Sheathless Capillary Electrophoresis-Mass Spectrometry for the Profiling of Charged Metabolites in Biological Samples.

Capillary electrophoresis (CE) is well suited for the profiling of highly polar and charged metabolites as compounds are separated on the basis of their charge-to-size ratio. The protocol presented here is based on using a recently developed sheathless interfacing design, i.e., a porous tip interface, for coupling CE to electrospray ionization mass spectrometry (MS). It is demonstrated that sheathless CE-MS employing a bare fused-silica capillary at low-pH separation conditions can be used for the profiling of both cationic and anionic metabolites by only switching the MS detection and electrophoretic separation voltage polarity. The proposed sheathless CE-MS protocol allows efficient and sensitive profiles to be obtained for a broad array of charged metabolites, including amino acids, organic acids, nucleotides, and sugar phosphates, in various biological samples, such as urine and extracts of the glioblastoma cell line.