Abstract:
In the light of the controversy surrounding the classification of some Acacia species, an analytical method was investigated for the chemotaxonomic classification of these species by means of their unique flower fragrances. The dynamic solvent effect (DSE ) was used as a concentrating and inlet technique for gas chromatography. The DSE is a new, high-precision technique developed at the Institute for Chromatography. Concentration occurs by accumulation of volatile compounds on a porous bed of sintered glass in an evaporating solvent film. To determine the applicability of the technique, tests were initially performed on three Acacia species of uncontroversial classification. Encouraging results led to a further 18 Acacia species being studied from a specific geographical area in South Africa. The gas chromatographic data was statistically treated by a standard computer programme that performed canonical discriminant analysis. Two dimensional scatter plots were obtained which clearly mark the position of the species in relation to one another. In this way, each investigated species could be uniquely correlated to a flower fragrance profile. The results constitute the first successful application of headspace gas chromatography in chemotaxonomy. The success is directly ascribed to the excellent inlet technique that allows highly reproducible analysis of compounds in the 1 - 100 parts per billion (109 ) concentration range.
