Mycotoxins in cannabis and associated products

Over the past decade, the cannabis market has grown considerably following legalisation for medicinal or recreational use in various countries. It has been estimated that in the US alone, sales of cannabis products will exceed $2 billion over the next four years and an estimated market potential of over £8 million per year in the UK. As the sales of cannabis increase, so does the quantity produced worldwide. However, cannabis may contain toxic compounds such as pesticides, pathogens, and mycotoxins therefore, analysis of cannabis and cannabis products is essential to maintain safe and high-quality goods. 

Mycotoxins in cannabis is not a new finding. In fact, there was a publication dating back to the 1970’s showing that under favourable conditions, Aspergillus flavus and Aspergillus parasiticus could flourish and produce aflatoxins on moist marijuana plants. There appears to have been little or no follow-up to these observations, probably as at that time they largely concerned the safety of an illegal substance. However, legalisation of consumption of cannabis products now brings safety to the forefront and such products need to be scrutinized for contaminants such as mycotoxins to the same extent as food or pharmaceuticals. This means applying the same safety values for mycotoxins as applied to foodstuffs and conducting routine monitoring to ensure standards are maintained.

Regulations are in place for cannabis which outline the maximum residue limits for various contaminants including mycotoxins. The levels for total aflatoxin range from 4 ppb in Europe and Australia to 20 ppb in the USA and Canada whereas only the USA has legislation at present for ochratoxin at a level of 20 ppb. These levels are not too different from the legislative levels typically applied to food for direct human consumption. Aflatoxin and ochratoxin often are found to co-occur, therefore a multi-toxin approach could be advantageous, and many laboratories are considering multi-analyte analysis to reduce overhead costs.

There are several options available to laboratories analysing cannabis and associated products. The first is to use direct injection or dilute and shoot methods. These are typically used prior to LC-MS/MS detection however, they are simple and could result in some matrix effect being observed. Similarly, solid phase columns are a basic form of clean-up and are mainly used for the analysis of simple commodities like certain cereal samples.

The analysis of mycotoxins in cannabis products is quite challenging due to the diverse physico-chemical nature of the toxins and the difficult nature of the cannabis matrices from which the toxins need to be extracted. The plant material is highly pigmented and contains oils and cannabis resins are highly viscous materials. The extraction and clean-up procedures need to be capable of extracting the toxins and isolating them whilst also removing the sample matrix.

Immunoaffinity columns are often used in Official Methods and have found to be highly specific. This form of clean-up is particularly suitable for the analysis of complex samples such as cannabis and cannabis products as all interfering components are removed giving you added confidence in your analysis which can ultimately help to reduce the number of samples re-analysed.

Immunoaffinity columns have been available for many years however, analysis requirements are changing and therefore, more and more multi-toxin columns such as AFLAOCHRA RHONE^® WIDE and AO ZON PREP^® are now available on the market. The beauty of employing an immunoaffinity column clean-up is that irrespective of matrix, the method follows the same tried and tested steps. The efficiency of the extraction of the toxin/s from the matrix needs to be demonstrated, but otherwise the versatility of immunoaffinity column clean-up ensures ease of analysis by either HPLC or LC-MS/MS without matrix interference. The use of multi-mycotoxin immunoaffinity columns also presents an opportunity to manage increasing demands while still maintaining quality results particularly for cannabis and cannabis products where both aflatoxin and ochratoxin may be analysed.