The ferrozine method revisited: Fe(II)/Fe(III) determination in natural waters

The original ferrozine method has been modified to sequentially determine t he Fe(II)/Fe(III) speciation in small volumes of fresh and marine water sam ples, at the submicromolar level. Spectrophotometric analyses of the Fe(II) ferrozine complex are performed on a single aliquot before and after a redu ction step with hydroxylamine. The procedure is calibrated using Fe(III) st andards stable under normal conditions of analysis. It is shown also that t he presence of high concentrations of dissolved NOM (natural organic matter ) do not create any significant artifacts. The method was used to measure F e(II) and Fe(III) depth distribution in salt marsh pore waters and in a str atified marine basin. (C) 2000 Elsevier Science Ltd. All rights reserved.