Tag Archives: vacuum

Solvent Remediation – The Last Step for Safe, Clean Hemp Extraction

By Tom Bisbee
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Botanical extraction is not specific to cannabis and hemp, and it is anything but new. Rudimentary forms of plant extraction have existed throughout history and evolved with high-tech equipment and scientific procedures for use in pharmaceuticals, dietary supplements and botanicals.

In food production, examples of hydrocarbon extraction processes are commonplace. Nut, olive and vegetable oil production use solvents to extract the oils. Decaffeinated coffee uses hydrocarbon extraction to remediate the caffeine, and making sugar from beets, or beer from hops, also requires solvents.

As such, the FDA has set guidelines for the amount of residual solvents considered safe for consumers to ingest. Yet, without FDA guidance in cannabis and hemp, many products aren’t being tested against these standards, and consumers will ultimately pay the price.

Understanding solvent remediation technology and processes

If we use ethanol extraction as an example, the extraction process is relatively simple. First, we soak the biomass in denatured or food-grade ethanol, ending up with a final solution that is 90-95% solvent. Then, we perform a bulk removal of the solvents, which takes out most, but not all, of the solvent. The next and final step should be to strip the remaining solvents from the extract entirely.

Stripping remaining solvents in bulk requires the right equipment.

But, in order to do so effectively, you need the right equipment, and unfortunately, this is where many producers fall short. Many producers use a vacuum oven to apply heat while reducing the headspace pressure to lower the solvent’s boiling point and evaporate it off.

However, it’s a static environment in a vacuum oven, which means the material is stagnant. So, the process may effectively remove the solvents close to the surface, but solvents deep inside the material tend to get trapped without some type of agitation or mixing.

The appropriate final step to complete solvent remediation is wipe-film distillation, which feeds small volumes into a column, which is then wiped into a very thin film and heated under vacuum pressure. Although the equipment necessary is costly, this last step removes any residual solvents from the product to create a safe, effective and consumable product.

Residual solvents present huge risks

As stated, many of the same solvents used in cannabis and hemp extraction have been considered safe in food production for decades. Reviewing chemical data sheets, many of the acceptable limits on solvents were determined for ingestion, which is fine for edibles and tinctures, but many cannabis and hemp products are intended for inhalation or vaporization.

Just a few of the dozens of various products types on the market today, extracted with a variety of different solvents

Unfortunately, some solvents can have negative health impacts, especially for those using cannabis or hemp for medical purposes or with compromised immune systems. Plus, as a therapeutic and recreational substance, consumers may be consuming more than the recommended amount, as well as using the products several times a day. Unfortunately, long-term exposure or repeated inhalation of these residual solvents hasn’t been thoroughly researched.

For example, inhaling ethyl alcohol (ethanol) can irritate the nose, throat and lungs. Extended exposure can cause headaches, drowsiness, nausea, vomiting and unconsciousness. Repeated exposure can affect the liver and nervous system.

In the food industry, hexane is approved for extracting spices or hops, and this solvent is widely used in cannabis and hemp extraction. However, if used in an inhalable product, chronic exposure to hexane could be detrimental, with symptoms including numbness in the extremities, weakness, vision problems and fatigue.

Consumers deserve transparency

In the industry’s earliest days, companies were tight-lipped about their processes, the chemicals they used and how they removed them. Everyone thought they had the “secret sauce” and didn’t want to share their approach. Today, companies are more open about what they use, how they process it and providing that necessary transparency.

Lack of quality and consistent regulations in these industries creates confusion for the consumers and loopholes for producers. Some producers test for everything under the sun, and some producers know exactly which labs will pass their products, regardless of test results.

While the regulatory bodies are distracted by the amount of THC that might linger in products, getting sick is overshadowed by the risk of getting high. In the meantime, consumers are left to their own devices to determine which products are safe and which are not.

Although testing mandates and regulations will help clean up the industry, until then, consumers need to demand full-panel COAs that not only show cannabinoid potency but also accurately display the test results for residual solvents, pesticides and heavy metals.

Dr. Ed Askew
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Distillation Of Your Cannabis Extract: Ignorance Is Not Bliss

By Dr. Edward F. Askew
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Dr. Ed Askew

In a previous article I discussed the elephant in the room for clients of laboratory services- the possibility of errors, inaccurate testing and dishonesty.

