Capillary electrophoretic techniques toward the metabolome analysis*

Metabolome analysis is a systematic chemical analysis of metabolites, which may be used to investigate the metabolic activity in the cell. Capillary electrophoresis (CE) is one of the most promising techniques for the metabolome analysis, because it gives high-resolution separations in a reasonable time and requires a minimum amount of samples. General characteristics of CE are discussed from the viewpoint of metabolome analysis. Micellar electrokinetic chromatography (MEKC), a separation mode of CE, enables the separation of neutral analytes by using micelles as pseudostationary phases. MEKC is also powerful for the separation of ionic analytes to improve selectivity. To solve relatively poor concentration sensitivity with UV absorbance detection, on-line sample preconcentration techniques were developed resulting in up to few thousand-fold increases in sensitivity. Laser-induced fluorescence detection is another solution to increase concentration sensitivity, but most analytes are not natively fluorescent. Therefore, several derivatization reactions were performed to selectively detect a class of analytes with high sensitivity. Some preliminary results are shown with formic acid extracts of Bacillus subtilis.