What is GC/MS Testing and Why is it Important? - Everyday Essentials

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PLant Therapy Essential Oil Testing Batch Test Reports

What is GC/MS Testing and Why is it Important?


Here at Plant Therapy  each and every one of our batches of oil is GC/MS tested for quality and purity. These batch-specific GC/MS reports are available right on our website for the convenience of our customers. Often times we are asked what a GC/MS test is, why it is so important, and how to read the tests. These are important questions and today we are happy to address them for you.

What is a GC/MS test?

Before we can discuss why GC/MS testing is so important we must first determine what a GC/MS test is. In a recent discussion with Alexis St-Gelais, one of the chemists we work with from Laboratoire PhytoChemia, he defined GC/MS testing when applied to essential oils as “an analytical chemistry technique allowing for separation, identification and partial quantitation of individual volatile molecules present in an essential oil. The technique thus allows to fingerprint the essential oil sample, whose profile can then be compared with reference profiles and screened for contaminants or adulterants.” [1]

A GC/MS test is completed using two separate techniques, GC or Gas Chromatography, and MS or Mass Spectrometry. To really know what GC/MS is we must discuss the separate parts and what takes place in the process. “The GC separates the chemical mixture into pulses of pure chemicals based on volatility or ease with which they evaporate into gas. Similar to a running race where a group of people begin at the starting line but as the race proceeds the runners separate based on their speed. The chemicals in the mixture separate based on their volatility. In general small molecules travel more quickly than larger molecules.” [2]

“The MS identifies and quantifies the chemicals based on structure. Let’s say after completing a puzzle you accidentally drop it on the floor. Some parts of the puzzle remain attached together and some individual pieces break off completely. By looking at these various pieces you are still able to get an idea of what the original puzzle looked like. This is very similar to the way the mass spectrometer works.” [2]

A drop of essential oil surrounded by orange peels

Why is GC-MS Testing Important?

Now that we know what a GC/MS test is and how it works let’s discuss why it is so important when it comes to essential oils. As Alexis mentioned, this test allows us to fingerprint each sample showing us the unique identity of the essential oil. These tests are very important from a quality standpoint as it shows us the oil’s chemical makeup. Most contaminants or adulterants show up with these tests, and for those that don’t, if we suspect that some of what looks like a natural constituent of an oil might be a synthetic addition, we use chiral analysis – a more sophisticated form of gas chromatography – to find out if it is in fact, a natural constituent or a synthetic addition.

GC/MS testing is also important because it shows us a breakdown of the main chemical constituents that give an essential oil some of its therapeutic properties. For example, if you would like to create a blend to help you relax before bedtime you might look for an essential oil that has a high content of Linalool. Along with having many other benefits, this constituent has been shown to be helpful for sleep and relaxation. By viewing the batch-specific GC/MS reports for oils like Ho Wood Essential Oil, Coriander Essential Oil, and Lavender Essential Oil you can determine that each of these oils has a higher content of Linalool, making them good choices for such a blend.

The safety considerations of each individual oil are also determined by the chemical profile.

For example, here at Plant Therapy, we do not include essential oils that have a high 1,8-Cineole content in our KidSafe line. We avoid high amounts of this constituent with children as it may cause breathing issues for some. Through GC-MS testing we can determine the levels of 1,8-Cineole and decide whether or not an essential oil will be a part of our KidSafe line.

Woman's hand writing in her notebook

How to Read Plant Therapy’s GC/MS Reports

The first page of Plant Therapy’s batch-specific GC/MS reports provides the results of organoleptic testing, the botanical name, and the country of origin of the essential oil.

The following page of the GC/MS report is the sample identification page. This page contains both Plant Therapy’s lot-specific batch code and the third-party tester’s internal code. You can also find information on the method of testing used, the analyst, and the date of the analysis.

