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How to Ensure a Contaminant-free Cannabis Product

By Toby Astill

Published: Jun 13, 2019   
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Ensuring a contaminant-free cannabis product is no mean feat. Several factors contribute to this, including the industry’s ability to keep up with the meteoric rise of legalized cannabis, increasingly stringent regulations, and the wide range of product forms - from edibles and flowers to creams and oils - that need to be analyzed. Taken together, these factors can lead to inexperienced – and even experienced – labs failing to meet regulatory requirements.

To overcome the unique challenges associated with analyzing cannabis and hemp products, and to meet regulations, it's crucial for labs to focus on four key testing areas: the contaminants of residual pesticides and mycotoxins, heavy metals, and solvents, as well as quantifying THC/CBD potency.

Pesticide and mycotoxin analysis

As with any crop, cannabis and hemp plants can easily come into contact with pesticides throughout their growth cycle. To add to this, cannabis is grown and processed in environments susceptible to fungi growth, which can lead to the presence of carcinogenic mycotoxins such as ochratoxin A and aflatoxins. These toxins can culminate in the final product, making testing and identification of paramount importance. This is particularly relevant if the product is intended for medicinal purposes where patients could be immuno-compromised.

Traditionally, a combination of both GC/MS/MS and LC/MS/MS has been used for pesticide and mycotoxin analysis. However, modern spectrometers can incorporate multiple ionization sources, enabling the analysis of all pesticides and mycotoxins currently regulated in North America. This includes not only heat-labile compounds like daminozide, but also chlorinated or hydrophobic compounds normally analyzed by GC/MS/MS. Using just one instrument to analyze all regulated pesticides and mycotoxins enables the entire analytical process to be streamlined. This is a big benefit for the growing cannabis industry, saving labs money and eliminating the need for more time-consuming preparation methods. 

Sensitivity is another important factor in an industry where a plethora of regulations are being navigated. Labs in North America need to base their instrumentation on an understanding that regulatory limits for contaminants are getting progressively lower. It's also critical they are aware that the industry is evolving and that future-proofing methods and instruments are important to ensure the continued safety of consumers.

Quantifying heavy metals 

Cannabis and hemp plants are extremely efficient at absorbing heavy metals from the environment and although these elements have important biochemical and physiological functions, they are also extremely toxic to humans at higher concentrations. This is a particular worry for long-term users of cannabis and hemp products, such as those who suffer from epilepsy, as they can accumulate in the body and cause serious harm. 

The FDA currently recommends that the four elements cadmium, arsenic, lead and mercury be analyzed in all drug products, excipients, and substances. Because the determined safety of a cannabis or hemp product is dependent on the final form it takes and whether it's inhaled or ingested, it's critical that instruments used to analyze these products are reliable and effective. 

Inductively coupled plasma mass spectrometry (ICP-MS) is generally considered the gold standard for measuring heavy metal content in cannabis and hemp products. This instrument offers users superior sensitivity, enabling the detection of metals in the sub-parts per billion concentrations. The wide variety of cannabis forms available means a robust sample preparation method is needed. This typically consists of homogenization followed by microwave digestion to break down the complex cannabis or hemp matrix and extract the heavy metals for quantification and identification. 

Residual solvent detection

Cannabis and hemp concentrate products such as edibles, tinctures, extracts, and oils are quickly becoming the most widely used legal products in the market. Most of these concentrates first need to be extracted using solvents such as supercritical CO2, butane, or ethanol. Because of this, it's possible that solvents can remain in the product as it makes its way through production. Due to the health impact these chemicals pose, it's important to analyze and remove residual solvents before products reach consumers.

Residual solvents can be measured using headspace GC/MS. The headspace component of this approach enables the residual solvents to enter the analytical system while the non-volatiles remain within the sample. It also requires minimal sample preparation, resulting not only in easy maintenance for the user, but also a faster analysis time. Using MS as the detection method ensures that any residual solvents that co-elute are also identified. An added bonus is that it enables non-target compounds to be identified, preventing any false positives from skewing results and meaning entire batches of cannabis or hemp could be saved from unnecessary destruction. 

Potency evaluation of THC and CBD

There are numerous reasons why the potency of THC or CBD might need to be evaluated in a cannabis or hemp product. For starters, understanding the THC/CBD ratio of your product is important for determining the therapeutic value of a crop. It's also critical in differentiating between cannabis and hemp varieties. The 2018 Farm Bill defined hemp as a form of cannabis containing a tetrahydrocannabinol (THC) concentration of “no more than 0.3 percent on a dry weight basis.” Although hemp is now legal at a federal level, different states across the US still have different THC testing methods. This means that a plant that tests at or below 0.3 percent THC in one state could be found to have a higher level in another. It's therefore critical that labs use instrumentation that is as accurate and reliable as possible. 

Both GC and HPLC can be used to determine potency, each providing different advantages. Generally, HPLC is preferred as it is able to identify THCA and CBDA, the native acidic forms that are present in the plant material. These acidic forms convert to THC and CBD when heated, for example in the injector port of a GC or when smoked. This method is therefore often preferred for edible materials and extracted tinctures, or for determining potency in the original plant material. 

Realizing the potential in cannabis analysis

While increasingly stringent state-by-state regulations come to the fore and calls for national testing standards continue via efforts like Emerald Scientific’s testing badges, labs need instrumentation that can ensure their products will stay up to date and remain safe. 

By looking to more mature markets, such as food and drink, technology partners can help labs overcome the many challenges associated with constantly evolving regulations. The underlying technologies discussed previously have already been successfully applied in other industries, to identify and quantify contaminants. Labs can now leverage these technologies, ensuring growing markets, such as cannabis and hemp, do not fall behind and are able to reach their full potential. 

Toby Astill

Global Market Manager for Cannabis and Hemp at PerkinElmer, Inc.

Toby has a PhD in Chemistry and has spent the last 11 years working for PerkinElmer and driving its global cannabis and hemp business through a variety of initiatives, including market and industry research, collaboration agreements with customers, application content development, and field marketing initiatives. He has written for Analytical Cannabis since 2019.


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