Story by Michael Hagar
Of all the topics within in the cannabis industry, none are more interesting than cannabis analysis and quality assurance.
Included in this category is testing for potency, residual solvent, moisture levels, microbial screening, among others, These tests are important to medicinal and recreational marijuana users alike.
Thus far no cases have been reported of cannabis use leading to cancer; in fact, a growing body of evidence suggests the opposite. However, without proper regulation and testing for pesticides, that may not always be the case. A problem that has been reported is instances of cannabis products being sold that contain only a fraction of the cannabinoids their labels promised. Another area related to quality, particularly in areas like the Pacific Northwest, is mold and mildew, which remain constant threats to growers. Accidental exposure to certain molds or the unknown ingestion of banned pesticides can result in health complications. For these reasons and more, the science and practice of cannabis testing is very important.
The following is the author’s interpretation of different cannabis testing methods and the equipment required to perform them. This information comes from knowledge acquired by visiting labs and by reading various supportive materials.
Thin Layer Chromatography
Thin layer chromatography (TLC) is an analytical method used to detect cannabinoids and other analytes.
For those new to this topic, an analyte is defined as “a chemical substance that is the subject of chemical analysis.” In the context of cannabis, this could be anything from delta-9-THC to a specific pesticide such as myclobutanil. TLC can identify various compounds found throughout cannabis and cannabis-containing products, but this method of testing usually can’t provide accurate cannabinoid concentration levels. An improved and more accurate version of TLC is called “high-performance thin layer chromatography” (HPTLC). Though useful as a tool in various cases related to cannabis analysis, both of these methods are outperformed by the more accurate, capable, and peer-reviewed testing method of high-performance liquid chromatography (discussed below).
Current cannabis labs are unlikely to useTLC or HPTLC for analytical testing. However, a company called Alpha-CAT sells test kits using these methods, which can provide accurate qualitative analysis of CBD, CBN, THCV, CBG and CBC. Alpha-CAT tests require only 0.1 grams of sample material, can be used to generate strain profiles and can be handled by anyone capable of following proper safety precautions. Rough quantitative analysis can be performed by a trained technician with Alpha-CAT tests, but for truly accurate results labs prefer to HPLC and GC/MS instruments.
High Performance Liquid Chromatography
Formerly known as high-pressure liquid chromatography, high-performance liquid chromatography (HPLC) is a technology that can qualify and quantify the various cannabinoids found throughout cannabis samples. This method of testing is capable of quantifying the inactivated or acidic forms of THC, CBD, etc. and is the de facto tool of choice for performing potency tests.
HPLCs are incredibly sensitive, and require calibration and heavy dilution of sample materials before testing. Samples typically end up in 1ml vials before either manual or automatic injection into the HPLC solvent stream. Different labs use different solvents, but ethanol and methanol are the most common. The solvent stream and sample material are moved into what is known as the “column.” Different compounds in the column pass through and elude (leave) at different times, which causes separation, allowing passage into a detector of choice and final identification.
Some labs use ultraviolet detectors to generate the elution profile. but HPLC can also be used with diode array detectors (DAD), mass spectrometers (MS) and even electrochemical detection (ECD) devices for situationally tailored needs. OlderHPLC units can be found on the market for as low as $10,000, while modern units from Shimadzu can cost over $30,000. Another kind of HPLC technology, called ultra-high performance liquid chromatography (UHPLC), incorporates the same principles as its younger counterpart but can be run at much higher pressures, thus providing a higher level of resolution and faster runtimes.
As many of you already may know, cannabis concentrates are often made with a hydrocarbon gas such n-butane and propane or with a solvent such as ethanol or hexane. If crafted and purged properly with heat and/or by using a vacuum chamber, these concentrates should have very little residual solvents left in them. In order to determine residual solvent levels, which are measured in parts per million (ppm), labs use what is known as gas chromatography (GC). Gas chromatographs use a much longer column than an HPLC and apply heat to the sample material in a method similar to fractional distillation. GC units are often used with a flame ionization detector (GC/FID) and even a mass spectrometer (GC/MS) to detect a significant number of pesticides. Modern GC/MS setups can cost about $200,000 and be made highly efficient and automated by headspace autosamplers.
