Application of flow injection spectrophotometry to the determination of dissolved iron in sea-water

Abstract

Two flow-injection spectrophotometric procedures have been developed for the determination of trace amounts of iron in sea-water. The first procedure is based on the iron-catalysed oxidation of p-phenetidine by periodate after in-valve separation/preconcentration of iron(III). The limit of detection is 0.05 µg l^–1 of iron when concentrating 6 ml of sea-water. The second procedure is based on the selective catalytic effect of iron(III) on the oxidation of N,N′-dialkyl-p-phenylenediamines by hydrogen peroxide. The limit of detection of this method is 0.03 µg l^–1 of iron with a sampling rate of 60 h^–1. The utility of both flow-injection methods was demonstrated by the determination of dissolved iron in sea-water samples, with an average recovery of 98–110% and an average relative standard deviation of 1.8–8.1%.