EXTRACTION AND SPECTROPHOTOMETRIC DETERMINATION OF PD(II) WITH TRAHYDRO-3,3,4A-TRIMETHYL-7-(SUBSTITUTED)-PYRIMIDO (1,6-A)BENZIMIDAZOLE-1-THIOL (PBT)

A method for the extraction-spectrophotometric determination of pallad ium with (substituted)-pyrimido(1,6-a)benzimidazole-1-thiol (PET) is d escribed. PBT-Pd(II) complex is extracted from an acidic aqueous solut ion (0.01-0.5M HClO4) into a chloroform layer. The absorbance is measu red at 438 nm and the molar absorptivity found to be 1.033 x 10(4)M(-1 ) cm(-1). The complex system conforms to Beer's law over the range 1.9 -28.5 mu g/ml palladium(II). The effects cm of pH (2-6), HClO4 concent ration, PBT concentration and shaking time were studied. The ratio of metal ion to ligand molecules in the coloured complex was found to be 1:4. The tolerance limit for many metals have been determined. Finally , the method has been applied successfully to the determination of pal ladium in synthetic mixtures and in the standard palladium carbon powd er (palladium catalyst).