Picomolar analysis of proteins using electrophoretically mediated microanalysis and capillary electrophoresis with laser-induced fluorescence detection.

We report a method for the analysis of picomolar concentration proteins using electrophoretically mediated microanalysis (EMMA) to label proteins on-column with a fluorogenic reagent. Labeling is followed by capillary zone electrophoresis separation and postcolumn detection based on laser-induced fluorescence. The method provides a concentration detection limit (3 sigma) of 3 x 10(-13) M for conalbumin. The method provides separation efficiency of 300,000 theoretical plates. Protein extract from a human colon adenocarcinoma cell line generated a dozen major components and many minor components in a 12-min separation; the protein extract from 2.5 cells was used for this analysis. When compared to UV absorbance detection, the EMMA method provides 7,000,000-fold improvement in detection limit.