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Analysis of Terpenes in Cannabis: Methods of Measurement

The unique aroma of your favorite CBD flowers as well as the different effects they can elicit are largely determined by the terpenes. With the increasing legalization of marijuana in many countries, the cannabis sector has modernized. Today’s customers are looking not only for the potency in THC and CBD but also specific terpene profiles, which has increased the demand for terpene analysis in laboratories. Here I will tell you about some ways to measure these terpenes and some more curiosities about these compounds.

Introduction to terpene analysis

What is terpene analysis?

Terpene analysis are methods by which the amount of terpenes in a sample is quantified. This analysis is crucial to determine the sensory and therapeutic properties of plants, especially in the case of Cannabis sativa.

Since it is possible that all of these compounds are acting in unison to produce a particular effect in cannabis, it is important to know which compounds are being consumed. For this reason, terpene analysis is an increasingly requested service in laboratories.

What are terpenes and how are they classified?

The terpenes are volatile organic compounds that contribute to the aroma and flavor of very many plants [7], including the marijuana plant, and are the basis of many essential oils used in food or in the production of cosmetics [8], for example.

It appears that terpenes may have therapeutic properties, including anti-inflammatory, anticancer, antiseptic, astringent, analgesic, antidepressant, antimicrobial, antidepressant, and digestive properties [1-6]. In particular, terpenes in the Cannabis sativa plant not only define the sensory properties of cannabis buds, but may also influence their therapeutic properties [7].

Terpenes are derived from various combinations of isoprene units, an aromatic organic compound of five carbon atoms (C5). The classification of terpenes depends on the number of carbon atoms: monoterpenes have ten carbons (C10), sesquiterpenes have fifteen (C15) and diterpenes have twenty (C20) [7].

How does terpene analysis help in the quality control of cannabis?

A high quality cannabis sample should have terpene diversity. When the aroma of the terpenes has been lost, it is possible that the sample is old or has not been cultivated in a proper way.

Terpenes in Cannabis sativa

Terpene Diversity in Cannabis sativa

In the marijuana plant, terpenes constitute one of the major phenotypic diversities and about 150-200 distinct terpenes have been reported in cannabis, mostly monoterpenes and sesquiterpenes [8, 9].

Most common terpenes in Cannabis sativa

In marijuana-type Cannabis sativa available in dispensaries in the U.S., the most common terpenes are beta-myrcene and limonene both monoterpenes, and beta-caryophyllene which is a sesquiterpene [10].

Importance of terpenes in cannabis

Due to their properties, terpenes contribute to the smoking experience by providing specific aromatic profiles, as well as possible effects on the organism. These aromatic compounds are capable of interacting with cannabinoids. cannabinoids and enhance their effects. They may also interact with other terpenes present in the plant. This phenomenon, known as the entourage effect increases the therapeutic benefits of cannabis.

Some cannabis terpenes are associated with specific effects. The “sativa effect“, for example, is popularly used for strains that produce energizing and uplifting effects. These may contain terpenes such as limonene and pinene, which have a fresh citrus aroma. The “indica effect” varieties may contain more myrcene, a terpene with an earthy aroma and which is associated with relaxing and calming effects. If you want to go deeper, check out the post about the differences between indica and sativa .

Methods of analysis of terpenes

The most commonly used method of analysis for measuring terpenes is gas chromatography, which can be coupled with mass spectrometry to obtain more accurate results.

There is also the SPME technique and the VASE. Given the high volatility of terpenes, gas chromatography is one of the most commonly used techniques for their determination.

Gas chromatography: The most widely used method to measure terpenes.

Gas chromatography (GC) is the most commonly used way to measure terpenes. This technique is also used for the analysis of analysis of cannabinoids . It consists of a gas as mobile phase and it is necessary to heat the sample to homogenize it.

Gas chromatography, schematic
Gas chromatography, schematic

How gas chromatography is performed

Sample preparation:

The process starts with the preparation of the sample in a suitable form to be inserted into the gas chromatograph.

Sample injection:

Once prepared, the sample is injected into the machine, which applies heat to vaporize it.