As mentioned previously, because gas chromatography requires applying heat to a sample, it is not readily capable of measuring the naturally occurring acidic forms of cannabinoids. There is a way in which acidic form values of cannabinoids can be determined with GC methods. The process is known as derivatization but, for the sake of simplicity, most labs stick to using HPLC. That being said, gas chromatography can be used for potency-testing edibles or other products that will be heated prior to consumption, and while useful for terpene profiling, it should not be used for testing live resins, flowers, etc.
Depending on the task at hand, ultraviolet and diode array detectors may not be the right tool for the job. In order to achieve a higher degree of accuracy and precision, mass spectrometers sometimes are used in tandem with liquid and gas chromatography. HPLCs and GCs that incorporate a mass spectrometer-style detector are referred to as a LC/MS and GC/MS systems. The topic of mass spectrometry is incredibly technical and requires a firm grasp on multiple sciences to truly understand, but here is a short explanation on how it works:
The components of a sample are separated and prepared with an HPLC or GC. Instead of being run through an ultraviolet detector or an FID, the solid, liquid, or gas sample is passed into an ionizer. Operating in a vacuum, this component bombards the sample with electrons, causing it to become positively charged, or ionized. The ionized sample constituents are next accelerated through a negatively charged electrical field and passed by a magnet that is contained within the mass analyzer. The path of the ions will be bent by the magnet according to their mass-to-charge ratio. (The heavier particles will be more attracted to the magnet than the lighter ones.).
The next step is passage through an “electron multiplier.” When an ion hits the first plate contained in the electron multiplier it causes a chain reaction. The first plate generates electrons from the collision point, which collide with the next plate. The process is repeated from plate to plate until it yields an amplifiable signal. This signal is passed to the last component, the amplifier, and is then sent to a computer where they can be interpreted.
MRX Labs in Tigard, Oregon, has acquired a highly advanced mass spectrometer known as a triple quadrupole mass-spectrometer attached to an UHPLC. This setup is known as LC-MS/MS. It is incredibly sensitive, costs about half a million dollars and is capable of rapidly performing pesticide testing. With an instrument like this, MRX Labs is able to test for the 70 pesticides required in Oregon in only 10 minutes. Apparently, only two of these units are housed in the state of Oregon: one at MRX Labs and the other unit at Oregon Health Sciences University (OHSU).
Properly drying cannabis is a crucial step in the production process. Excess moisture can create a breeding ground for bacteria and other unwanted microbes. Optimum moisture levels can vary according to personal preference, but content should typically be between six and 12 percent. Any higher, and the risk of contamination is dramatically increased. Even after proper drying, certain molds and fungi can become problematic during the storage process if not managed properly.
When a sample is brought in for potency testing, the lab typically performs moisture analysis by using a convection oven. The dry and wet weights of the sample are recorded and the total moisture loss is calculated for the final report. This process can take up to 24 hours to properly complete, depending on the outcome required by state regulation. Moisture analysis is a key component in recreational and medicinal cannabis potency tests to help maintain high levels of quality and safety.
Microbes are everywhere in the environment. If a cannabis sample was sent to space and back it would still harbor some form of life. A microbial screening result of zero colony-forming units per gram, or CFU/g, would be worth investigating, because ofit is highly unlikely to happen. Microbes include yeasts, molds, and bacteria, among others. Some are harmless and generally safe, while others are harmful to varying degrees. For example, accidentally ingesting mycotoxins produced by aspergillus can cause adverse effects, including death. Because many medicinal marijuana patients have compromised immune systems, forgoing microbial screening is never recommended—even if not required by law.
