Chemistry Horticulture

Removing Pesticides from Cannabis Concentrates

Leo Zhou
Written by Leo Zhou

Cannabis concentrates have a problem with pesticides; Flash chromatography has been proven to remove pesticides efficiently.

Like any crop, cannabis plants are prone to pests and disease. Some of which include tiny leaf-sucking spider mites, which can spawn a new generation in less than one week, to powdery mildew, a fungus that forms a talcum-like coating on leaves and spreads rapidly through greenhouses. For every other agricultural product, there is a relatively clear solution: find a pesticide labeled for the specific plant or setting, and apply it according to the instructions.

This is not the case with cannabis. Discrepancies between state and federal laws have left cannabis farmers without any approved pesticides for use on their crops. As a result, some growers have taken the matter into their own hands, treating their plants with alarmingly high levels of pesticides intended for other uses1.

Many cannabis products contain pesticides at levels higher than what’s typically allowed for edible or smokable products.

Some cannabis farmers in California spray their plants with chemicals such as avermectin (used in Avid insecticide), myclobutanil (used in Eagle 20 pesticide) and bifenazate (used in Floramite). Exposure to these chemicals has proven toxic or even carcinogenic; resulting in symptoms including vomiting, rash, nosebleed, tremors, and coma.

In some cases, up to 80 percent of cannabis concentrates that are tested show signs of pesticides. Of particular concern were the concentrates used to make candies, baked goods, and other edibles. Examples include samples of cannabis concentrates with levels of carbaryl as high as 415 parts per million (by comparison, the tolerance for carbaryl on blueberries is three parts per million). Carbaryl is a chemical typically used on fruits, vegetables, and ornamental plants. As well as Myclobutanil, a fungicide used to fight powdery mildew on vegetables, fruits, and leafy greens, was found between 44 and 392 parts per million in concentrates (levels allowed on food items usually range from 0.1 to 10 parts per million)2.

Some states such as Oregon and Washington, already have state regulations, which permit 100 parts per billion to 2,000 parts per billion, depending on the compound. Under California’s Medical Marijuana Regulation and Safety Act, passed last year, state oversight (including mandatory product testing) will begin in 2018. In the Medical Cannabis Testing Laboratories Initial Statement of Reasons, each pesticide is identified with the California Pesticide Residue Monitoring Program minimum detection limit and the reason for concern. For example, Myclobutanil is 200 parts per billion and Carbaryl is 100 parts per billion3.

Making pesticide-free concentrates is becoming critical. Flash Chromatography has been used to purify mixtures in pharmaceutical and chemical industries for decades; including natural product separation and isolation. Chromatography separation, based on compound polarity, is the most efficient way to purify a complicated mixture such as cannabis concentrates.

To address this concern, a study was initiated utilizing the BUCHI Reveleris® X2 Flash Chromatography system, C18 as the stationary phase, and Ethanol/Water as the mobile phase. The methodology developed proved successful in removing pesticides from concentrates as detailed in the table below. The residue testing report shows the pesticide content before and after purification using the Reveleris® X2.

The total pesticides have been reduced from 365,854 PPB to 708 PPB. Main residues such as Bifenazate, Carbaryl, Malathion, and Myclobutanil have been completely removed. Permethrin appears to be the most challenging of the pesticides in this study to remove since this compound’s polarity closely resembles that of THC, but it was significantly reduced after the purification. We believe that Permethrin residues can be reduced to allowable levels by further optimization of this method.

cannabis concentrates

Flash chromatography is a very efficient way to remove pesticides.

Based on the results, we are confident that we will be able to help producers in removing pesticides from cannabis concentrates to make healthy, safe and valuable products.

1 Borel, B. The Wild West of Marijuana Pesticides. The Atlantic [Online]. Aug 31, 2015. https://www.theatlantic.com/health/archive/2015/08/pot-marijuana-pesticide-legalization/401771/ (accessed on Sep 19, 2017).
2 Margolin, M. Cannabis Concentrated Have a Problem With Pesticides. LA Weekly. Feb 27, 2017. http://www.laweekly.com/news/cannabis-concentrates-have-a-problem-with-pesticides-7952469 (accessed on Sep 19, 2017).
3 Bureau of Marijuana Control, Testing Laboratories Initial Statement of Reasons. Bureau of Marijuana Control: bmcr.ca.gov. http://www.bmcr.ca.gov/laws_regs/mcrsa_lab_isor.pdf. (accessed on Sep 19, 2017).

About the author

Leo Zhou

Leo Zhou

Leo was born in Shanghai, China. He has more than 15 year’s experiences on Traditional Chinese Medicine-extraction, purification, and identification. He moved to California at 2013, working with Buchi Corp to support users with machine application. Cannabis process is very similar as Traditional Chinese Medicine, Leo is very happy to use his knowledge and experiences to help this industry.

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