Rapid complexometric determination of mercury(II) using glutathione as a selective demasking reagent

A simple, rapid and selective complexometric method is proposed for the determination of mercury(II) in the presence of associated metal ions. Mercury(II) is first complexed with an excess of EDTA and the surplus EDTA is titrated against standard zinc sulphate solution at pH 5-6 using xylenol orange indicator. Glutathione is then added to displace EDTA from the Hg-EDTA complex quantitatively and the EDTA released is back titrated against a standard zinc sulphate solution as before. The method works well in the range 4 to 80 mg of mercury with a relative error of less than 0.30% and a coefficient of variation of not more than 0.38%. The effect of the presence of various diverse ions has been studied. The method is used for the determination of mercury(II) in its alloys and complexes.