Essential oils analysis. I. Evaluation of essential oils composition usingboth GC and MS fingerprints.

The chemical nature of essential oils makes them suitable for analysis usin g a gas chromatography-mass selective detector (GC-MSD). Mass spectra (MS) libraries can not be used as unique and absolute criteria for the identific ation of chromatogram peaks. The wide variety of MS of the libraries, recor ded in different conditions, can lead us to erroneous results. In order to increase the reliability of the analytical results, we used as identity cri teria, both GC fingerprints resulted from the relative retention indices (R RI) and the recorded MS of the separated compounds. The two criteria have b een quantified by their correlation with the standards. A new parameter cal led global composition evaluation index (I-GCMS), which resulted from a wel l-balanced average of the two criteria, has been defined. Because the compa rison of the results of the MS with databases is more accurate than the RRI , we considered that the ratio of the two criteria must be at least GC:MS 1 .2. A database containing RRI of about 600 components, widely found in esse ntial oils composition and separated on HP-5 column, was created. Two macro s based on the Microsoft Excel spreadsheet were also created. The program o ffers the best 20 matches of each compound with the combined MS and RRI lib rary. The composition of Romanian Acorus calamus L. essential oil was estab lished and the results were compared with those obtained by 'classical' met hods. (C) 1998 Elsevier Science B.V. All rights reserved.