In order to identify these potentially dangerous critters, cannabis testing laboratories typically use a technique known as “plating.” The first step in the plating process is to washcannabis samples with a buffer solution. A small amount of that buffer solution is then placed in a petri dish containing agar and nutrients. Organisms contained within the dish are allowed to incubate for 48 hours or more so they can be identified and quantified. The CFU/g cut-off value depends on whether a product is a flower, tincture, edible, etc. and the kinds of microbes for which it is being tested.
Agar plating is a widely used and peer-reviewed technique for microbiological screening, but for customers who want faster turnaround times, another analytical method available is known as quantitative or real-time polymerase chain reaction (qPCR). This technique is more sensitive than plating and can be completed within hours instead of days; but it also requires purchasing some extra lab gear. Another benefit of using qPCR is that more microbial contaminants can be detected than by plating and it also allows for determination of cannabis strain lineage.
Pesticide use and screening in both recreational medicinal cannabis industries have been of growing concern in the past few years. Steep Hill Labs, a leader in the cannabis testing industry, summarizes the current pesticide problem perfectly on their website. They state:, “There is little known about the sources, growing and curing conditions, or pesticide use for cannabis currently available for purchase. While many growers and collective dispensaries take care to provide safe, effective products, there are numerous reports of the presence of pesticides in purchased cannabis. Due to cannabis’ federal legal status, no pesticide residual tolerance limits have been established by the EPA; however, some medical cannabis states and some legal markets have outlawed the use of pesticides with cannabis.”
Some states, such as Washington, Oregon and Nevada, have adopted legislation that requires pesticide screening, in the interest of medicinal and recreational cannabis consumers alike. The cost of these tests vary depending on the laboratory, as well as the number of pesticides for which they are screening..
The latest information available shows Confidence Analytics in Washington charging $250 for I-502 compliant pesticide screening and Rose City Labs in Oregon pricing their GC/MS based pesticide screening at $70 per sample. In order to detect all required and optional pesticides, labs will typically have to use both LC/MS and GC/MS machines. By using both machines, labs increase their chances of picking up unknown materials, as well.
The Emerald Test
The possibility for error always remains when having cannabis tested, despite expensive, high-quality equipment, highly qualified staff, and passing required inspections. To lessen the chance of error, seek out a lab that has performed well on “The Emerald Test. The Emerald Test is a biannual inter-laboratory comparison and proficiency test (ILC/PT) that is organized by Emerald Scientific, a world leader in high-quality analytical lab gear and services. The test is used to measure the accuracy and proficiency of cannabis testing laboratories across the country. Laboratories can enroll during select times prior to the events and the results are used to create industry benchmarks and to help state regulatory bodies make decisions regarding certification programs.
Here’s how it works: First, the Emerald Test Advisory Board decides which compounds will be included in potency test samples and at what concentration levels. Test samples are then generated by an ISO 17043-accredited manufacturer and are shipped overnight to participating labs so they can be analyzed. The test results are submitted through a secure electronic data portal and are then evaluated by the American Oil Chemists Society (AOCS). If the results fall within +/-1 of the collective statistical average, or z-score, the lab is awarded an Emerald Badge. This badge can be displayed by the laboratory for a full year, to show customers that the lab’s test results are scientifically verifiable and accurate. For more information about The Emerald Test, including which labs have participated, how to order individual potency or residual solvent tests, and more please visit the official website at www.theemeraldtest.com/
• Prices for medicinal and recreational cannabis testing and methods will vary depending on a number of factors including location, compliance to state regulations, etc. When shopping around for cannabis testing services, try these three useful tips:.
• Remember that no matter how expensive a particular machine is, without proper calibration and a knowledgeable operator, test results may differ significantly from reality.
• Make sure that your lab of choice has qualified employees, adheres to state regulations, uses proper peer reviewed testing methods, is transparent with customers and remember look for the Emerald Badge seal of approval.
• Keep in mind that the cannabis testing industry is still in its nascent form and will be rapidly evolving in the months and years to come. This is only the beginning.