Analyte volatilization procedure for the determination of low concentrations of chlorine by atmospheric-pressure helium microwave-induced plasma atomic emission spectrometry

Abstract

A simple method is described for the generation of a continuous flow of volatile chlorine by the oxidation of aqueous chloride for the determination of low concentrations of chlorine by atmospheric-pressure helium microwave-induced plasma atomic emission spectrometry (He MIP-AES). The chlorine atom emission line at 438.976 nm and ion emission lines at 479.454 and 481.006 nm were selected as the analytical lines of interest. Of the various oxidation reactions investigated, two analyte volatilization reactions with potassium permanganate and perbromate in combination with sulfuric acid were found to be the most appropriate for the generation of elemental chlorine. The gaseous chlorine is separated from the solution in a simple gas–liquid separator, dried with concentrated sulfuric acid and swept into the MIP with helium carrier gas for analysis. The best attainable detection limits (3σ criterion) for chlorine at 438.976, 479.454 and 481.006 nm with the use of potassium permanganate as an oxidant were found to be 29.9, 6.8 and 12.3 ng ml−1, respectively. Typical calibration graphs obtained under the optimized experimental conditions are rectilinear over approximately three orders of magnitude of concentration. The present method has successfully been applied to the determination of chlorine as chloride in several water samples.