Determination of total iron in fresh water's using flow injection with potassium permanganate chemiluminescence detection

A flow injection method is described for the determination of iron in freshwater 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 hydroxylarnine 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) x 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(III) and common anions (Cl-, SO42-, PO43-, NO3-, NO2-, I-, F-, and SO32-) 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)).