Spectrophotometric determination of micro platinum(II) with dibromo-o-nitro-arsenazo

The color reaction of 3-[(2-arsonophenyl)azo]-6-[(4,6-dibromo-2-nitrophenyl)azo]-4,5-dihydroxynaphthalene-2,7-disulfonic(abbreviated as DBONAA,dibromo-o-nitro-arsenazo)with platinum(Ⅱ)was studied in the presence of cetyl trimethylammonium bromide(CTMAB),and a new spectrophotometric method for the determination of micro platinum was established.The experimental results show that platinum(Ⅱ) reacts with DBONAA to form a stable mauve complex with molar ratio of 1∶3 in HAc-NaAc buffer medium at pH 6.5.The maximum absorption wavelength and apparent molar absorptivity are 526 nm and 1.12×105 L·mol-1·cm-1,respectively.Beer′s law is obeyed in the range of 0.03-14 μg in 10 mL solution for Pt(Ⅱ).The method has been applied to the determination of platinum in the platinum catalyst and platinum concentrate with recovery of 98.1%,99.4% and relative standard deviation of 0.23%,0.83%.