Di-2-pyridyl ketone thiosemicarbazone (DPKT) was examined as a precolumn chelating reagent for high performance liquid chromatographic separation of Co(II), Cu(II), Ni(II), and Fe(II) ions as metal chelates on a 10 mu m Bondapak C(18) (300 mm x 3.9 mm) RP column. A gradient program with a mobile phase of acetonitrile and 0.01M pH:6.0 acetate buffer is used. Acetonitrile composition is increased from 25 to 40% at 18 min and held at 40% for 18 min. A UV detector was used at 400 nm. The flow rate was 1.5 mL.min(-1). Limit of detection was determined on a 3 sigma blank basis. Interference effects from other metal ions were also investigated. The method was applied for the determination of Co(II), Cu(II), Ni(II), and Fe(II) ions in drinking and tap water samples.