The aim of this work was to develop an on-line coupling of electrochemical preconcentration to atomic absorption spectrometry method and to apply the developed system in the determination of ultra-trace amounts of As in water samples. A flow-through electrochemical analyzer EcaFlow (Istran Ltd, Bratislava, Slovakia) was used as the preconcentration unit with a two-electrode cell. The working electrode was a reticular vitreous carbon electrode coated with gold. An atomic absorption spectrometer SP9 with a graphite furnace atomizer (Pye Unicam) was used to determine the preconcentrated As species. Preconcentration parameters were optimized for the electrochemical process.