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The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) is modified to extract and preconcentrate metal species rapidly, avoiding the formation of hydrophobic complexes, using a mixed micellar medium. Coupling the procedure with chemiluminescence (CL) detection based on the catalytic activity of metal species on the luminol-hydrogen peroxide reaction and enhancing the signal with the presence of a micellar carrier containing bromide ions produces a powerful tool for the preconcentration and determination of metal species at ng l(-1) levels. As an analytical demonstration ultratrace concentrations of chromium were conveniently detected and quantified in samples with a complex matrix such as seawater and wastewater. The figures of merit for the determination of chromium were: 0.9-1.6% R.S.D. (n = 5) with detection and quantification limits 0.5 and 2.0 ng l(-1), respectively. The calibration graph was rectilinear from 2 to 200 ng l(-1) (r = 0.9996, n = 6). Several other metal ions were determined in ideal situations, with analogous results. (C) 2002 Elsevier Science B.V. All rights reserved. Analytica Chimica Acta