ABSTRACT
The study of natural products in plant extracts is an interesting challenge to LC–MS. Generally, the relevant compounds must be detected as minor components in complex mixtures. A combination of LC separation, especially to resolve isomeric structures, and MS detection is needed. Furthermore, structural information is needed for the identification and dereplication of the unknown plant constituents. Because of the complexity of the sample pretreatment procedures involved in the isolation, MS in most cases is the only applicable spectrometric technique; too much of a purified component would be needed for IR and NMR analysis. On-line analysis in relatively crude samples is obligatory for the detection of minor constituents. When electrospray ionization (ESI) or atmospheric-pressure chemical ionization (APCI) are applied for analyte ionization, structural information must be obtained by application of collision-induced dissociation (CID), either via in-source CID or preferably via MS–MS or MSn. LC–MS and LC–MS–MS have proved to be extremely successful in this area.
