Comprehensive Lipid Profiling by Multisegment Injection–Nonaqueous Capillary Electrophoresis–Mass Spectrometry: Expanding Coverage Beyond Hydrophilic Metabolites

Lipidomics aims to comprehensively analyze a diverse range of lipid classes in complex biological samples, including non‐esterified fatty acids and glycerophospholipids. Methods developed for quantitative lipid profiling over the past 70 years have closely mirrored technological advances in analytical instrumentation involving separation science and mass spectrometry (MS). Nonaqueous capillary electrophoresis (CE) offers a viable high‐efficiency microseparation platform for resolving water‐insoluble compounds using a conductive electrolyte in a compatible organic solvent or miscible organic solvent mixture typically containing a low fraction of water in solution. In 2013, the authors' group first introduced a multiplexed separation method for high‐throughput metabolite analyses based on multisegment injection–CE–MS, which incorporates a serial injection of seven or more samples within a single run. Metabolome coverage is expanded to encompass hundreds of ionic lipids in blood or tissue sample extracts and thus is no longer limited to polar/hydrophilic metabolites using aqueous‐based CE–MS methods.