A simple spectrophotometric flow-injection method is reported for the highly sensitive and fast determination of copper(II). The method is based on the formation of coloured Cu(II)-(4-methylpiperidinedithiocarbamate)(2) complex when the copper solutions are introduced into a tertiary reagent stream containing 4-methylpiperidinedithiocarbamate. The coloured complex is then selectively monitored at 435 nm. To increase interactions between copper(II) and colour forming reagent and preconcentrate of copper(II), a microcolumn containing strong cation exchange resins was placed between injection manifold and spectrophotometer. The system required no mixing chamber and allowed a sample throughput > 60 sample h(-1). The calibration graph was linear in the range 5-100 mu g 1(-1). The detection limit was < 0.5 mu g 1(-1) for 20 mu 1 injection volume of copper(II) ion solution. The developed method was applied to environmental, copper processing water, and ore samples. (C) 1999 Elsevier Science B.V. All rights reserved.