Highly Selective Spectrophotometric Determination of Trace Palladium(II) Using a New Reagent 5-(5-Iodine-2-pyridylazo)-2,4-diaminotoluene

A new reagent,5-(5-iodine-2-pyridylazo)-2,4-diaminotoluene(5-I-PADAT),was recommended for the determination of palladium.In strong acidic media,palladium(Ⅱ) could react with 5-I-PADAT at room temperature to form a 1∶1 stable blue-purple complex with the maximum absorption wavelength located at 583 nm.The apparent molar absorptivity was 7.2×104 L·mol-1·cm-1 in 1.2 mol·L-1 perchloric acid.Beer's law was obeyed in the range of 0 ～ 1.0 μg·mL-1 for palladium.The common metal ions did not interfere with the determination of palladium.The method was simple and rapid,with very high selecitivity and good sensitivity.It was used in the determination of palladium in molecular sieve,alloy and ore with satisfactory results.