A new simple, and rapid flow-injection spectrophotometric method is developed for the determination of trace amounts of Cu(II) by using a new chromogenic reagent acetylsalicylhydroxamic acid (ACSHA). The method is based on the formation of colored Cu(II)-(AcSHA)2 complex. The optimum conditions for the chromogenic reaction of Cu(II) with AcSHA is studied and the colored (green) complex is selectively monitored at lambda(max) 700 nm. With the reagent carrier solvent (dimethylsulfoxide (DMSO) and acetate buffer, pH 4.2) flow-rate of 1 ml min(-1) a detection limit (2S) of 1 mug l(-1) Cu(II) was obtained at a sampling rate of 80 sample h(-1). The calibration graph was linear in the Cu(II) concentration range 5-120 mug l(-1). The relative standard deviation (n = 10) was 0.64% for a sample containing 60 mug l(-1) Cu(II). The detailed study of various interferences confirmed the high selectivity of the developed method. The method was successfully applied to determine trace amounts of copper(II) in river and seawater samples. The accuracy of the method was demonstrated by the analysis of standard reference materials C12X3500 and C14XHS 50. (C) 2003 Elsevier Science B.V.,All rights reserved.