A method of separating components having a given negative or positive charge and contained in a sample is disclosed. The method involves, in one embodiment, loading a microchannel with a sample, placed between a trailing-edge
electrolyte having a selected concentration of a titratable species, and a leading-edge
electrolyte. With the application of a
voltage potential across the microchannel, charged components in the sample stack by
isotachophoresis, and electrolytic hydroxyl or
hydrogen ions formed by
electrolysis at the upstream-end
electrode migrate into the trailing-edge
ion buffer, titrating the titratable species therein, where the concentration of the titratable species in the trailing-edge
electrolyte is selected , in relation to the lengths of the upstream channel region and sample-loading volume, to permit the sample to stack into a relatively
small sample volume before electrolytic-
ion migration from the upstream
electrode into and through the sample-volume region is effective to overtake the charge sample components. With continued application of an
electric potential across the channel ends, charged sample components in the stacked
sample volume separated by zone
electrophoresis.