Growing Crystals.

One pretty reliable recrystallization technique involves a mixed solvent system. For this, you will need two solvents of different strength: one that dissolves the molecules easily (Ethyl Acetate) and another that the molecules are mostly insoluble in (Pentane).

Experiment at a small scale.

A good working sample size is around 20-200 mg, and a 20 mL dram vial with a screwcap, or a small round bottom flask with a stopper are ideal. To the evaporated solid sample in the vial, a few mL of pentane are added and then broken up with a stirring rod or metal spatula, ideally sonicated, to produce a fine suspension of the solid. Then, with stirring and/or sonicating, Ethyl Acetate was added one drop at a time until the cloudiness dissipates to a clear, transparent solution. Let the vial sit at room temperature in an undisturbed ventilated area overnight, loosely capped, allowing a slow evaporation to occur. If crystals form in the next few days, they can be collected and washed with cold pentane.

The Layering Method.

If the evaporation leaves behind more of a residue, you can try a layering method. Re-dissolve the sample in the same way that you did before, but before you cap it, using a pipette, add a few mL of pentane slowly and carefully along the side of the vial to make a distinct layer on top. The crystals will form at this layer. Close the cap tightly this time, and let it sit undisturbed in a freezer for a few days. You can try several different ratios of solvent or temperatures. Once you figure out a method that works, you can try that on a larger scale. If your sample is not pure enough for recrystallization, other isolation methods, such a chromatography, may be necessary beforehand.

Contact Us.

If you’re interested in learning more about recrystallization as a method for purifying your extracts, CannaChemist can help. Contact us at info@oriongmp.com and let us help you.

This content is written and supported by Orion GMP Solutions, a pharmaceutical engineering firm dedicated to international standardization of GMP Cannabis.

This might not sound savory to the manufacturing side, but often, there is high variation in the manufacturer’s product.
HempHacker and Orion GMP Solutions firmly believe that testing for product quality is useless when we are talking about GMP Cannabis. It must first be engineered into the product – Quality by Design, to be specific. Testing laboratories serve an important function in the industry. They have many different sample types, and their work must be both accurate and precise.

With multiple sample types (e.g edibles, raw flowers, solid and liquid extracts, and infused beverages), the analytical chemists of the cannabis industry have their work cut out for them. In GMP Cannabis Manufacturing, all the testing is done in-house. This is called in-process testing. In-process testings is an activity that measures your product’s quality attributes as it is being processed.

Several important points come up in these guidelines. When to test. What to test. How to test. These are the essential activities in a GMP Cannabis Testing Facility. In the Cannabis Industry 2.0 (i.e. GMP Cannabis), all laboratory testing will be done in-house, and it will not be hindered by restrictive legislation. Validated and repeatable test methods are mandatory for the analytical laboratory to provide consistent results. This is an important point, should be considered by every cannabis manufacturer.

This might not sound savory to the manufacturing side, but often, there is high variation in the manufacturer’s product. Think about it – how many different structures are there on the plant; how many different light angles are hitting those different structures, how many different samples were taken from the plant… There is a lot to think about, and those are only a few variables.

Take a look at this 36 page PDF developed for New Mexico Cannabis Testing Facilities. It describes everything you would ever want to know about a testing facility down to how they should document their work, to how they actually do their work.

While these guidelines do not explain all aspects of a GMP Cannabis In-Process Testing Laboratory, they do describe the activities well.

Validating SOPs for GMP Cannabis

The objective of validating a procedure is to demonstrate that the procedure is suitable for its intended purpose. This extends to all SOPs. They must be validated to prove that they accomplish their purpose. There are many different processes that can be validated in pharmaceutical operations. Some examples include, but are not limited to, process chemistry, analytical testing, lab facilities, cleaning, equipment, packaging, etc.

For the sake simplicity, this article will cover validation of analytical methods. Method development and validation are all about setting specifications and making sure that the method can reliably achieve those standards. The specifications are discovered during method development, where an analyst works by trial and error to find the right conditions, that are described by example below. It is a tedious process, but once the proper method for analysis is established (i.e. the right column, the right flow rates, the right wavelength, and right temperatures), you have data that should show a reproducible method. From there, it’s a matter of setting the amount of variance that is tolerable to still accomplish the method (i.e. validation parameters).

Analytical method development is the time when the robustness of a method is established. Robust in this sense, means that you can change parameters of the method without seeing variation in the results – that is, despite conditions being less than optimal, you still get good results. Validation checks the variation in methods – you must get the same results for a given method within a specified percentage or relative standard deviation. If a method has been proven to be robust, it has a much greater chance of passing validation (being within the specified variance).

There are three major types of analytical methods: identity tests, assays, and impurity tests. An identity test proves that a certain molecule is present in a sample. An assay shows how much of a molecule is present in a sample. An impurity test shows how much of the sample has degraded or the relative quantities of impurities present in a sample. There are 6 major parameters tested in the validation of analytical methods: accuracy, precision, specificity, detection limits, quantification limits, and range.

