Iron, a crucial element in our environment, plays a vital role in numerous natural processes. Understanding the presence and concentration of iron in the environment is very important, as it impacts various aspects of our planet’s health. On-site detection and speciation of iron are significant for several reasons. In this context, the present work aims to evaluate the applicability of voltammetry for on-site determination of iron and its possible speciation using a portable voltammetric analyzer. Voltammetry offers the advantage of convenience and cost-effectiveness. For iron (III) determination a modification of a glassy carbon electrode (GCE) with an antimony-bismuth film (SbBiFE) using acetate buffer (pH=4) as supporting electrolyte was used. The technique adopted was Square Wave Adsoptive Cathodic Stripping Voltammetry (SW-AdCSV) and we used 1-(2-piridylazo)-2-naphthol (PAN) as iron (III) ligand. Linearity, repeatability, detection limit and accuracy were determined using synthetic solutions, then a Standard Reference Material (SRM) 1643f - Trace Elements in Water was used for validation measurements in real matrix. The procedure was finally applied to real samples (tap, lake and sea water) and the results obtained were compared by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The results obtained demonstrated the excellent applicability of the proposed on-site voltammetric procedure for the determination of iron and its speciation in water.