Oxidation is a chemical degradation process in which a cannabinoid changes through oxidation reactions. In practical cannabinoid handling, this is often associated with prolonged exposure to oxygen and can be accelerated by factors such as light and heat.
Oxidation does not necessarily happen suddenly. It can occur gradually during storage, handling or repeated opening of a container, slowly changing the chemical composition of the material.
A well known example is the gradual degradation of Delta-9-THC toward CBN under oxidative ageing conditions. The exact degradation pathways depend on the cannabinoid, formulation and environment, so different cannabinoids can behave differently over time.
Factors that can accelerate oxidation include:
What can oxidation change?
Cannabinoid composition
Oxidation can reduce the concentration of the original cannabinoid while increasing the concentration of oxidation or degradation products.
Colour
Oxidative degradation can contribute to gradual darkening or other colour changes, although appearance alone cannot identify the underlying chemical change.
Product consistency
Materials with different storage histories can gradually develop different chemical profiles even when they originally came from the same batch.
Analytical profile
Degradation can lower the measured concentration of the original cannabinoid and introduce additional degradation products into analytical results.
Oxidation during cannabinoid storage
Oxidative degradation can be relevant both for bulk cannabinoid material stored in a closed laboratory jar and for a finished cannabinoid formulation stored inside a cartridge.
A closed jar can still contain oxygen in its headspace. Storage temperature, light exposure, storage duration and repeated opening can therefore remain relevant.
Finished cannabinoid formulations can also change during storage. The cartridge does not eliminate the influence of time, temperature, light and oxygen already present inside the system.
How to minimise cannabinoid oxidation
Limit oxygen exposure
Keeping containers properly closed when material is not being handled reduces unnecessary exchange with surrounding air and limits continued oxygen exposure.
For storage where tighter control is required, the oxygen-containing headspace can also be reduced or replaced with an inert gas such as argon. An inert atmosphere lowers the amount of oxygen available to participate in oxidative reactions.
Store material out of light
Cannabinoid material should generally be stored away from unnecessary light exposure. Opaque containers, amber glass or storage inside a closed cabinet, drawer or other dark environment can reduce light-driven degradation.
Direct sunlight and prolonged exposure to strong artificial light are particularly undesirable for long term storage.
Reduce excessive headspace and repeated opening
A large partially empty container contains more air above the material than a more appropriately sized container. Reducing unnecessary headspace can therefore reduce the amount of oxygen stored alongside the cannabinoid.
Repeatedly opening a container also replaces part of the internal atmosphere with fresh surrounding air, introducing additional oxygen over time.
Use appropriate cold storage
Chemical degradation generally proceeds more slowly at lower temperatures. Depending on the cannabinoid and formulation, refrigeration or frozen storage can therefore help improve long term stability.
The appropriate storage temperature depends on the specific substance. Some materials are suitable for refrigeration, while others may tolerate freezing. Formulations containing multiple ingredients should be assessed according to the storage requirements of the complete mixture.