Considerable literature data are available on the composition of essential oils. However, much of this relates to small scale experimental trials. For regulation purposes, such as REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) and now U.K. REACH, detailed information on the composition of commercially traded essential oils is required.
GLC (gas liquid chromatography) fingerprint chromatograms of five authentic essential oils were obtained in a collaborative study using the recommended procedure given in in Part XVII1 of this series and are presented here (this paper represents Part XXV, cedarwood oils was Part XXIII,2 ester containing oils was Part XXIV).3 The samples examined were oils of two different commercial chemotypes of cedarleaf, two different commercial chemotypes of bitter fennel and wormwood. These were selected in consultation with the U.K. essential oil trade through the BEOA (British Essential Oil Association). The results obtained show a fingerprint gas chromatogram and a corresponding table of the composition for each oil and will enable the correct regulatory assessments to be made. The expert working group gratefully acknowledges the staff time and samples of essential oils provided by the companies involved in this study.
Experimental
These NCS (natural complex substances) were subjected to GLC analysis in one long auto-sampler run over a weekend, starting and finishing with an NC polarity calibration mix (aliphatic hydrocarbon based) as described in the RSC (Royal Society of Chemistry) fingerprinting paper, The Analyst. The assumption being made that if the calibration was correct at the start and finish of the run, all of the samples in between were correctly run.
Basic chromatographic conditions used by the group were a 25 meter to 60 meter length column of about 0.25 mm diameter and 0.25 micron film thickness coated with a non-polar stationary phase. Temperature program used was 50oC to 240oC at 4oC/minute and no initial hold time. Any inert carrier gas phase can be used and flame ionization detection. Supporting data can be provided by the use of a polarity calibrated wax phase column and mass spectrometry. This is the detailed level of GLC conditions that is also listed in the NIST (National Institute of Science and Technology) webbook of retention indices.4
This method has since been used by the ISO TC (International Standards Organisation Technical Committee) 54 committee and was used by this group in a series of RSC publications.
This paper reports the evaluation of some ketone-rich oils containing thujone and fenchone; namely two chemotypes of cedarleaf oils, two chemotypes of bitter fennel oils and wormwood oil. There are many other commercially available essential oils which are also rich in these ketones; namely armoise or white wormwood (Artemisia herba-alba Asso.), lanyana or African wormwood (Artemisia afra L. Jacq. ex Willd.), armoise or common mugwort (Artemisia vulgaris L.), horse mint (Mentha longifolia L. Huds.), boldo leaf (Peumus boldus Molina), Dalmatian sage (Salvia officinalis L.) and tansy (Tanacetum vulgare L.).
References
1. Analytical Methods Committee, (1997) Application of Gas-Liquid Chromatography to the Analysis of Essential Oils Part XVII. Fingerprinting of Essential Oils by Temperature programmed Gas Liquid Chromatography Using Capillary columns with Non-polar Stationary Phases. The Analyst, 122 (10) 1167-74
2. Analytical Methods Committee, (2019) Application of Gas-Liquid Chromatography to the Analysis of Essential Oils Part XXIII. Fingerprint GLC of selected Texas, Virginia, China, Atlas and Himalaya cedarwood oils intended for REACH registration Perfumer & Flavorist, 44 November 31-42
3. Analytical Methods Committee, (2021) Application of Gas-Liquid Chromatography to the Analysis of Essential Oils Part XXIV. Part 1 of 3: Fingerprint GLC of esters-containing essential oils: Chamomile English Perfumer & Flavorist, 46 August 42-47, Part 2 of 3: Fingerprint GLC of esters-containing essential oils: bergamot oil, clary sage oil and spike lavender oil Perfumer & Flavorist+, 46 September 36-46. Part 3 of 3 Fingerprint GLC of esters-containing essential oils: neroli oil, petitgrain bigarade oil and petitgrain oil Paraguay Perfumer & Flavorist+, 46 October 26-32
4. NIST Office of Data and Informatics (2017) SRD 69 Retrieved from https://webbock.nist.gov/chemistry
For the full article, please check out the Perfumer & Flavorist+ December 2022 issue.
