The effects of stationary phase and mobile phase additive on fluorescence signal intensities of dansylamino acids were examined in microcolumn liquid chromatography. Sodium dodecyl sulfate (SDS), employed as the mobile phase additive, was dynamically introduced into an anion exchanger, and it worked as a stationary phase in the reversed-phase mode. Signal enhancement was achieved by on-column fluorimetric detection owing to the focusing and environmental effects of the SDS stationary phase.