Determination of palladium using 2-thiobarbituric acid as a releasing agent

A simple, rapid and accurate complexometric method for the determination of palladium(II) is proposed, based on the selective masking property of 2-thiobarbituric acid towards palladium(II). In the presence of diverse metal ions, palladium(II) is complexed with excess of EDTA and the surplus EDTA is backtitrated with standard zinc sulphate solution at pH 5-6 (acetic acid-sodium acetate buffer) using xylenol orange as indicator. An excess of a 0.3% solution of 2-TBA is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard zinc sulphate solution as before. Reproducible and accurate results are obtained in the concentration range 1.30-20.00 mg of palladium with relative error of 0.50% and coefficient of variation not exceeding 0.45%. The effects of diverse ions are studied. The method is used for the determination of palladium in alloys, hydrogenation catalysts and complexes.