Complexometric method for the determination of mercury using sodium metabisulphite as selective masking reagent

摘要

A selective complexometric method is described for the determination of mercury(II) using sodium metabisulphite as a masking reagent.An excess of EDTA is added to mercury(II) solution containing associated diverse metal ions and the surplus EDTA is back titrated at pH 5-6 (hexamine buffer) with standard zinc sulphate solution using xylenol orange as indicator.An aqueous solution of sodium metabisulphite is then added to displace EDTA selectively from Hg-EDTA complex and the released EDTA is then titrated against the same standard zinc sulphate solution.Reproducible and accurate results are obtained in the range 4-100 mg of mercury with a relative error <=0.26% and coefficient of variation <=0.40%.The method is useful for the analysis of mercury in complexes and alloy samples.