Residual Solvents in Cannabis…and Terpenes with Simon & Garfunkel

By now, a lot of people in the industry know that headspace-gas chromatography (HS-GC) is the ideal analytical technique for analysis of residual solvents in cannabis concentrates, but wouldn’t it be nice to be able to perform another pertinent cannabis analysis on our fancy headspace instrument? It turns out that we can. The beauty of HS-GC is its ability to separate volatile analytes from difficult sample matrices with very little sample preparation. While terpenes are less volatile than residual solvents, all cannabis terpenes (with the exception of phytol) are volatile enough to analyze using HS-GC. With that in mind, we developed a preliminary method for HS-GC analysis of terpenes in cannabis.

In order to keep things as simple as possible, we developed our terpenes method on the Rxi-624Sil MS column, which is the same column that is recommended for residual solvent analysis. Luckily, Jack Cochran had already established that the column does a really good job at resolving terpenes. This means that you can run two different analyses on the same instrumental setup, getting more use out of your instrument investment – hooray! Here’s what the chromatography looks like for a comprehensive set of terpenes:

 

 

Beautiful Terpene Chromatogram

The Rxi-624Sil MS nicely separates a comprehensive set of terpenes.

 

To test out the method sans cannabis, we decided to determine terpene profiles for some of the following common herbs: parsley, sage, rosemary, and thyme (now the title makes sense!):

 

Terpene profiles of common herbs using the Rxi-624Sil MS

Terpene profiles of common herbs using the Rxi-624Sil MS

 

As a disclaimer, this data should be considered semi-quantitative, and the method is preliminary, but our overall profiles matched up well with what we could find about terpene profiles of these herbs. We also profiled hops, which are a close cousin to cannabis.

I will be discussing this and other work at The Emerald Conference in San Francisco on January 23rd. The conference agenda includes some good speakers from the cannabis industry, and it looks like it will be a valuable conference for anyone who can attend. 

2 Responses to “Residual Solvents in Cannabis…and Terpenes with Simon & Garfunkel”

  1. Adam says:

    Hi, great post! just wondering if a GC-FID can have both a headspace autosampler (gas) and a regular autosampler (liquids) or is it either or? Thanks!

  2. Hi Adam,

    Great question! Generally, headspace autosamplers also allow for the installation of a liquid autosampler on the same injection port. For autosamplers with transfer lines (e.g. Tekmar and Agilent), the transfer line plumbs in line with the injection port and doesn’t go on top, so you can install your liquid sampler as you would if the headspace sampler wasn’t there. Just be careful where you put your fittings for plumbing the transfer line – sometimes those fittings are bulky and can interfere with the liquid autosampler sitting on top of the injection port. Other syringe-style autosamplers (e.g. CTC or Gerstel) usually come with the option to do liquid injections as well. You will need a different syringe and vial holder for the autosampler, but they do have the capability to do liquid injections.

    I hope this answers your question, and thank you for commenting!

    Amanda

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