• GCMS testing is widely known as the 'gold standard' in the chemical analysis of essential oils. In a nutshell, a GCMS analysis identifies the various constituents in an essential oil and lists how much of each constituent is present as a percentage.

  • A GCMS test is crucial in verifying the authenticity and purity of an essential oil. A report can be compared with a published standard or international specification, such as those published by the ISO (International Organization for Standardization), to confirm if it passes set criteria.

  • Beyond purity testing, a basic knowledge of GCMS is valuable to anyone who enjoys using or works with essential oils. Not only does it enable the safe application of essential oils, it can also help enhance aromatic and therapeutic blending.




Anyone who uses or formulates with essential oils will have come across the term 'GCMS' or 'Gas Chromatography Mass Spectrometry'. GCMS is often said to be the gold standard in the chemical analysis of essential oils, with a GCMS report being the unique 'fingerprint' of an essential oil. While this instrumental technique may seem overly technical at first glance, a basic understanding of what GCMS involves is extremely beneficial for anyone working with essential oils.

NDA provides an up-to-date GCMS report for every essential oil in our portfolio, which is available to view via the 'GCMS & Documents' tab on each product page. This report contains a graph showing the characteristic 'peaks' of a gas chromatography analysis, along with a table outlining the percentages of each essential oil constituent. So why is this information useful?

Simply put, GCMS analysis gives us an insight to the composition of an essential oil, which in turn helps us understand key aspects and implications surrounding using that essential oil. This includes its purity, quality, safety, and therapeutic applications (more on this below).

Additionally, the presence of GCMS testing helps identify a reputable supplier of essential oils. Ideally, essential oils from a specific producer or distillery should be assessed on an ongoing basis by a third-party laboratory that specializes in GCMS analysis. Trustworthy and ethical essential oil suppliers make these independent test reports readily available and accessible for customers to view.




Essential oils can be defined as concentrated mixtures of various plant-based compounds. These molecular compounds are often referred to as its 'constituents'. The rich scents and diverse properties attributed to different essential oils arise from the thousands of different constituents that exist in nature.

A GCMS report identifies all the different constituents within a specified essential oil, and also tells us how much of each constituent is present (as a percentage). This information allows us to make inferences about the essential oil's purity, quality, safety, and potential uses.


GCMS testing can help us verify the authenticity of an essential oil and whether it has been mixed with adulterants or contaminants. Adulteration occurs when a supplier sells a doctored or diluted essential oil disguised as a 'pure' oil in order to maximize profits. Essential oils can be adulterated in a myriad of ways, such as by adding vegetable oils, natural or synthetic compounds, or mixing with cheaper essential oils.

By comparing a GCMS report with authoritative reference textbooks or specifications such as those published by the ISO (International Organization for Standardization), it is possible to conclude whether an essential oil is authentic or not. For instance, if the report lists a compound that is not on the ISO specification and is also not a naturally-occurring compound, this can alert to a possible issue of contamination or adulteration. Similarly, if the GCMS report shows that a particular constituent is present in a highly unusual amount compared to a reference range (or in relation to other constituents), this could also signal possible adulteration, prompting further analysis or action.

A GCMS analysis is usually done alongside other purity and/or quality testing. This can include an organoleptic assessment of the essential oil as well as testing of its physicochemical properties such as its refractive index. NDA also provides the results of these latter analyses, which can be viewed in each essential oil's C of A (Certificate of Analysis) (available under the 'GCMS & Documents' tab in each product page).


The quality of an essential oil is not necessarily synonymous with its purity. If two different batches of a specific essential oil are compared, both could be 100% pure and yet still vary in quality due to factors such as the weather conditions the botanical was exposed to, the timing of the harvest, the distillation technique, and how the essential oil was stored.

