A flow injection (Fl) on-line preconcentration procedure by using a manometer-sized alumina packed micro-column coupled to inductively coupled plasma mass spectrometry (ICP-MS) was described for simultaneous determination of trace metals (V, Cr, Mn, Co, Ni, Cu, Zn, Cd and Pb) in the environmental samples. The effects of pH value, sample flow rate, preconcentration time, and interfering ions on the preconcentration of analytes have been investigated. Under the optimized operating conditions, the adsorption capacity of the manometer-sized alumina for V, Cr, Mn, Co, Ni, Cu, Zn, Cd and Pb were found to be 11.7, 13.6, 15.7, 9.5, 12.2, 13.3, 17.1, 17.7 and 17.5 mg g(-1), respectively. With 60s preconcentration time and 60s elution time, an enrichment factor of 5 and the sampling frequency of 15 h(-1) were obtained. The proposed method has been applied to the determination of trace metals in environmental certified reference materials and natural water samples with satisfactory results. (c) 2005 Elsevier B.V. All rights reserved.