpenes are both volatile and thermolabile compounds. They easily convert into each other by oxidation, isomerisation, cyclisation or dehydrogenation reactions (Figure 2). The environment in which Cannabis is stored and the methods used in processing will effect the chemical composition of these isoprene-containing compounds. For example, distillation of crude Cannabis oil raises two issues. First, due to the high temperature required for distillation, delicate monoterpenes readily thermally degrade. Second, during distillation organic solvents co-elute with the terpene fraction. If this terpene fraction is used
in Cannabis oil formulation, these organic solvents will contaminate the final product.
Supercritical fluid extraction (SFE) is an effective method for the separation of monoterpenes from sesquiterpenes, their alcohol derivatives, and cannabinoids. The most popular supercritical solvent used is carbon dioxide (CO2
). CO2 Experiment 1 is inexpensive and
is a generally recognised as safe solvent. CO2 reaches supercritical state at conditions of 31°C
and 74 bar and returns to a gaseous state at ambient conditions. This allows for simple solute recovery and results in a solvent-free extract [6]. By modifying the pressure and temperature of the CO2
In order to develop terpene extraction conditions it is critical to understand the relative solubility of terpenes in supercritical carbon dioxide. Solubility data exists for cannabinoids in supercritical carbon dioxide [[2], but limited literature is found on the solubility of terpenes. In Experiment 1, we increase our understanding of the elution order of monoterpenes and their separation from sesquiterpenes at different supercritical carbon dioxide conditions.
system, the dissolution
properties of the solvent can be adjusted, enabling a selective extraction of cannabinoids and terpenes. Here we describe a systematic approach to developing terpene extraction conditions utilising supercritical carbon dioxide
To develop and optimise conditions for terpene extraction using supercritical carbon dioxide, we used the Investigator Supercritical Fluid Chromatography (SFC) instrument (Waters, Milford, USA). Typically, the Investigator SFC system is used for analytical and semi-preparative purification work [7]. However, with a few
Figure 3: Investigator SFC System/experimental design.
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