Analytics

How Labs Test for Terpenes

Petar Petrov
Written by Petar Petrov

Measuring a cannabis cultivars’ terpene profile is a big step toward giving consumers more comprehensive information on different products. This in turn helps them make more informed decisions, based on more than the vague “indica vs sativa” distinction.

But as with most big steps, it takes real innovators in their field to take them and to lead by example.

The Fingertip

Analyzing terpenes is no straightforward matter, even by the lofty standards of cannabis science. The challenge arises from terpenes being nonpolar and similar in structure to each other, with many structural isomers existing between them.

Terpenes are volatile (readily turned to vapor), making gas chromatography (GC) ubiquitous for quantifying terpenes. There are two common methods of detection used in GC: flame-ionization detection (FID)and mass spectrometry (MS).

GC/FID

FID can detect lots of phytochemicals, but it doesn’t identify them all. This poses a problem when testing terpenes in cannabis samples. The bewildering abundance of phytochemicals in the flower creates a very large matrix – all the other compounds apart from the analytes which scientists are interested in (the terpenes in this case). The matrix is basically like background noise ora smokescreen amidst which it’s harder for scientists to discern the terpenes of interest. FID is very common, however, due to its price, its predictability, and its ability to successfully evaluate lots of organic compounds.

GC/MS

Although it is more expensive, MS provides increased levels of sensitivity, meaning that very small concentrations can be measured with high accuracy. Also tandem MS can be used to better parcel intricate data from complex matrices. This technique uses, at minimum, three stages of detection (GC-MS-MS), which minimizes the risk of identification errors and misleading results.

The first stage is chromatographic separation by retention time, which refers to the time necessary for a solute to pass through a column.The second stage is the ionization of the separated compounds to measure the molecular parent mass. The third stage is the measurement of daughter/fragment ion masses.

Employing only one of these techniques could leave some room for uncertainty. For example, many terpenes tend to co-elute from a GC column due to similarities in molecular weight and structure. But with those three stages working together, the data obtained give scientists a more complete picture. That said, GC-FID and GC-MS are much more common methods in cannabis laboratories.  It all boils down to how much you want to spend, and what levels of detection and specificity you require.

For a while, terpenes were overlooked while THC and CBD received all the limelight. However, this is changing fast, with more curious eyes falling on terpenes’ multi-dimensional properties. This surge in interest wouldn’t be possible without many labs’ consistent efforts to refine the complex and arduous process of quantifying a comprehensive terpene profile.

Image Credits: Freedom Leaf

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Petar Petrov

Petar Petrov

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