The next page or pages will include a list of the identified compounds, the percentage of which they are found in the essential oil, and the molecular class. When viewing these pages you may notice that there are two different columns listed with percentages, BP5 and WAX. These are two different types of GC/MS analysis. One is no more or less correct than the other. It reminds us that these numbers are never precise. In these two columns, you may find percentages that are listed in brackets meaning that two or more constituents are represented by one number and that the analysis was unable to identify the correct percentage of each constituent. After all of the components of the oil have been identified you will then find the conclusion from the lab.

The last page or pages consist of the Mass Spectrum which is defined as “a spectrum of charged particles, arranged in order of mass or mass-to-charge ratios.” [3] This provides the same information that is listed in the identified compound list but in graph form.

Plant Therapy is one of the only essential oil companies that offer batch-specific GC/MS reports for our customers to review without having to request anything. You can find these reports under the “Test Reports” tab on the product page of the single essential oils.  If you have any additional questions on GC/MS testing or Plant Therapy’s reports, please feel free to email our Aromatherapist team at [email protected].


[1] Alexis St-Gelais, M. Sc., chimiste, Directeur scientifique, Laboratoire PhytoChemia

[2] https://courses.ecampus.oregonstate.edu/oer/gcms/

[3] http://www.dictionary.com/browse/mass-spectrum


42 thoughts on “What is GC/MS Testing and Why is it Important?”

  • Thank you PT for helping me understand the GC-MS reports. I’m fairly intelligent, but they scared me off. I fear no more!

  • Thank you so much for this information. Plant Therapy has yet to disappoint me. It seems that Everywhere I end up telling somebody about plant Therapy Oils!

  • So when looking at the identified compounds pages, what do RT and RI stand for? If I’m trying to find an oil that is high in a specific compound, which column should I be using? What do BP5 and WAX stand for? I am a Certified Aromatherapist, but I can’t seem to find the answers to these questions…..thanks

    1. Hi Pamela, RT stands for retention time and RI stands for retention index. BP5 and WAX are two different types of GC-MS analysis. One is no more or less correct than the other. It reminds us that these numbers are never precise. For our Key Constituent Chart, we pull the majority of the constituents from the BP5 column. If we find that there is a coeluting percentage we then turn to the WAX test results. I hope this helps!

  • Thank you for Your GC/MS reports. I have been purchasing your essential oils for more than 3 years. I am a Certified Aromatherapist and Certified Teacher of Aromatherapy. I want to stress the importance of having these tests available, not only for the testing, but also the date of distillation. This is so important for shelf life information,as I make my own blends. I adore the fact that you have Robert Tisserand on your team, as his book is my go to on a daily basis.

  • Thank you for posting your test results on your product pages. THIS is why I’m switching from one of the large, well known companies to Plant Therapy. They are not as transparent with their results.

  • Hi Emilee! Thank you for the great information! When I wanted to start purchasing eo’s I didn’t want to join a mlm business. I deliver mail and two of my customers recommended Plant Therapy. I tried your product and love it. Still learning, but love it. I also get excited when I deliver your product, but even more so when I get mine! 🙂 Ana

  • How many times is the batch distilled? Are the oils safe for ingestion (realizing some will need to be diluted)?

    1. Thanks for asking Kerri. The majority of Plant Therapy’s essential oils are single distillations with a few exceptions. We do carry FCF Bergamot which has had the furocoumarins removed making it safe for use in the sun. You can ingest Plant Therapy’s essential oils although we only recommend doing so while under the care of someone who is qualified to administer them in such a manner. You can read more about ingestion here: https://www.planttherapy.com/blog/2014/01/14/can-essential-oils-be-ingested/

  • I’m really interested in knowing if you support the growers and harvests of the plants, trees, seeds, flowers, etc that are used to extract the oils. Aka fair trade. Living in a tropical country that produces many plants that are used for such purpose has made me realize this people is the one that receives less dividends from such businesses.
    Therefore their families and sorroundings are never improved and this affects directly the quality of living among other things of these persons and their countries.

