Spectrophotometric determination of micro palladium with dibromo-o-nitroarsenazo

3-(2-arsonophenylazo)-6-(4,6-dibromo-2-nitrophenylazo)-4,5-dihydroxy-2,7-naphthalene disulfonic acid(dibromo-o-nitroarsenazo,abbreviated as DBONAA)was used in the photometric determination of palladium.In the medium of HCl and in the presence of hexadecyl trimethyl ammonium bromide,Pd(Ⅱ)reacts with DBONAA to form a stable purple-red complex(molar ratio of 1∶2),which has the maximum absorption at 566 nm,and an apparent molar absorptivity of e 566=1.79×105L·mol-1·cm-1.Beer's law is obeyed in the concentration range of 0-18 μg for palladium in 10 mL solution.The method has been applied to the determination of palladium in Pd-C catalyst and molecular sieve containning palladium with RSD of 1.42% and 0.42%,recovery of 98.4% and 97.9%,respectively.The results are agreement with those of AAS.