A straightforward method for stacking an extremely large volume of a sample solution containing weakly acidic organic compounds was developed. By using alcohols such as methanol, ethanol, and 1-propanol as run buffer solvents, the electroosmotic flow was suppressed, so that analyte anions could proceed to the outlet vial against the electroosmotic flow under a reverse voltage. This effect made large-volume sample stacking possible for large anions using a bare, fused-silica capillary without intermediate polarity switching. The detection limits were in the low nanomolar range with conventional UV absorbance detection. The applicability of the technique to other organic solvents was also tested.