Essential oils analysis. II. Mass spectra identification of terpene and phenylpropane derivatives

Mass spectra are widely used in order to identify the peaks resulting from a chromatographic separation. The most common approach to solve the problem for unknowns on whom very little other structural information is available is the use of a retrieval algorithm and a reference mass spectra database. The wide variety of mass spectra recorded with different instruments under various experimental conditions can lead to erroneous results. In order to improve the accuracy of the results, we proposed earlier an identification algorithm, which combines the information obtained from both GC and MS fin gerprints. This paper. presents a new algorithm based on the comparison of the unknown mass spectra with several libraries (including Wiley and NIST) by using reverse and direct search algorithms respectively. The results of the comparisons were quantified with respect to the match quality and the i nterference compounds. A global match index for the comparison using all th e above information was computed and the results were presented as the matc h probability. This index expresses more accurately the matches between unk nown and all the available libraries mass spectra. In order to verify our a lgorithm, we tried to identify the compounds separated by GC-MSD from diffe rent species of. Acorus calamus L. (Araceae) essential oils. The probabilit y of the matches increases compel-ed with the quality of matches resulting from Wiley and NIST libraries. (C) 2001 Elsevier Science B.V. All rights re served.