Tim Youngblood   |   October 03, 2017

Cannabis Testing for Potency and Terpenes

Learn the basics of gas and liquid chromatography and FTIR Spectroscopy for testing terpenes and potency within a strain.
Tim is a technology journalist and was an editor for All About Circuits. His specialty as a historian at Boise State University was cannabis legislation. His favorite things to write and nerd out about are experimental technology, single…

Learn the basics of gas and liquid chromatography and FTIR Spectroscopy for testing terpenes and potency within a strain.

What is Gas Chromatography?

Gas chromatography is a subgroup of mass spectrometry. It is a group of separation techniques that are used to analyze volatile substances in their gas phase. In gas chromatography, the components of a sample are dissolved using a solvent and vaporized in order to separate the analytes by distributing the sample between two phases: a stationary phase and a mobile phase. The mobile phase is a chemically inert gas that serves to carry the analyte's molecules through a heated column. Gas chromatography is one of the few forms of chromatography that does not utilize the mobile phase to interact with the analyte.

For cannabis, gas chromatography is used to test samples for potency and efficacy. In this context, potency refers to the ratio of common cannabinoids such as THC, CBD, as well as terpenes, which give cannabis strains their flavors and smells. Terpenes also have their own medical and psychoactive properties but compared to the study of cannabinoids, terpene research for cannabis is still in its infancy. With gas chromatography, growers can view the levels of various cannabinoids and terpenes to determine the effects of a strain in order to determine the best application or market for a strain. In the case of medical cannabis, gas chromatography helps to determine which symptoms a strain is best suited to treat. In the case of recreational cannabis, gas chromatography helps to determine the user's experience, which is often categorized by ratios of Indica and Sativa.

 

What is Liquid Chromatography?

Liquid chromatography is a technique used to separate a sample into individual parts. This separation occurs based on the interactions of the sample with the mobile and stationary phases. Because there are many stationary/mobile phase combinations that can be employed when separating a mixture, there are several different types of chromatography that are classified based on the physical states of those phases. Liquid is used to carry the sample through the spectrometer because of its ability to separate individual sections of a sample as a solvent.

Liquid and gas chromatography are both used to test strains for potency and efficacy. The differentiator between the two is the physical state of the substance used to carry samples through the spectrometer. 

 

Intuvo 9000 GC for Potency and Terpene Testing

This model made by Agilent Technologies is a gas chromatograph system (That's what the GC stands for) that was designed to be small and easy to use. The unit uses a touchscreen interface and is smaller than most GC systems on the market. This device is used to test the potency of strains and identify terpenes.

 

Datasheet (PDF)

 

1290 Infinity II LC for Terpene Testing

This model is a UHPLC, which stands for ultra-high performance liquid chromatography. While I personally cringe at the use of a phrase like "ultra high performance" in scientific terminology, the term is technically accurate and was not coined by the device's manufacturer, Agilent. A UHPLC is essentially a liquid chromatography (LC) system that uses smaller samples than most LC systems and can process results faster. The sensitivity of these LC systems make them well suited for testing terpenes.

UHPLC's are not without their own set of drawbacks, however. Because smaller particle samples are used, more care has to be taken during preparation in order to ensure that the samples are not contaminated. UHPLC's are fast and efficient but require an experienced operator.

 

Datasheet (PDF)

 

Cary 630 FTIR Spectrometer for Potency and Terpenes

FTIR stands for Fourier-transform infrared spectroscopy. Fourier transform is the process of decomposing a signal into the frequencies that combine to make that signal. The process is similar to taking a musical chord and separating it into the individual notes that comprise it. In the case of FTIR, the signal that goes through the Fourier transform process is the sample being exposed to infrared light. Most molecules are "infrared active", which means that they react in various ways when exposed to infrared light. FTIR systems can test samples that are in solid, gas, or liquid states.

In the case of cannabis, FTIR systems are used to find optimum ratios and schedules for lighting and watering in order to maximize potency (PDF). An FTIR system can also test strain samples in different physicals states. This allows growers to see the composition of cannabinoids and terpenes in solid and gas form. Many cannabinoids and terpenes have different decarboxylation points, which means that some methods of consumption can be better than others for different strains. Choosing between smoking, vaporizing, eating, skin exposure or even drinking as an optimum form of consumption will vary based on the composition and desired application of strain. An FTIR system can help growers determine the best proverbial "package for their product".

This particular model has a small central unit (About the size of a small toaster) that has different attachments based on the matter states of samples.

 

Datasheet (PDF)

 

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