Extraction-atomic absorption spectrophotometric determination of palladium as its anionic complex with a sulfonated azo dye

The use of 3-hydroxy-4-( 1 H -tetrazol-5-ylazo)-2,7- naphthalenedlsulfonlc acid (T-azo-R) as a complexlng agent for the separatlon of palladium from rhodium, platinum, or iridium by solvent extraction in the presence of benzalkonium chloride (BACl) has been investlgated. After reextraction with perchlorlc acid from organic to aqueous phase, palladium can be determined by alr-acetylene flame atomic absorptlon spectrometry (FAAS), by means of a calibration curve prepared with commerclal standard solutions. The mutual or matrix interferences, whlch make difficult the direct FAAS determlnatlon of palladium in the presence of other platinum group metals or even of some other common ions, are completely overcome. At the same time, preconcentrations of at least a factor of 50 can be obtained. The method has been applied to the determinatlon of palladium and rhodium content in two pharmaceutlcai processing sludges.