ANALYTE VOLATILIZATION PROCEDURE FOR THE DETERMINATION OF LOW CONCENTRATIONS OF IODINE BY INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY

A simple method is described for the generation of a continuous flow o f volatile iodine by the oxidation of aqueous iodide for the determina tion of low concentrations of iodine by inductively coupled plasma (IC P) atomic emission spectrometry in the normal ultraviolet and vacuum u ltraviolet (VUV) regions of the spectrum. For measuring spectral lines in the VUV region, the monochromator and the enclosed external optica l path between the ICP source and the entrance slit of the monochromat or were both purged with nitrogen to minimize light absorption by atmo spheric oxygen. The iodine atom emission lines at 178.28, 183.04 and 2 06.16 nm were selected as the analytical lines of interest. Of the var ious oxidation reactions investigated, an oxidizing solution of 5.0 mm ol l-1 of sodium nitrite in 8.0 mol l-1 sulfuric acid was found to be the most appropriate for the generation of elemental iodine. The gaseo us iodine is separated from the solution in a simple gas-liquid separa tor and swept into the argon stream of an ICP for analysis. The best a ttainable detection limits (3sigma criterion) for iodine at 178.28, 18 3.04 and 206.16 nm were found to be 0.39, 0.55 and 2.1 ng ml-1, respec tively. Typical calibration graphs obtained under the optimized experi mental conditions are rectilinear over approximately four orders of ma gnitude of concentration. The present method has successfully been app lied to the determination of total iodine (i.e., iodide + iodate) in s everal brine samples.