Spectrophotometric determination ot micro palladium(II) using a new reagent 2-(5-nitro-4-methyl-2-pyridylazo)-5-dimethylaminoaniline

The chromogenic reaction between a newly-synthetic reagent,2-(5-nitro-4-methyl-2-pyridylazo)-5-dimethylaminoaniline(5-NO2-4-CH3-PADMA)and palladium ? was studied.In 0.6-2.4mol/L H2SO4 medium,palladium ?reacted with 5-NO2-4-CH3-PADMA to form a green-blue complex(1∶1)whose the maximum absorption wavelength located at 621 nm.The apparent molar absorptivity was 6.05×104 L·mol-1·cm-1.Beer's law was obeyed in the range of 0-3.2μg/mL for palladium.Because the chromogenic reaction was conducted in strong acidic medium where other metal ions seldom developed color,the determination of palladium showed a high selectivity.Common metal ions as well as Rh?in 100 times,Pt?in 25 times,Ru?in 20 times,Ag in 10 times,Os?in7.5times,and Ir?in 5times did not interfere in the determination.This method was simple and rapid.It was used in the determination of micro palladium in catalyst and ores with satisfactory results.