How to Determine the Quality of Essential Oils, Part 2: What Do the Certifications Mean?

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Click here to read Part 1for more background on how to determine the quality of essential oils. AndPart 3will help you hone your senses.

While searching for essential oils on the internet you may come across some companies claiming to be approved by the ISO or to meet and/or exceed guidelines established by AFNOR or to be GRAS-approved and even one company claiming to have Certified Pure therapeutic grade/FDA approved. What exactly do the terms and certifications mean?

‘Certified Pure Therapeutic Grade’

This is a relatively new trademark by a company within the industry. They own the right to this mark, although they do not have the exclusive right to the actual words “Certified Pure Therapeutic Grade.” This is a commercial trademark that the company has registered and paid a fee for to use.

ISO: International Organization for Standardization

The International Organization for Standardization (ISO) is a worldwide federation of national standards bodies from over 100 countries, one from each country. ISO is a non-governmental organization established in 1947. The mission of ISO is to promote the development of standardization and related activities in the world with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological and economic activity.

ISO’s work results in international agreements, which are published as International Standards.  In addition to quality and environmental management systems, ISO also publishes standards that set criteria for film speed, data stored on ATM and credit cards, wine glasses for use in competitions, crayons, and more.

The ISO also provides definitions such as the one below for “essential oil.” The International Organization for Standardization (ISO) in their Vocabulary of Natural Materials (ISO/D1S9235.2) defines an essential oil as follows: “An essential oil is a product made by distillation with either water or steam or by mechanical processing of citrus rinds or by dry distillation of natural materials. Following the distillation, the essential oil is physically separated from the water phase.”

According to Burfield and Kirkham (2006-07), The ISO is the main certifying body recognized for its universally accepted standards for individual essential oils. Harris (2006) points out that ISO and AFNOR (discussed below) do not set standards for differentiating the quality of essential oils; rather, they provide specifications for “industries to use as a guide to essential oil compositions so that new batches could be utilized with minimum alteration in flavor or fragrance to the finished products.”

Cedarwood Oils: An Example of Applied ISO Standards

Harris states further that “whilst it is sometimes advantageous to know whether an essential oil falls within a ‘normal’ range, it has no inference to therapeutic properties. An essential oil can be very therapeutic and yet not fall within any accepted standard.”  An example of ISO standards is provided for Texas and Virginia Cedarwood oils.

International (ISO) standards exist for both the Texas and Virginia cedarwood oils. For the former, the alcohol content, expressed as cedrol and in the range of 35-48 percent, is specified with a minimum cedrol content of 20 percent. For the Virginia cedarwood oil, a maximum cedrol content of 14 percent is stipulated. In the United States, recent FMA standards have replaced older EOA standards and are available for Chinese, Texas and Virginia cedarwood oils. These standards specify that for the Texas and Virginia oils, the alcohols content (cedrol and related isomers) must range between 25-42 percent for the Texas oil and between 18-38 percent for the Virginia oil. The Chinese oil must have a minimum alcohol content of 8 percent (Coppen, 1995).

Note:  FMA stands for the Fragrance Materials Association. The members of the Fragrance Materials Association of the United States (FMA) include companies that invent and then manufacture mixtures of fragrance ingredients for use in a wide variety of products, including fine fragrances, shampoos, soaps and detergents. The members of FMA also include the suppliers of those ingredients. Click here to learn more about the FMA.

Association Française de Normalisation (AFNOR)

Association Française de Normalisation (AFNOR) is the French national organization for standardization and is that country’s ISO member body. There are a few companies out there who claim that their essential oils are AFNOR-approved as therapeutic-grade or even that their essential oils meet or exceed AFNOR standards.

Boy, that sounds so good. But, as stated above, AFNOR does not set standards for differentiating the quality of essential oils; rather, they provide specifications for “industries to use as a guide to essential oil compositions so that new batches could be utilized with minimum alteration in flavor or fragrance to the finished products.”

‘Generally Recognized As Safe’ (GRAS)

“GRAS” is an acronym for the phrase Generally Recognized As Safe. Under sections 201(s) and 409 of the Federal Food, Drug, and Cosmetic Act (the Act), any substance that is intentionally added to food is a food additive that is subject to pre-market review and approval by FDA, unless the substance is generally recognized, among qualified experts, as having been adequately shown to be safe under the conditions of its intended use, or unless the use of the substance is otherwise excluded from the definition of a food additive.

For example, substances whose use meets the definition of a pesticide, a dietary ingredient of a dietary supplement, a color additive, a new animal drug, or a substance approved for such use prior to September 6, 1958, are excluded from the definition of food additive.

Sections 201(s) and 409 were enacted in 1958 as part of the Food Additives Amendment to the Act. While it is impracticable to list all ingredients whose use is generally recognized as safe, FDA published a partial list of food ingredients whose use is generally recognized as safe to aid the industry’s understanding of what did not require approval.

But Does GRAS Approval Mean a Product is Safe?