Interestingly, GCMS testing in itself cannot provide a definitive assessment of essential oil quality. This is because there are many elusive factors that can give rise to a 'high quality' therapeutic oil and not all of these can be quantified or put into numbers! However, what GCMS can do is help us gain an insight on certain aspects of quality by directly looking at the percentages of desired constituents. For instance, although all Lavender essential oils have certain critical constituents (such as Linanool, Linanyl Acetate, Lavendulol, and Camphor), they may be present in different proportions depending on the variety and country of origin. An individual who plans to use Lavender for its antimicrobial property, for example, may prefer one that has a good balance and a high percentage of the constituents Linalool and Linalyl Acetate. GCMS information can, therefore, be extremely helpful in helping us decide which essential oil (or essential oil variety) would work best for us based on our needs and preferences.


Essential oils are potent substances, which is why being mindful of safety while using them is critical. Key safety aspects of an essential oil, and consequent precautions, can be inferred by using its GCMS report. For instance, some essential constituents are thought to be capable of inducing seizures in certain populations. These include 1,8-Cineole and Camphor. An individual with a condition such as epilepsy should avoid essential oils containing these constituents, such as Rosemary, Sage, and Hyssop essential oils. A GCMS report, therefore, contains critical information that helps guide the safe and responsible use of essential oils, especially in vulnerable populations such as children, pets, and the elderly.

Therapeutic Applications

GCMS reports can be valuable if you are an aromatherapist or enjoy creating your own aromatic and therapeutic blends. Certain essential oil constituents are associated with specific aromas and/or therapeutic properties, which can be used to maximize the therapeutic impact of a blend.

For example, constituents such as Linalool, Linalyl Acetate, Limonene, and Citronellol have been linked to calming, relaxing, and psychologically soothing effects. It can, therefore, be helpful to choose essential oils that are high in these constituents when creating a blend to help with relaxation, difficulty sleeping, or stress-reduction. Similarly, when making an aromatic blend that emphasizes sweet, flowery, and fruity notes, essential oils that are high in esters (such as Linalyl Acetate, Benzyl Acetate, and Butyl Angelate) can be incorporated.

One caveat to keep in mind here is that as essential oils are complex, simple one-to-one relationships cannot reveal the whole story of an essential oil. After all, it is the interaction between various constituents and their resulting synergy that gives rise to the richness and diversity observed in essential oils and essential oil blends. However, GCMS analysis can enhance our understanding of the chemistry of essential oils and their overarching properties, which in turn can help us fine-tune and improve on the quality of blends and/or the therapeutic impact of a natural remedy.




Essential oils are also known as volatile oils —this means as liquids, they evaporate readily into a gaseous state. This is why their aromatic molecules reach our nose quickly and register as beautiful fragrances.

GCMS testing makes use of this property (the volatility of essential oils) in order to separate and identify the different constituents within a sample.

The technique of GC (Gas Chromatography) first separates the essential oil mixture into individual molecules. The technique of Mass Spectrometry (MS) then detects what each of these molecules are, along with their relative proportions. GC and MS are coupled together because in doing so the analytical technique becomes much more powerful and accurate at identifying the various constituents. The resulting spectrum in a report is essentially a 'fingerprint' of the chemical makeup of the essential oil.

What Happens Inside A GCMS Machine

The GC element of the analysis, where the essential oil is first introduced, consists of a stationary phase and a mobile phase. The stationary phase is simply a long, coiled tube that is coated with a highly stable liquid that does not move. Running through this tube is also an inert carrier gas, such as Helium or Nitrogen. As the gas is moving, it is known as the mobile phase. The coiled tube is placed within an oven, allowing the temperature of the set-up to be controlled as needed.

When an essential oil sample is injected, it first gets vaporized (turns into a gas). The various molecules then start moving through the tube. Some molecules, which are less volatile, are more attracted (or show affinity) towards the liquid stationary phase and take a longer time to reach the end of the column. Others, which are more volatile, are more interactive with the inert gas and move faster along the column. The combination of the mobile and stationary phases together therefore effectively separates the different constituents based on their volatility.

The GC records how long it takes for each constituent to reach its detector. Once a detection is made, a peak can be seen on the resulting gas chromatogram (graph). If two different constituents reach the detector at the same time, however, it can be difficult to distinguish between the two.

