Advances in liquid chromatography coupled to mass spectrometry for metabolic phenotyping

• Ultra-high-pressure liquid chromatography (UHPLC) in untargeted metabolic profiling.
• Reversed-phase LC + hydrophilic interaction chromatography in metabolic profiling.
• Very polar metabolites require alternative approaches, such as ion-pair LC.
• Miniaturization and supercritical fluid chromatography for metabolic phenotyping.

We review the separations currently employed in the field of global metabolic profiling and based on the use of liquid chromatography (LC) coupled to mass spectrometry. Currently, most LC separations are performed using reversed-phase (RP) methods, with hydrophilic interaction chromatography a popular choice for polar compounds that are not well served by the RP mode. The use of ultra-(high)-performance LC [U(H)PLC] is seen to be increasingly replacing conventional high-performance LC (HPLC) in metabonomic/metabolomic applications as its benefits are seen as essential for rapid, high-resolution sample analysis. We discuss alternative, and emerging, methods of sample profiling, based on the miniaturization of HPLC-type separations, or the application of supercritical high-performance and ultra-high-performance chromatographic separation.