Determination of iodide using flow injection with acidic potassium permanganate chemiluminescence detection

A simple and rapid flow-injection method is described for the determination of iodide, based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. The calibration graph was linear over the range 1.0-12 x 10(-6) mol/L (r(2) = 0.9955) with relative standard deviations. (n = 4) in the range 1.0-3.5%. The detection limit (3 sigma) was 1.0 x 10(-7) mol/L, with sample throughput of 120/h. The effect of interfering cations [Ca(II), Mg(H), Ni(II), Fe(II), Fe(III) and Pb(II)] and anions (Cl-, SO42-, PO43-, NO3-, NO2-, F- and SO32-) were studied. The method was applied to iodized salt samples and the results obtained in the range 0.03 +/- 0.005-0.10 +/- 0.006 mg I/g were in reasonable agreement with the amount labelled. The method was statistically compared with the results obtained by titration; no significant disagreement at 95% confidence was observed. Copyright (c) 2006 John Wiley & Sons, Ltd.