Chemical Derivatization to Enhance Capillary Electrophoresis Mass Spectrometric Analysis of Acidic Metabolites in Mammalian Cells.

The simultaneous analysis of cationic and anionic metabolites using capillary electrophoresis-mass spectrometry (CE-MS) has been considered challenging, as often two different analytical methods are required. Although CE-MS methods for cationic metabolite profiling have already shown good performance metrics, the profiling of anionic metabolites often results in relatively low sensitivity and poor repeatability caused by problems related to unstable electrospray and corona discharge when using reversed CE polarity and detection by MS in negative ionization mode. In this protocol, we describe a chemical derivatization procedure that provides a permanent positive charge to acidic metabolites, thereby allowing us to profile anionic metabolites by CE-MS using exactly the same separation conditions as employed for the analysis of basic metabolites. The utility of the overall approach is demonstrated for the analysis of energy metabolism-related metabolites in low numbers of HepG2 cells.