A new liquid chromatography instrument is described that employs small-diameter capillary columns and an optically controlled sample gating procedure to separate a mixture of fluorescein isothiocyanate (FITC) labeled amines in as few as 6 s. Efficiency of the separation, expressed as the number of theoretical plates, is observed to increase linearly with column length and thus analysis time. The combination of short analysis time and automated sample introduction allows signal averaging to be used to enhance the precision of the measurement.