Validation parameters require qualified reference standards. Ideally they will be from a third party, manufactured in an ISO environment that ensures the purity. The qualified reference standards are how meaningful comparisons are made to assess each parameter.

  • accuracy – how close to the target value the method reliably achieves
  • precision – how close each measurement is to the other measurements in a series of measurements
  • specificity – identification of the exact molecule that’s being tested – i.e. the method can discriminate between molecules similar to the target molecule.
  • detection limit – the smallest quantity of a molecule that can be detected
  • quantification limit – the smallest quantity of a molecule that can be reliably quantified
  • range – the smallest and largest amount of a molecule that can be reliably quantified in an analytical test

Details of the method should be clearly listed and explained in the validation report. They are important because they clearly lay out the conditions to execute a given method. Here are a few examples of method conditions:

  • Description of the method – e.g. HPLC
  • Type of chromatography column – e.g. C18 Reverse Phase HPLC Column
  • Flow rate and method durations – e.g. 1mL/min – 20 min runtime
  • Detection Wavelength – e.g. 210nm
  • Column Temperature – e.g. 30C

If you have more questions, check out www.oriongmp.com and get a free consultation on putting together your Cannabis related Good Manufacturing Practices and Quality Manufacturing Systems.

https://patents.google.com/patent/US8530679B2/en?q=thc&q=butane&q=cannabis

In 2007, a patent was filed for delta-9 THC processing. It covered a range of organic solvents with boiling points preferably below 0C – ie “low boiling point solvents.” This fits the description of several hydrocarbons – the author preferred isobutylene, propane, butane, and cyclobutane.

This patent was validated with very pure THC – from 95-99% – nearly reagent grade. So while it validates the situation in under perfect laboratory conditions, it does not reflect the true extraction conditions that happen every day for medical and recreational extractions.

The important points of this patent are the temperatures. The desired solvent exists as a gas at room temperature, but can be in the liquid phase when put under pressure and temperature constraints. Controlled temperatures not only dictate the phase of the hydrocarbons (i.e. gas or liquid), but also prevent degradation of cannabinoids, preserve terpenes, and reduce solubility of plant lipids.

Some side notes on the choice of solvents were low toxicity, low environmental impact, and generally recognized as safe for use in pharmaceutical applications. These factors combined are some of the reason for using propane and butane as the industry standard for cannabis extractions.

That covers the theory behind the process. Below you’ll find a few points on the methods that make this a very good process.

Assuming one has an understanding of the standard closed loop extraction process, you can imagine how this process goes. You’ve passed your butane/propane through the extraction column and the extract is sitting in the collection vessel.

It does not specifically say in the patent, but there are two ways this could go. The first option is that the butane is boiled off (reclaimed) to a certain percentage, and then transferred to a secondary container. The second is that the butane is allowed to boil off without care for reclaiming. I find the second option less likely, but it is a possibility.

Assuming the first option, the partially purged extract is transferred to a second collection chamber while it is still of high enough viscosity. This process is called a cannula transfer. The second collection vessel is where there are inert conditions, and the butane/propane is evaporated off.

Solvent is evaporated by increasing the temperature of the second collection vessel and passing inert gas over the surface of the extract – in this case, I’m almost sure the author used a side-arm round bottom flask. I’ve covered the value of inert gasses in a few of my posts at Hemphacker, but it is definitely a standard operating procedure in a chemistry laboratory. In this case, they use argon gas to assist the removal of butane from the extract.

Using inert gas helps remove the solvent by changing the dynamics of partial pressures at the surface of the solution – this is a long topic and out of the scope of this article. However, the change in partial pressure increases the rate of evaporation for butane and allows one to to reduce the temperature to 4C, from what would normally be done at much higher purging temperatures. Now we’re in terpene preservation territory.

The low temperatures are beneficial because it reduces the degradation of the cannabinoids, and also keeps the terpenes in a low-volatility condition. In addition, the author claims that these temperatures make it easier to handle the extract.

As a result of evaporating off propane/butane at a lower temperature, the author claims that the invention induces a more crystalline form of the extract rather than the formation of a homogenous solid. I would hypothesize that the slow cool temperatures allow crystal formation, in what is a more gentle process that does not disrupt the nucleation of seed crystals. They claim to have shown this by x-ray diffraction, but no data is given to supplement the claim. Still, the extract is not 100% crystalline, as claimed by the author; as an analogy, think of how some parts of an extract will auto-butter before others.

One point to keep in mind is that this is a pure starting material, for the sake of explaining the invention of the process. By experience, a chemist performing extractions knows that the results vary by strain to strain, because of the different distribution of cannabinoids and terpenes.

This is a fundamental patent to understand the origins of live resin extractions. This author has several more patents on the subject, but I chose to write about this one because it was the “first mover.” The cannabis community owes much thanks to pioneers in science, who laid the way for us to preserve the ultimate essence of the plant.
I hope that you all find this interesting. Please share your thoughts and comments!

