How to Buy Essential Oils Smart: A Guide to Chemical Composition, GC/MS, and Botanical Nuances

In the world of essential oils, it's easy to succumb to clichés: "lavender for sleep," "mint for headaches," "tea tree for acne." However, an essential oil isn't a magical product, but a chemical substance —natural, beautiful, but chemical. And like any chemical substance, it can have therapeutic effects... or irritate, cause allergies, or interact. The devil is in the details. And the details? In GC/MS, botanical name, and chemical composition.

1. GC/MS - Certificate of Truth (or Lack of It)

GC/MS, or gas chromatography/mass spectrometry , is a chemical test that identifies all the volatile compounds present in an oil . It provides a chemical fingerprint of a given batch of oil.

Why is this so important?

Even if we are dealing with the same plant ( Lavandula angustifolia ), the chemical composition of the oil may differ dramatically depending on:

• climate,
• height of crops above sea level,
• soil type (pH, moisture),
• time and method of distillation,
• moment of harvest.

Example: Lavandula angustifolia and the presence of camphor - from sleep to stimulation

Many people associate lavender with its relaxing scent and sleep-inducing properties. And rightly so – but not all lavenders are created equal. The key ingredient that influences its action profile is camphor – a compound from the ketone group with a strong, penetrating aroma and circulatory and stimulating properties.

Here's how the camphor content changes the use of Lavandula angustifolia oil:

GC/MS is the only reliable way to verify whether the bottle contains what the label promises. Because the sense of smell? It can be unreliable.

2. Chemical composition - the heart of action

Essential oils are composed of hundreds of chemical compounds : terpenes, esters, phenols, aldehydes, alcohols, ketones… Each of them has its own role – and its own limitations.

Carvacrol - a compound from the phenol group

It is found mainly in oregano oil ( Origanum vulgare ) , known for its strong antibacterial properties.

• The carvacrol content of over 70% makes the oil act as a natural antibiotic.
• But also: it can strongly irritate the mucous membranes , is hepatotoxic in long-term use and is absolutely not suitable for use without dilution.

Oregano? Yes - but with knowledge, caution, and after GC/MS.

Estragole (methyl chavicol) - present in basil oil ( Ocimum basilicum )

• High concentrations may irritate the nervous system and be potentially carcinogenic in large doses.
• Some basil chemotypes have more of it, others less - and here we come back to the chemotype and botanical name .

3. Chemotypes - the same plant, but with different therapeutic DNA

Sometimes the same plant produces an oil with a completely different composition , depending on environmental conditions. For example?

Thymus vulgaris - thyme .

It can be available in the following versions:

• CT thymol - strongly antibacterial, but irritating (a lot of thymol - phenol).
• CT linalool - milder, anti-inflammatory, safer for use in children.
• CT geraniol, CT carvacrol, CT borneol - each of them has different properties and uses.

A chemotype is like a "therapeutic subspecies" - if you don't see it on the bottle, you don't know what you're buying.

4. Botanical names - Latin passport of the oil

Essential oils can't be identified by their trade name. "Lavender" isn't enough. We need a Latin key.

Example:

• Lavandula angustifolia - delicate, regenerating, gentle.
• Lavandula x intermedia - so-called broad-leaved lavender (e.g. Grosso), contains more camphor.
• Lavandula stoechas - strong, but may be neurotoxic - not recommended for children and pregnant women.

Without a botanical name, you can't build trust. It's like buying herbs by weight without a label.

5. Product description - between marketing and reality

Last but not least: the product description.

• Does it contain a botanical name?
• Is the country of origin specified?
• Is there an expiration date?
• Does the manufacturer provide a batch number (important for GC/MS)?
• Will you find information about the extraction method (steam distillation, pressing, CO₂)?

Lack of this data = lack of trust.

6. Abbreviations you need to know: spp., CT, EO

spp. = species pluralis - means "different species." When you see Thymus spp. , it means the exact variety is not specified. And that's cause for concern.

CT = chemotype – the key to understanding what plays the main role in an oil. The same species (e.g., thyme) can have different CTs: linalool, thymol, carvacrol – and each of them works completely differently.

EO = essential oil - an essential oil, i.e., a distillate from a plant. Not to be confused with "fragrance oil" (synthetic fragrance) or "fragrance oil."

7. Ingredients that smell like… a red flag

Here is a list of chemical compounds that are worth paying special attention to