Selective extraction-spectrophotometric determination of microamounts of palladium in catalysts

A new thiosemicarbazone reagent, phthalaldehydic acid thiosemicarbazone (PAATSC) has been synthesized, and found to he a good chromogenic reagent for palladium. A method for the extraction-spectrophotometric determination of palladium is described. PAATSC-Pd(II) yellow complex was extracted from an aqueous solution (pH 4, HAc/NaAc 2 mol l(-1)) into a MIBK layer. The absorbance was measured at 355 nm and the apparent molar absorptivity (epsilon) was found to he 5.1 x 10(4) l mol(-1) cm(-1). The effect of pH, PAATSC concentration and shaking time were studied. The complex system conforms to Beer's law over the range 0.1 -2.0 mug ml(-1) palladium(II). The detection limit was 23 ng ml(-1). The: tolerance limit for many metals has been determined. The method is simple and rapid, with high sensitivity and good selectivity. Finally, the method has been applied successfully to the determination of palladium in synthetic mixtures and in the palladium-activated charcoal, used as a catalyst.