According to Harris (2006), “a small number of essential oil suppliers are now labeling their products as having GRAS status and implying not-too-subtly that this means that they are of therapeutic quality and also safe for internal use. 

“Whilst there are many essential oils that do possess GRAS status, such as mint and neroli, this designation can in no way be indicative of therapeutic efficacy or risk-free intake via the oral route.

“Essential oils are used as flavor ingredients in a wide range of products and their inclusion in the GRAS category is dependent, in part, upon their defined safe maximum concentration limits in edible goods. These concentrations are generally low, as they allow for the repeated ingestion of foodstuffs on a daily basis, and thus guard against cumulative dosing and potential toxicity.”

Harris ends this particular section with “individual chemicals can be recognized as GRAS, as can adulterated/synthetic essential oils.” Essential oils which have GRAS status, therefore, do not need to be pure, do not need to be organically grown, nor do they even have to come from a plant.

Alonjavascript:void(0);g with the above items, some companies also appeal to our desire for high-quality essential oils by offering a GC/MS spec sheet on all their essential oils. Let us have a look at what a GC/MS spec is and what it may or may not tell us about the quality of an essential oil.

What is a GC/MS Spec Report?

Photo by Pixabay/devanath

A gas chromatograph is a chemical analysis instrument used to separate and identify individual constituents found within a given essential oil. Each chemical constituent of an essential oil will pass through the gas chromatograph instrument and different times and speeds. As each chemical is registered, it will produce some type of peak, from very short to very tall. (See sample below)

A gas chromatography report reveals the peaks of different chemical constituents within an essential oil, it does not, however, name the specific chemical constituent (e.g. linalol) — for this a mass spectrometry must be used.

Using a Mass Spectrometer to Detect Compounds in Essential Oils

Mass spectrometry is a technique that allows for the detection of compounds (chemical constituents) by separating ions by their unique mass. Mass spectrometry is utilized to identify specific compounds registered on the gas chromatography report.

A typical mass spectrometer has three basic parts: an ion source, a mass analyzer, and a detector. Different molecules have different masses, and this fact is used to determine what molecules are present in a sample. An individual trained in reading GC/MS data will then clearly identify the exact constituents and their quantity (e.g. 5% linalol, 25% camphor, and so on) present within a given essential oil sample. Interpretation of the information gained depends on the skill, experience and knowledge of the individual who does the analysis.

A GC-MS report may fail to reveal the age and quality of an essential oil, particularly in relation to the quality an aromatherapist is looking for. So, in general, although a GC-MS report on a given essential oil is incredibly helpful, it should not be used as the sole definitive guide to purchasing a high-quality, pure, unadulterated essential oil.

Instead, it should be used along with an olfactory appraisal, confidence in the supplier and their intentions as a supplier (e.g. are they selling inexpensive essential oils to a general market or are they selling high-quality, typically high priced essential oils specifically to practitioners of genuine aromatherapy), and other analytical techniques such as Thin Layer Chromatography, infra-red analysis, specific gravity, Refractive index and optical rotation.

How to Judge the Quality of Essential Oils

Although a GC/MS spec sheet cannot reveal the specific quality of an essential oil, it does offer valuable information on the essential oil, specifically its chemical profile and authenticity. 

According to Harris (2006), in terms of therapeutic efficacy as related to pharmacological activity, the knowledge of the composition (full chemical analysis) is of paramount importance.  A GC/MS spec report that is batch-specific for the essential oil you are purchasing will support your understanding of the therapeutic applications of the essential oil and potential safety concerns.

Most aromatherapy practitioners have been trained to understand that chemical variations occur as a result of harvest time, country of origin, soil and climate conditions, part of plant used, distillation, transport and storage parameters.

Bensouilah and Buck (2006) point out that as long as the essential oil chemistry remains within defined boundaries and occur due to environmental or genetic influences and not from adulteration, this is an accepted part of aromatherapy.


Bensouilah, J. and Buck, P. (2006). Aromadermatology. Abingdon, U.K.: Radcliffe Publishing Company.

Burfield, T. and Kirkham, K. (2006-2007). “The ‘Therapeutic Grade’ Essential Oils Disinformation Campaign.”

Burfield, T. (2005). A Note on Gas Chromotography-Mass spectrometry (GC-MS). Retrieved on Octboer 2, 2005 from National Association for Holistic Aromatherapy 

Harris, B. (2001). Editorial. International Journal of Aromatherapy, 11 (4), p.181-182.

Harris, B. (2006). Editorial. International Journal of Aromatherapy, 16 (2), p.55.

Schnaubelt, K. (2004). Aromatherapy Lifestyle. San Rafael, CA: Terra Linda Scent and Image.

Part 3: Honing Your Senses

Jade Shutes is the Director of Education for The East-West School for Herbal and Aromatic StudiesShe began her study of aromatherapy and herbs while living and working in England over 26 years ago and has been instrumental in setting educational standards and serving as President of the National Association for Holistic Aromatherapy. You can also find Jade online at Aromatic Studies.

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