In addition to inorganic species originating from minerals and process modifiers, residues of organic process chemicals may be present in the liquid-phase of flotation tailings. From the process control and environmental points of view, it is important to be aware of the concentrations of chemicals and certain ions remaining in the tailings waters. In this study, the composition of the liquid-phase of flotation tailings at Pyhasalmi concentrating plant was analysed on-line with a commercially available process titrator. The potentiometric titration procedures were implemented in the analyser for quantitative analyses of the organic collector chemical, xanthate, and for the sum of the concentrations of calcium and magnesium along with the concentration of sulphate. The variation of the concentrations of these species from tailings waters from pyrite and copper circuits was monitored for a month. (C) 2003 Elsevier Ltd. All rights reserved.