Determination of total iron in fresh waters using flow injection with potassium permanganate chemiluminescence detection

Abstract

A flow injection method is described for the determination of iron in fresh water based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. Total iron concentrations are determined after reducing Fe(III) to Fe(II) using hydroxylamine hydrochloride. The detection limit (three standard deviations of blank) is 1.0 nM, with a sample throughput of 120 h−1. The calibration graph was linear over the range (2–10) × 10−7 M (r 2 = 0.9985) with relative standard deviations (n = 5) in the range 1.0–2.3%. The effect of interfering cations (Ca(II), Mg(II), Zn(II), Ni(II), Co(II), Fe(III), Mn(II), Pb(II), and Cu(II)) and common anions (Cl−, SO 4 2− , PO 4 3− , NO 3 − , NO 2 − , I−, F−, and SO 3 2− ) was studied at their maximum admissible concentrations in fresh water. The method was applied to fresh-water samples from the Quetta Valley, and the results obtained (0.04 ± 0.001–0.11 ± 0.01 mg/L Fe(II)) were in reasonable agreement with those obtained using the spectrophotometric reference method (0.05 ± 0.01–0.12 ± 0.02 mg/L Fe(II)).