GLUTATHIONE AS A SELECTIVE DEMASKING AGENT FOR THE COMPLEXOMETRIC DETERMINATION OF THALLIUM

A simple, rapid and accurate complexometric method is proposed for the determination of thallium,glutathione being used as releasing agent. Thallium(III) along with the associated metal ions in a given sample solution is first complexed with an excess of EDTA and the surplus EDTA is titrated with zinc sulphate solution at pH 5 -6 (hexamine buffer) using xylenol orange as indicator. EDTA equivalent to thallium is then released selectively with glutathione and is again titrated as above. The interference of various diverse ions has been studied. Reproducible and accurate results are obtained in the range 4-100mg of thallium with relative errors ± 0.3% and coefficient of variation ≤0.36%. The method is applied to the determination of thallium in its complexes and synthetic alloy compositions.