GC/MS Testing – What It Tells You, and What Some Companies Don’t Want You To Know

GC/MS Testing - What it REALLY Says About Essential Oil


Most companies advertise that their oils have been “GC/MS Tested”. What is this testing? What does it tell you about your oils? Is it enough for the company to publish test results? Let’s take a look…

What Even is GC/MS? I’m Not a Scientist!

“GC/MS”, when used in this context, stands for Gas Chromatography and Mass Spectrometry. And I’m guessing that if you’re reading this, that still doesn’t mean anything. It’s OK, it didn’t mean anything to me when I first started, either. For those of you who watch shows like “NCIS” or “CSI”, you’ve probably heard these tests and machines mentioned. In most modern labs, the two tests/machines are used together, to produce a full result. We’re going to talk in super-simplified terms and methods, so if you’re looking for serious specifics or words from a scientist, this isn’t your article. If you just want to know a little about this stuff so you feel more like you know what people are talking abut, here you go:

Gas Chromatography

A gas chromatograph is a machine that separates the components of a substance so that those components can be charted. In this case, we’re talking about oils, so I’m going to stick with those terms and processes. The technician adds a bit of the oil to a container filled with inert gas. The gas is heated, and carries the oil/gas vapors through a tube. If you now how steam-distilled oils are created, picture that, only with an inert gas rather than steam to carry the oils. The compounds in the oil “fall out” of the gas as they cool, and are collected on the sides of a glass tube in the machine. Remember, we’re talking about individual ions now – microscopic particles, not drops. The rate at which these components vaporize and their perceived “weight” are measured. The measuring happens with…


Mass Spectrometry

This one is even more complex. Once the particles of oil have been ionized during gas chromatography, the mass spectrometer uses the charge of the ions to discover what the substances could be. It tests against known compounds, to sort even slight differences between individual elemental parts. This is where your high school chemistry comes in, if you had a good class. And if it hasn’t been way too long to remember.

Elements have mass and electrical charge. This charge dictates how or how well the elements bond, or combine with other elements. Spectrometry looks at each of those ions and,  “knowing” how they combine, calculates how much of what is in the sample, based on their mass. This is called a “mass spectrum”. Again, this is simplistic, but for our purposes, the basics are important, the specifics are not. If you’re interested, start here for a deeper dive.


What Do The Results Tell the Technician?

The skilled, knowledgeable operator of these machines uses a set of possible output options. In other words, the machine is testing for the compounds it is asked to look for. It gives information on which of the compounds were discovered, and in what concentrations. If the machine and technician pick up a compound that they were not trying to find, the result will show as “unknown”. In some cases, a technician will be able to check a few other options, but we’re talking about basic testing, not solving a murder. They run the test and move on to the next job. Because that’s their job, and I’m grateful they do it.

These results are frequently in the form of a chart. It shows each compound and the concentration in which it occurs in the sample. On these charts, you may see results like “Menthol, 50.4”. This means 50.4 percent of the oil tested was the compound we call “menthol”.


What Do The Results NOT Tell the Technician?

They can’t find what they’re not looking to find. If a technician isn’t looking for 1,8 cineole, the testing is going to show quite a bit of unknown product when they test peppermint. That’s why it takes a skilled technician to work the machines. Or it’s one of many reasons, anyway. They need to have some idea what it is they’re looking for!

The results also do not tell the technician how the components or compounds got into the bottle. While they are detectives inside the lab, it is not their job to watch your oil be produced from growth through harvesting and processing. They test what they are given, the same as you work with the resources you have at whatever you do. The technician may not know “natural” compounds from those extracted or created in the lab next door. If all the chemicals line up and bond properly, they are chemically the same thing. My mom talks about how my grandfather, both naturalist and chemist, told her often:  a created compound and a naturally-occurring compound look exactly the same when you see them on a microscopic level.


What Do The Results Tell YOU?

Ah, the good stuff. GC/MS results tell you how your essential oils work to help you body! Certain chemicals react with your brain, endocrine system, and other body systems, and a graph telling you which chemicals are in your bottle can be crazy helpful! Want to add some wintergreen to your muscle-soreness topical blend? A GC/MS result can tell you exactly how much thojune (the medicinal but toxic compound) is in your oil, so you can use the best dilution rate for your needs. If a plant is supposed to have a high percentage of limonene, but the results don’t show it, that’s a tip that your orange or lemon oil might not be of the highest quality. This can happen to even pure oils, for a host of reasons.

In short, these results tell you what compounds and chemicals were found in the substance they tested.


What Do GC/MSTest Results NOT Tell YOU?

Here’s what most companies don’t want you to know: GC/MS test results do not generally show if an oil is contaminated, unless it has been contaminated with a compound the machine and technician are trying to find. Even in really pure, quality oils, a small percentage of the result may be listed as “unknown”. It is simply not possible to have every oil tested for every compound on earth. So is the “unknown” in your oil perfectly fine, or is it something else?

In the best circumstances, a neutral, third-party lab is used. The technician signs and/or stamps the result, and it is labeled with a date as well as identifying information regarding the oil batch tested. In these circumstances, some “unknown” compounds aren’t a big deal – they’re expected and OK. If you’ve done the work to find a company you trust, you can rest easy as long as the expected components are there.



In not-so-great circumstances, the technician, oil producer, or lab can act in underhanded ways. A producer might add expected compounds to a sample, and the oil they sell you. A technician might not be one of the “good guys”, and sign off on shoddy work. Labs can choose not to test for the things you don’t want, like pesticides.

Very underhanded oil producers use a “bait and switch”. They publish test results for “lavender” on their sales page. You look, and they are good results, with the expected components. What’s in your bottle? Lavender-scented oil. Or poor quality lavender. Or something that smells a lot like lavender. This is why I suggest buying only from those companies who operate with transparency, who list batch numbers on test results and bottle labels. One Amazon seller had actually used a GC/MS result published on an independent site as a photo in their product listing. I easily discovered the exact same result, published five years prior, on the independent site. Five years! And the exact same report is still on the exact same page.  I’ve given that company several bad reviews – which you should learn to read well if you buy oils online.


Um, What Now?

If you’re using a company’s published GC/MS testing to tell you whether an oil is contaminated with pesticides, you’re probably disappointed right now. We’re trained to look for test results in almost every area of life as a standard for quality. But if a company wants to be underhanded, the results tell you nothing. What do you look for?

You look for a company who not only publishes results from batch-specific testing, you look for one who uses it for their own benefit as well. Look for the company who takes pride in producing amazing oils. You look for all of the things on this list, not just whether there’s a GC/MS report somewhere on the website. Because the report doesn’t list “pesticides” or “chemical fertilizer”, you have to work with a company who produces oils properly. Because the report doesn’t tell you where the compounds originated, you have to work with a company that proves itself in other ways.

GC/MS testing tells you a whole lot about what’s in your oil, and what might not be. But it’s important to keep seeking information if you’re hoping to get the very best oils available for your needs. The links in this article, and those below, will help you get started. Or keep going, as the case may be, to find exactly what you’re looking for!

Information All Companies Should Provide – Check before you buy!

Understand Your Terms – Don’t be fooled by a label with no meaning.


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