Fig. 2

Representation of the reduction of sample content complexity during different solid phase extraction (SPE) procedures necessary for plant hormone analysis. The horizontal position represents different physicochemical properties of a metabolite (e.g., polarity, acidobasic properties, stability, volatility), whereas the vertical position and circle size represent the metabolite’s abundance in vivo. Crude extracts of plant material are complex and contain a large number of different chemical species—metabolites. The complexity of these extracts can be reduced using solid phase extraction (SPE), which retains or excludes certain metabolites with given physiochemical properties. SPE procedures can be simple or complex and time-consuming, resulting in a lower or higher degree of sample purification, respectively. LC–MS analysis of samples containing a wide spectrum of metabolites is hindered due to the presence of many abundant matrix components (represented by a yellow chromatogram). Complex and time-consuming SPE allows only a narrow spectrum of analytes to be preserved, but LC–MS analysis can than detect low abundant metabolites/plant hormones. Plant hormonomics aims for detection of a wide spectrum of metabolites. However, this may preclude complex SPE procedures, which are often essential for the successful analysis of plant hormones