How to Read a GC/MS Report

Gas Chromatography-Mass Spectrometry (GC/MS) is the gold standard for verifying the chemical composition of an essential oil. It tells you exactly what compounds are present and in what percentages. Without it, you have no way of knowing whether what is in the bottle matches what is on the label.

What the test actually does

The sample is vaporised and passed through a gas chromatograph, which separates the individual chemical compounds by their molecular weight and boiling point. Each compound then passes through a mass spectrometer, which identifies it by its unique molecular fingerprint. The result is a list of every detectable compound in the oil, with its percentage by weight.

What to look for in a report

A legitimate GC/MS report will include the batch number, the date of analysis, the name of the testing laboratory, and the analyst's signature or accreditation number. If any of these are missing, treat the report with scepticism.

For each oil, there are key marker compounds that indicate authenticity. For Eucalyptus radiata, the primary marker is 1,8-cineole, which should sit between 60% and 75% in a genuine sample. If a report shows 1,8-cineole at 90%+, the oil has likely been adulterated with synthetic cineole to boost the percentage artificially.

Common adulteration patterns

The most common forms of adulteration are: adding synthetic versions of the primary compound to inflate the percentage; diluting with a cheaper carrier oil (which shows up as a low percentage of fatty acid esters); and blending with a cheaper species of the same genus (for example, Eucalyptus globulus sold as Eucalyptus radiata).

A GC/MS report catches all of these. A certificate of analysis (COA) that only lists the primary compound without the full breakdown does not.

Our reports

Every batch of Reni Oils is tested by an independent third-party laboratory. The full report is available to download on each product page. We do not publish summary certificates. You get the complete data.