When we wish to seriously consider an Essential Oil for inclusion in our range, we send the sample to an independent laboratory to receive a full Gas Chromatography / Mass Spectrometry (GC/MS) analysis which gives us a clear idea of the purity of our Essential Oils. Every GC/MS report includes a summary of the sample’s characteristics (Refractive Index, optical rotation etc.) compared to the most up-to-date accepted standard for that oil (this can range from National Pharmacopoeia listings to recent ISO Standards, for example, our Orange analysis is based on ISO 3140: 2011 (Oil of sweet orange)).
Gas Chromatography measures the rate of elution (the separation of material by washing) of each of the components of an Essential Oil to give a clear idea of the concentration of individual compounds (high limonene concentration for citrus fruit or peel oils, high linalool content for Lavender, etc). This gives us a good idea of how closely any given oil conforms to our expectations and also gives us the opportunity to determine possible sources of contamination, so we always have an external perspective on all potential suppliers.
We request that suppliers provide us with their own Certificates of Analysis which we can check against our house standards and our own testing procedures. In our in-house laboratory we test each oil for its Specific Gravity – its density relative to water. This is likely to fall within a narrow range for each type of oil (Orange Oil comes between 0.886 and 0.896 when measured at 20˚C) and deviation from this range would indicate possible adulteration or contamination. Any oil that falls outside these parameters is rejected.
Similarly, we test for Refractive Index, or the angle of refraction of light through a substance. This depends on the composition of the oil and even small discrepancies can produce major results within the refractive index (Orange oil R.I. falls between 1.456 and 1.461when measured at 20 ˚C). In this way, we are able to track the quality of our ingredients, from the first test sample to the latest batch delivered.