In order to verify the quality of the essential oils, a representative sample of each lot is analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). This test identifies the individual components of an oil and gives information about their percentage in the composition. The GC/MS analysis identifies the constituent components by

• Comparing the GC retention time with a retention time library and comparing the mass spectrum with a mass spectra library that contains a substantial number of entries.
• Comparing the components with pure 'standard samples' to detect any contamination.
• Cross referencing with other essential oils and comparing with the published data of essential oils.

In Nepal there are no laboratories which can perform these tests, so the samples are sent abroad.

The physical properties of the oils such as their refractive index, specific gravity, optical rotation etc, are also tested to ensure that they are within a standard range.