Abstract An on-line vanadium preconcentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated to flow injection (FI) was studied. For the retention of vanadium, 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and Amberlite XAD-7 were used, at pH 3.7. The vanadium was removed from the microcolumn in countercurrent with nitric acid. An enrichment factor (EF) of 75 was obtained. The detection limit value for the preconcentration of 50 ml of aqueous solution of vanadium was 0.04 μg l −1. The precision for 10 replicate determinations at the 5 μg l −1 vanadium levels was 2.5% relative standard deviation (R.S.D.), calculated with the peak heights obtained. The calibration graph using the preconcentration system for vanadium was linear with a correlation coefficient of 0.9996 at levels near the detection limits up to at least 50 μg l −1. The accuracy of the method was demonstrated by analysing a standard reference material NIST SRM 1640 trace elements in natural water. The method was successfully applied to the determination of vanadium in drinking water samples.