Application of a bismuth film electrode to the voltammetric determination of trace iron using a Fe(III)-TEA-BrO3- catalytic system

A sensitive catalytic voltammetric method for determining trace iron at a bismuth film electrode (BiFE) is described. The method is based on the cathodic reduction of the Fe(III)-triethanolamine (TEA) complex to Fe(II). It has been proved that the addition of KBrO3 causes rapid oxidation of Fe(II) and TEA, and therefore results in a large increase in the analytical signal from Fe(III) when TEA is placed in alkaline solution. When TEA was present in the solution, operating the BiFE under optimized conditions yielded a stable catalytic voltammetric response for iron, with high sensitivity (0.88 mu A mu M-1), good precision (RSD=3.9%) and a low detection limit (7.7x10(-9) M), obtained without any preconcentration procedure. Possible interferences from the coexisting ions and surface-active substances were investigated. Finally, the method was applied with satisfactory results to the determination of iron in certified reference river water samples.