Analyte volatilization procedure for continuous-flow determination of bromine by atmospheric pressure helium microwave-induced plasma atomic emission spectrometry

Abstract

A simple method to generate a continuous flow of volatile bromine by oxidation of aqueous bromide is described for the determination of low concentrations of bromine by atmospheric pressure helium microwave-induced plasma atomic emission spectrometry. The bromine atom emission lines at 447.78 and 734.86 nm and the bromine ion emission line at 470.49 nm were selected as the analytical lines of interest. Of various oxidation reactions investigated, an oxidizing solution of 100 mmol dm–3 of potassium persulfate in 5.0 mol dm–3 sulfuric acid is the most appropriate for the generation of elemental bromine. The gaseous bromine is separated from the solution in a simple gas–liquid separator, dried with a desiccant of anhydrous calcium chloride and swept into the helium stream of a microwave-induced plasma for analysis. The best attainable detection limits (3σ criterion) for bromine at 447.78, 470.49 and 734.86 nm were found to be 29.5, 7.46 and 18.4 ng ml–1, respectively, with corresponding background equivalent concentrations for bromine of 5.05, 1.72 and 2.42 µg ml–1. Typical analytical calibration graphs obtained under the optimized experimental conditions are rectilinear over approximately three orders of magnitude of concentration.