    1. This is a very important question Joe and I am glad that you asked. Plant Therapy works with top suppliers and farmers throughout the world and every measure is taken to ensure that everyone is treated fairly. Our goal has always been to have the greatest possible impact on the most people possible. This is why we travel to visit the farms we work with, to ensure they meet our high standards, not only on a quality level but also in regards to how workers are treated. You can read about a recent visit here: https://www.planttherapy.com/blog/2016/09/13/certified-organic-argan-oil-sourcing-expedition-to-morocco-africa/

  • I love Plant Therapy oils! They are the genuine article! They put quality first. I have experienced real results! I know this article is correct because I have felt a big difference in my health and well being!

    1. Scott, we are excited to hear that you are seeing such great improvements in your health and overall well being. Thank you for taking the time to share your feedback. Have a great day!

  • Thanks a lot with this explanation…andcyour great products. As it s sometimes better to understand with infographics, would you have an example of a GC/Ms for a high quality essential oil and one for an adulterated essential oil?

    1. We don’t have any infographics for our GCMS reports for the time being but I think this is a great suggestion and will certainly look into it! If an oil were adulterated the lab would state that in the “comments” section on the report. I hope this helps and thank you for your feedback!

  • This is such an excellent article. I’m currently studying to become a certified aromatherapist. I’ve been learning how to treat and interpret GC/MS reports. This just further solidifies my trust and love for Plant Therapy. Thank you so much for your honesty, transparency, and love for your customers. I’m continually amazed. I will always refer my clients to you all for their oil needs. Thank you again for an amazing article!

    1. Molly, I’m thrilled for you to get your certification and wish you all the best. Thank you so much for your kind feedback and for choosing Plant Therapy!

  • Thank you for this great blog. I’ll share it with others who ask why I love and recommend Plant Therapy oils.

  • Excellent information! How do we receive the GC\MS information on the oils you ship in the oil of the month club?

      1. I have done that in the past but no one ever got back to me. I emailed again hopefully this time some one will.

  • Thank you for explaining the GC/MS test. I know its important to be able to view this test for essential oils to determine their quality, but didn’t know how to read them. This really helped.

  • With all of the fraud and dishonesty today in products and services we choose to spend our hard earned penny on it is good to know that there are still some honest companies and persons that do their job to provide high quality especially when it comes to health products etc. I, for one, trust Plant Therapy to deliver and appreciate your transparency on the products you sell. Thank you!

    1. Plant Therapy is all about honesty, transparency, and offering the highest quality essential oils at a price everyone can afford. We are so happy to have you as a customer and appreciate your kind words. Have a great day and thank you for choosing Plant Therapy!

  • Is there a way of looking at your Plant Therapy bottles to see what batch they are and then asking for the GC/MS testing at a later date? I have a ton of PT oils but I had never bothered to download/get the GC/MS reports because I didn’t know how to read them. I am working on learning how to understand them and would like to start a folder of reports for the oils I have.

    1. Great question Linda! All of Plant Therapy’s bottles of essential oil have a batch code printed right on the bottle. For help with finding the location on your bottles please email an Aromatherapist at [email protected] and we would be happy to send pictures.

    1. Thanks for asking Elizabeth! If we find that a synthetic or a natural occurring constituent has been added to the essential oil we do not buy the oil. It is of the utmost importance to Plant Therapy to only offer the highest of quality essential oils that are 100% pure and natural. For more information on our quality procedures please head on over to our quality page on our website. https://www.planttherapy.com/essential-oil-quality

  • Great information! Enjoy being educated on essential oils. Use Plant Therapy essential oils and am very pleased with them. Thank you for an excelllent, pure product!

    1. I’m happy to hear that you are enjoying your Plant Therapy products Amber and that you found this post to be helpful in learning more! Have a great day.

  • Appreciate such a thorough explanation of how your oils are tested. As a person who is fairly new to the use of essential oils, I know there can be a lot of inferior products on the market. I am amazed at the health benefits of the different oils. Thank you again.

    1. Patricia, I am so glad you found this post to be helpful in learning more about GC/MS testing. Have a great day!

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