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 (3σ) of 3 × 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.