When the extractor has been properly shut down, it’s time to disassemble it and reveal the cannabinoid alchemy you’ve performed, turning solid green plant matter into a concentrated liquid gold $)

Final image - Shut down

Step 7 – Extractor Disassembly – remove stainless steel hose (D) from extractor column valve (1)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 7.1 – Extractor Disassembly – open extractor column valve (1) to allow air to enter extractor
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 7.2 – Extractor Disassembly – remove extraction column (11)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 7.3 – Extractor Disassembly – remove extractor base from extractor collection vessel (12)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx

 

As always, if you have any questions please post them in the comments section. Your questions and time are valuable and we will make every attempt to help you through your process.

Once the extraction collection chamber reaches the desired pressure under vacuum, it’s ready to shut down. Shut down always starts with stopping the flow of butane – i.e. turning off the recovery pump.

Final image - Shut down

Step 6 – Post Recovery Shut Down – turn off the recovery pump (7)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 6.1 – Post Recovery Shut Down – close the recovery cylinder liquid side valve (5)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3xx
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 6.2 – Post Recovery Shut Down – close the purge port (4)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3xx
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 6.3 – Post Recovery Shut Down – close the high pressure recovery manifold (3)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 6.4 – Post Recovery Shut Down – close the extraction column valve (1)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx

 

As always, if you have any questions please post them in the comments section. Your questions and time are valuable and we will make every attempt to help you through your process.

After running the continuous shower, the liquid butane is pulled off into the gas phase by the recovery pump and pushed into the liquid phase, which then fills back into the recovery cylinder. The push/pull method of recovery requires heating the extraction collection vessel (10) and cooling the recovery cylinder (5). The recovery cylinder can be cooled to -50C if you use a dry ice/ethanol bath, but is not necessary – it just speeds up the recovery. Push/pull is governed by the most useful branch of chemistry – thermodynamics – we’ll explain that at a later time if anyone is interested…

Final image - butane recovery

Step 5 – Butane Recovery – heat extraction collection chamber (10) to 85F/30C; cool the recovery cylinder (5) to -4F/-20C; open the purge port (4)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 5.1 – Butane Recovery – open the recovery cylinder liquid side valve (5) and simultaneously turn on the recovery pump (7)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 5.2 – Butane Recovery – open the recovery cylinder liquid side valve (5) and simultaneously turn on the recovery pump (7)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 5.3 – Butane Recovery – recover butane until the pressure gauge reads 10″Hg to 22″Hg
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx

 

As always, if you have any questions please post them in the comments section. Your questions and time are valuable and we will make every attempt to help you through your process.

After the desired amount of time running the continuous shower, the process needs to be shut down. The process can transition directly to the recovery step, but first make sure that no unsafe conditions exist. Since this puts several pounds of butane into the recovery cylinder, the process is inherently dangerous. Take your time and make sure every valve is open or closed as it should be.

Final image - Shut down

Step 4 – Continuous Shower – turn off the recovery pump (7)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 4.1 – Continuous Shower Shutdown – close the low pressure recovery manifold (2)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx

 

As always, if you have any questions please post them in the comments section. Your questions and time are valuable and we will make every attempt to help you through your process.

Continuous showers are the easiest and most efficient way to extract cannabinoids in a CLS. The butane is recycled by being pulled out of the bottom of the collection chamber, in the gas phase. It then passes through the recovery pump, up the the recovery manifold, and is condensed into the liquid phase by keeping the high pressure side of the recovery manifold (3) at ~100PSI.

Final image - Continuous Shower

Step 3 – Continuous Shower – open the high pressure recovery manifold (3)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 3.1 – Continuous Shower – turn on recovery pump (RP) and run the continuous shower for 5-45 minutes – maintain a pressure of ~100 PSI on the high pressure side of the recovery manifold
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx

 

As always, if you have any questions please post them in the comments section. Your questions and time are valuable and we will make every attempt to help you through your process.

Once the extractor has reached maximum vacuum and no leaks have been detected, it can be filled with butane.

Final image - Filling

Step 2 – Fill the extractor – open recovery cylinder liquid side valve
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 2.1 – Fill the extractor – open purge port (4)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 2.2 – Fill the extractor – open the low pressure recovery manifold (2)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 2.3 – Fill the extractor – open the extraction column valve (1) and allow butane to fill the extractor until 45 PSI or the butane stops flowing
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 2.4 – Fill the extractor – when butane stops flowing, close the recovery cylinder liquid side valve (5)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx
Step 2.5 – Fill the extractor – close purge port (4)
Component #Component NameAbbreviationOpen/OnClosed/Off
1Extraction Column ValveECVx
2Low Pressure Recovery ManifoldRM2x
3High Pressure Recovery ManifoldRM3x
4Purge PortPPx
5Recovery CylinderRCx
6Vacuum PumpVPx
7Recovery PumpRPx

 

As always, if you have any questions please post them in the comments section. Your questions and time are valuable and we will make every attempt to help you through your process.