On-line preconcentration of transition metal ions using 8-quinolinol-bonded chelating silica is described. The precolumn was coupled to an ion-pairing chromatographic column and simultaneous determination was achieved using a diode-array UV detector, 0.1 M potassium cyanide (pH 8.5) being used for eluting metals from both the precolumn and the analytical column. Of the metals tested, Cu, Ni, Co and Fe(II) yielded well resolved absorption bands whereas Fe(III) and Mn(II) yielded ill-characterized absorption bands. The working concentration range for Cu and Ni was tested and shown to be linear in the range 10⁻⁸−5 · 10⁻⁶M. Highly reproducible results were obtained at these concentrations. The sensitivity was found to be limited by background signals and the reason for this background is discussed in detail.