COMPARISON OF LIQUID-CHROMATOGRAPHY ELECTROSPRAY, ATMOSPHERIC-PRESSURE CHEMICAL-IONIZATION, THERMOSPRAY AND CONTINUOUS-FLOW FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY FOR THE DETERMINATION OF SECONDARY METABOLITES IN CRUDE PLANT-EXTRACTS

Different interfaces for liquid chromatography/mass spectrometry (LC/M S) such as thermospray (TSP), continuous-flow fast atom bombardment (C F-FAB), electrospray (ES) and atmospheric pressure chemical ionization (APCI) were evaluated for their potential in plant metabolite detecti on and identification. Natural products of various classes, mainly ter pene and polyphenol aglycones and glycosides from 100-3000 u, were ana lysed by LC/MS and LC/MS/MS in crude plant extracts. These studies sho wed that TSP is suitable for the investigation of moderately polar com pounds ranging up to 800 u and for glycosides having not more than two sugar units. CF-FAB permits the ionization of more polar compounds su ch as saponins bearing 1-8 sugar units. ES and APCI allowed the ioniza tion of the broadest range of metabolites but showed an important sele ctivity for polyphenol aglycones and were sensitive to the use of modi fiers (trifluoroacetic acid, ammonium acetate). The complementarity of TSP, CF-FAB, ES and APCI for crude plant extract LC/MS analysis is di scussed.