Application of liquid chromatography-mass spectrometry analysis in metabolomics: reversed-phase monolithic capillary chromatography and hydrophilic chromatography coupled to electrospray ionization-mass spectrometry.

Analysis of the entire metabolome as the sum of all detectable components in the sample rather than analysis of each individual metabolite is performed by the metabolomics approaches. To monitor in parallel hundreds or even thousands of metabolites, high-throughput techniques are required that enable screening for relative changes rather than absolute concentrations of compounds. Most analytical techniques for profiling small molecules consist of gas chromatography (GC) or high-performance liquid chromatography (HPLC) coupled to mass spectrometry. HPLC separations are better suited for the analysis of labile and high molecular weight compounds, and for the analysis of nonvolatile polar compounds in their natural form. Although GC- and HPLC-based profiling techniques are not truly quantitative, the compounds detecting and employing the acceptable standards may compare their relative amounts. We have demonstrated that reversed-phase monolithic capillary chromatography and hydrophilic chromatography can be successfully applied for sufficient plant crude extracts separations and metabolomics studies.