POLAROGRAPHIC-BEHAVIOR OF 2-CARBOXYBENZALDEHYDE THIOSEMICARBAZONE ANDTHE INDIRECT TRACE DETERMINATION OF PALLADIUM(II) IONS IN CATALYSTS

The electrochemical characteristics of 2-carboxybenzaldehyde thiosemic arbazone (2CBTSC) have been studied by differential pulse polarography (DPP) and cyclic voltammetry (CV) at a mercury electrode. This new th iosemicarbazone is reduced in a two-electron irreversible step at the nitrogen double bond of the side chain at pH 1.82. An anodic peak situ ated very dose to the oxidation response of mercury has been observed by DPP in neutral and alkaline media. Determination of 2CBTSC based on the reduction peak is possible in the range of 5 x 10(-8) M to 8 x 10 (-6) M, with a relative standard deviation of 2.3% in the middle of th e range and a detection limit of 7.6 x 10(-9) M (1.7 ng/mL). The decre ase in the reduction peak of the thiosemicarbazone after the addition of Pd-(II) has been used for the development of precise and sensitive amperometric determination of palladium in catalysts with an average r elative error of 1.1% and a determination limit of 6 ppb of Pd-(II) (5 .6 x 10(-7) M).