As a part of the study, samples of five oils together with the NC-hydrocarbon mixture were distributed to members of the essential oils sub-committee (of the analytical methods committee, RSC) with instructions to prepare a standard fingerprint chromatogram for each oil using a methyl polysiloxane non-polar capillary column. Details of the NC-hydrocarbon mixture and its application are given in Part XVII. Each member was asked to submit the chromatograms of the oils and one of the NC-hydrocarbon mixtures was run at the beginning and end of the series. The latter was to ensure that the characteristics of the column did not change during the exercise. A total of 30 chromatograms together with the retention times and percentage relative peak areas (area %), values from the flame ionization detector (FID) for each detected peak, were received. The identities of the components of interest, usually those accounting for more than 1% of the total peak area, were confirmed by two different laboratories using capillary gas chromatography/mass spectrometry (GC/MS) with identities determined by comparison with in-house and commercial mass spectral libraries.