The separated compounds then enter the mass spectrometer, where they are hit by a beam of electrons. The electrons break up the essential oil compounds further into positively charged fragments. The fragments (ions) are accelerated in an electric field and deflected using a magnetic field to produce a mass spectrum. By comparing the mass spectrum with a database containing the patterns of known samples, the identity of each original molecule can be inferred.




Reading a GCMS report is relatively straightforward. The first page of an NDA GCMS report displays the gas chromatogram. Each peak of the graph corresponds to a specific essential oil constituent. The 'x' (horizontal) axis shows the retention time (RT), which, in other words, is the time taken (in minutes) for each separated compound to move to the end of the GC column. The 'y' (vertical) axis represents the magnitude of the electric signal each compound generates as it gets detected. A larger signal (and a larger peak) represents a higher concentration of a specific compound.

The subsequent pages of the GCMS report show a table that outlines the relative concentrations of each detected constituent. The table is listed according to their retention times, with the constituents having the fastest retention times at the top. The concentrations are shown as percentages. For example, the report might say that the constituent Limonene is present at a concentration of 60%. A constituent name may also be bolded if it is present in a significant amount.

The number of constituents listed depends (in part) on how sensitive the GCMS instrument is as well as the size of the laboratory's database. NDA's GCMS reports often list more than a hundred detected constituents for an essential oil.

It is important to keep in mind that this GCMS report is meant to be representative of the essential oil from a trusted supplier and is not specific to a particular batch. While the composition of every batch will show a very similar profile, there can be slight natural variations as well.




GCMS analysis forms an integral part of NDA's commitment to quality assurance. Read more on NDA's dedication to purity, quality, and fairness here.

Interested in learning more about the myths and facts surrounding essential oil purity? Check out our blog post here.

Discover our step-by-step guide for blending essential oils for aromatic and therapeutic purposes here.

Explore the reputed effects of different essential oil constituents and chemical families here.




It is important to enjoy the benefits of essential oils while using them safely and responsibly. This includes never using them undiluted, performing a skin patch test prior to use, being knowledgeable about the sun's effects after use, and sourcing them from an ethical brand known for quality and purity.

External use only

As with all other New Directions Aromatics products, essential oils are for external use only. Essential oils must never be used near the eyes, inner nose, and ears, or on any other particularly sensitive areas of skin. It is imperative to consult a medical practitioner before using these oils for therapeutic purposes.

Pregnancy and other health conditions

Pregnant and nursing women are especially advised not to use essential oils without the medical advice of a physician.

Those with the following health conditions are especially recommended to consult the advice of a physician: cancer, heart-related ailments, skin disorders or allergies, hormone-related ailments, or epilepsy.

Individuals that are taking prescription drugs, undergoing major surgery, or who are at a greater risk of experiencing strokes, heart attacks, or atherosclerosis are also advised to seek medical consultation prior to use.

Children and safety

These oils should always be stored in an area that is inaccessible to children, especially those under the age of seven.

How to conduct a skin patch test

Prior to using any essential oil, a skin test is recommended. This can be done by diluting 1 drop of the essential oil in 4 drops of a carrier oil and applying a dime-size amount of this blend to a small area of non-sensitive skin.

Essential oil side effects

Potential side effects of essential oils include redness, rash, hives, burning, bleeding disorders, decreased speed of healing, low blood pressure, dizziness, headache, nausea, diarrhea, convulsions, and rapid heartbeat. In the event of an allergic reaction, discontinue use of the products and see a doctor, pharmacist, or allergist immediately for a health assessment and appropriate remedial action. To prevent side effects, consult with a medical professional prior to use.

IMPORTANT: All New Directions Aromatics (NDA) products are for external use only unless otherwise indicated. This information is not intended to diagnose, treat, cure, or prevent any disease, and it should not be used by anyone who is pregnant or under the care of a medical practitioner. Please refer to our policies for further details, and our disclaimer below.

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