Application of Gas-Liquid Chromatography to the Analysis of Essential Oils


*Author’s Note: This paper is dedicated to the memory of the late Ray Esdale for his valuable contribution to the work of the Royal Society of Chemistry's Analytical Methods essential oils sub-committee over the last 30 years.

The 2006 European regulation REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) requires that all producers and importers of hazardous chemicals and NCS (natural complex substance) with a European total annual volume of use of >1 ton, should register, evaluate and seek authorization for their continued use.

Due to the enormity of the task, the EU Commission set up an agency, ECHA (European Chemicals Agency), based in Helsinki, Finland, to which lead registrants from the trade are required to submit dossiers of CSR (chemical safety report) data. Amongst themselves, interested stakeholders formed SIEFs (substance information exchange forums) and consortia (for materials which are related, e.g. citrus oils) and who agreed on the highest volume European registered company users, to take the role of lead registrant on their behalf.

For all non-exempt materials (e.g. exempt is castor oil, which is non-hazardous and chemically unchanged during its cold expression from castor beans, Ricinus communis L.), the highest annual volume of use were registered as follows: >1000 tons were registered in 2010; medium volume, 100-1,000 tons, in 2013; leaving the remainder of 1-100 tons use ingredients for registration by June 2018. One of the first tasks of the SIEF was to agree on the “sameness” of the material to be registered, to ensure that the group was covering all grades of the same ingredient. For many of the applicable NCS, this was a complex task due to the multi-constituent composition of the natural products.

In 2006, an NCS task force of EFFA (European Flavour and Fragrance Association) agreed that there were 34 natural ingredients that were likely to be registered by 2013 and collated their own data. Often based upon 1,000 trade sample analyses, the data was used to give a statistically based range of components, which could potentially be used to aid the SIEFs [judged to be DRF 1 (Data Reliability Factor)2 quality data].

EFEO (European Federation of Essential Oils) then listed a further potential for 130 more NCS due for the 2018 registrations. Of these, there were many where the scientific literature was judged to have sufficient peer reviewed published papers to enable a “sameness” to be agreed. However, there were 43 NCS where further compositional information was thought to be needed to improve the DRF score of data quality. The British Essential Oil Association provided authenticated pure NCS samples of these to the RSC (Royal Society of Chemistry) AMC (Analytical Methods) essential oils sub-committee, to undertake a collaborative GLC trials under standardized conditions (judged to be DRF 2 quality data).

This method has been used in the previous publications in this series. The current 43 NCS being investigated, together with unpublished results from previous work, were divided into groups for the purpose of reporting and publication of papers, the first set being the cedarwood oils. As this work is to facilitate the REACH registration of essential oils, where a positive identification could not be made, the chemical class is given to enable dossier preparation.

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