Separation of components:

The vaporized sample is carried through a column by an inert gas, which acts as a mobile phase. The column, which contains a stationary phase, interacts with the sample components in different ways, causing them to separate at different rates.

Detection and quantification:

As the components exit the column, they are detected and analyzed by a computer. These data are recorded and plotted on a graph called a chromatogram.

Chromatogram interpretation:

The graph shows the detected signals versus time. Each peak in the chromatogram represents a different component in the sample. In the example at hand, each peak is a terpene (sample component).

Identification of the components:

To identify terpenes in the sample, the retention times (the time it takes for each component to pass through the column and reach the detector) are compared with the retention times of other known substances (such as terpenes).

The combination of gas chromatography-mass spectrophotometry (GC-MS) and gas chromatography-mass spectrophotometry (GC-MS)

Gas chromatography can be coupled with mass spectrophotometry (MS), which is a technique where the weight of individual compounds is determined. This combination, abbreviated as GC-MS, is quite accurate for measuring both cannabinoids and terpenes.

In this process, after the terpenes are separated by GC, they are fragmented and analyzed by MS according to their mass-to-charge ratio. This provides additional information that can help confirm the identity of the terpenes in the sample.

In this way, it is possible to identify and quantify quite accurately the terpenes in a cannabis sample, which can be of great use to producers and consumers seeking to understand and control the terpene profile of their products.

Alternatives to gas chromatography: HS-SPME and VASE

There are other techniques used to measure terpenes. One of them isHeadspace-Solid Phase Microextraction ( HS-SPME), which is a method that does not require the use of solvents. Headspace refers to the gas layer above a sample in a vial, and this is analyzed rather than the volume below where the sample is located.

Therefore, HS-SPME is used on volatile samples such as those with benzene, toluene, and xylenes [8]. HS-SPME has an advantage in that sampling, extraction and concentration measurement can be done in a single step [7].

As terpenes are volatile, some of the techniques for measuring them do not make use of solvents or measure the void space instead of the compound.

Vacuum Assisted Sorbent Extraction( VASE) is based on the use of a sorbent in the headspace that has been exposed for a certain time to the inflorescence of the plant.

This inflorescence is heated to 100°C at a pressure of 0.36 atm. There are several techniques where the headspace is analyzed, but the VASE technique guarantees an exhaustive extraction given the large amount of absorbent material [7].

Important considerations in terpene evaluation

It is important to standardize methodologies for assessing the composition of Cannabis sativa inflorescences and extraction protocols. A good understanding of these protocols and methodologies is crucial, as those that pre-heat the flower may degrade or evaporate the terpenes prior to analysis, altering the result [7].

Given the volatility of terpenes, when the flower is heated to decarboxylate the cannabinoids, the cannabinoids are decarboxylate the cannabinoids the terpenes are degraded or evaporated.

When seeking to decarboxylate cannabinoids a problem occurs, as heating modifies the terpene profile [7]. For this reason, it is recommended not to preheat, and thus obtain products high in terpenes [7, 11].

Home extraction of cannabis terpenes

One of the solvents for terpene extraction that seems to work very well is olive oil, since it allows the solubilization of terpenes avoiding their evaporation.

* You may be interested in: Homemade Cannabis Extractions

Mysteries and curiosities of terpenes in Cannabis sativa

And well, last time I left you with an unknown that we now have a little more information about. The ecological reason why the Cannabis sativa plant produces all these compounds is still unclear, but apparently terpenes are a defense mechanism [12, 13]. So, if the plant is grown in places where it requires protection, it would produce more of these compounds. A recent study suggests that when the plant is grown outdoors, it produces more terpenes than when grown indoors [14]. These preliminary results indicate that the phenotypic expression of these terpenes in Cannabis sativa appears to be highly dependent on the environment and may differ between two plants of the same variety grown under different environmental conditions [14].

Well, I look forward to trying some of your extractions with olive oil full of terpenes. Let me know how it goes!

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  10. Smith, C.J., et al., The Phytochemical Diversity of Commercial Cannabis in the United States. bioRxiv, 2021.
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Dra. Daniela Vergara
Investigadora y catedrática | Especialista en cultivos emergentes y consultora de cannabis

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