Sample preparation of cannabis plants
For thousands of years, cannabis has been employed as a medicine in various cultures. For example, as hashish (the resin of the female plant), or as marijuana (dried leaves and flowers).
Today, cannabidiol (CBD) and tetrahydrocannabinol (THC) are particularly isolated and researched from the various active substances which are contained in the plant (in addition to other terpenes and cannabinoids) as pharmacologically effective components.
Sticky and Tricky
The translucent structures which are produced from the cannabis flower are trichomes. These structures are sticky and resinous and contain most of the biologically active terpene and cannabinoid compounds. This is a difficult material for milling, as seen in the image.
The cannabis active ingredients are used therapeutically as:
- Appetite stimulation
- Pain reliever
Supercritical CO2 Extraction
Supercritical CO2 extraction is the most frequently used technique for extracting the active ingredients from the cannabis plant. With high pressure at over 31 °C the CO2 gets into the "supercritical" state.
It now acts as a solvent and it is passed through a chamber containing the plant material. The CO2 can fill the entire chamber like a gas but still possesses the density of a liquid. This is perfect for extraction as it does not cause damage or denaturation to the product.
The CO2 extracts the terpenes and cannabinoids from the plant. The result is a safe, high-quality, pure oil, which can now be processed for a number of therapeutic applications.
Naturally, the producers of these cannabis oils want the extraction process to be as efficient as possible, which means the optimum possible yield of the ingredients in the shortest possible time.
Homogeneous Grinding of Cannabis
To accomplish this, an optimal, homogeneous grinding of the cannabis plant must be performed. The FRITSCH PULVERISETTE 19 – a Universal Cutting Mill for fine grinding and for precise comminution, is the ideal instrument for this.
Inhomogeneous sample - sample preparation with a food blender.
Homogeneous sample - sample preparation with the Universal Cutting Mill PULVERISETTE 19.
Perfect Grinding Chamber Geometry
In cutting mills, the sample is shredded between the knives of the rotor and the counter knives in the grinding chamber, employing the principle of a pair of scissors to generate the final fineness desired.
Minimal dead space is ensured by using the unique grinding chamber geometry of the FRITSCH Universal Cutting Mill PULVERISETTE 19. The special airflow is the basis for fast, clog-free work and quick residue-free cleaning.
The progressive cutting geometry between the rotor and stator knives actively transports the sample material so it cannot get stuck anywhere. Furthermore, the utilization of the stainless-steel high-performance Cyclone separator ensures high throughput.
A negative pressure is produced in the grinding chamber with the help of the high-performance Cyclone separator and an industrial vacuum cleaner. The material is fed into the FRITSCH PULVERISETTE 19 via a funnel. Different sieve cassettes define the final fineness of the cannabis sample.
Ground material has a bulk density of 225-250 g/liter, while unmilled cannabis plant material has a bulk density of 100-125 g/liter. The sample is homogenized optimally by the grinding and much more material can be filled into the extraction column, which also increases the yield per extraction significantly.
Which degree of grinding provides the optimum for the most efficient extraction was explored by FRITSCH together with OutCo, a cannabis producer in California, USA. The 2 mm sieve achieved the best results. Other screens may be utilized for different fractions.
More PULVERISETTE 19 Facts
The FRITSCH Universal Cutting Mill PULVERISETTE 19 is also employed to grind samples to examine the material for pesticide residues or for potency testing. The speed of the rotor can be regulated between 300 rpm to 3000 rpm in order to optimally adapt the cutting performance to the sample.
FRITSCH Universal Cutting Mill PULVERISETTE 19.
Simple cleaning is desirable, as with all mills employed in analytical laboratories. The concept of the Clean Design was utilized for the FRITSCH PULVERISETTE 19: the grinding chamber can be opened fully, all grinding parts can be removed without tools for quick and easy cleaning and cross-contamination can be effectively avoided.
For utilization in the pharmaceutical sector, the FRITSCH PULVERISETTE 19 is also available in a 316L stainless steel version.
This information has been sourced, reviewed and adapted from materials provided by FRITSCH GmbH - Milling and Sizing.
For more information on this source, please visit FRITSCH GmbH - Milling and Sizing.