Now, I will explain how the current “smoke and mirrors” of distillation claims are impacting the cannabis industry in the recreational and medical areas. We have all heard the saying, “ignorance is bliss.” But, the ignorance of how distillation really works is creating misinformation and misleading consumers.

That is, just because a cannabis extract has been distilled, doesn’t mean it is safer.There have been reports of people claiming that “Distilled cannabis productsthat are Category 2 distillate are pesticide free and phosphate free, while Category 1 has pesticides and phosphates, but within acceptable limits”

The problem is that these claims of Category 1 and Category 2 cannot be proven just by saying they are distilled. Ignorance of the physical chemistry rules of distillation will lead to increased concentrations of pesticides and other organic contaminants in the supposedly purified cannabis distillate. That is, just because a cannabis extract has been distilled, doesn’t mean it is safer.

So, let’s look at a basic physical chemistry explanation of the cannabis distillation process.

  • First off, you must have an extract to distill. This extract is produced by butane, carbon dioxide or ethanol extraction of cannabis botanical raw material. This extract is a tarry or waxy solid. It contains cannabinoids, terpenes and other botanical chemicals. It will also contain pesticides, organic chemicals and inorganic chemicals present in the raw material. The extraction process will concentrate all of these chemical compounds in the final extract.
  • Now you are ready to distill the extract. The extract is transferred to the vacuum distillation vessel. Vacuum distillation is typically used so as to prevent the decomposition of the cannabinoid products by thermal reactions or oxidation. Under a vacuum, the cannabinoids turn into a vapor at a lower temperature and oxygen is limited.
  • Part of the vacuum distillation apparatus is the distillation column. The dimensions of this column (length and width) along with the packing or design (theoretical plates) will determine the efficiency of distillation separation of each chemical compound. What this means is that the more theoretical plates in a column, the purer the chemical compound in the distillate. (e.g. Vigreux column = 2-5 theoretical plates, Oldershaw column = 10-15 plates, Sieve plate column = any number you can pay for).
  • The temperature and vacuum controls must be adjustable and accurate for all parts of the distillation apparatus. Failure to control the temperature and vacuum on any part to the apparatus will lead to:
    • Thermal destruction of the distillate
    • Oxidation of the distillate
    • Impure distillate

Now, you can see that a proper distillation apparatus is not something you throw together from a high school chemistry lab. But just having the proper equipment will not produce a pure cannabis product. The physical chemistry that takes place in any distillation is the percentage a chemical compound that occurs in the vapor phase compared to the percentage in liquid phase.So, how can you produce a cannabis distillate that is clean and pure?

For example, let’s look at whiskey distillation. In a simple pot still, alcohol is distilled over with some water to produce a mixture that is 25%-30% ethanol. Transferring this distillate to an additional series of pot stills concentrates this alcohol solution to a higher concentration of 85%-90% ethanol. So, each pot still is like a single theoretical plate in a distillation column.

But, if there are any chemical compounds that are soluble in the vapor produced, they will also be carried over with the vapor during distillation. This means that pesticides or other contaminants that are present in the cannabis extract can be carried over during distillation!

So, how can you produce a cannabis distillate that is clean and pure?

  • Produce a cannabis extract that has lower concentrations of bad chemicals. Since a lot of the cannabis extracts available for distillation are coming from grey-black market cannabis, the chances of contamination are high. So, the first thing to do is to set up an extraction cleanup procedure.
    • An example of this is to wash the raw extract to remove inorganic phosphates. Then recrystallize the washed extract to remove some of the pesticides.
  • Make sure that the distillation apparatus is set up to have proper temperature and vacuum controls. This will limit production of cannabis decomposition products in the final distillate.
  • Make sure your distillation apparatus has more than enough theoretical plates. This will make sure that your cannabis distillate has the purity needed.
  • Finally, make sure that the staff that operates the cannabis distillation processes are well trained and have the experience and knowledge to understand their work.

Inexperienced or under-trained individuals will produce inferior and contaminated product. Additional information of extract cleanup and effective vacuum distillation can be obtained by contacting the author.