Use of a Prior-Oxidation Procedure for the Determination of Iodine by Inductively Coupled Plasma-Atomic Emission Spectrometry

Abstract

A simple prior-oxidation procedure is described for the determination of low concentrations of iodine by inductively coupled plasma-atomic emission spectrometry (ICP-AES) in the ultraviolet and vacuum ultraviolet (VUV) regions of the spectrum. For measuring spectral lines in the VUV region, the monochromator and the enclosed external optical path between the ICP source and the entrance slit of the monochromator have both been purged with nitrogen to minimize oxygen absorption below 190 nm. Iodine atomic emission lines at 206.16 and 183.04 nm have been selected as the analytical lines. The ICP-AES intensity is enhanced by a factor of up to 50 by prior oxidation of the iodide to elemental iodine using several oxidizing additives, presumably because of increased sample-transport efficiency between the nebulizer and the plasma. The best attainable detection limits (3-σ criterion) for iodine at 183.04 and 206.16 nm were 2.00 and 13.9 ng/mL, respectively, in the presence of 3.5-M perchloric acid or 0.2-M hydrogen peroxide, while the corresponding detection limits were 0.088 and 0.56 μ/mL in the absence of an oxidizing additive. The typical analytical working graphs obtained under the optimized operating conditions were rectilinear over approximately five orders of magnitude in concentration.