Spectrophotometric determination of cobalt in aluminium alloy with picramazochrom

A new color reagent picramazochrom,which is very sensitive and excellent selective is adopted to establish a spectrophotometric determination of microcobalt in aluminium alloy samples.In NH_3·H_2O-NH_4Cl buffer solution at pH 11 and in the presence of NaF,the maximum absorption wavelength of the complex formed by cobalt and picramazochrom is at 650 nm and an apparent molar absorptivity is 3.1×10~4 L·mol~(-1)·cm~(-1). Beer's law is obeyed in the range of 0-50 μg/25mL for Co?.The method has been successfully applied to the determination of cobalt in aluminium alloy samples.The relative standard deviation is 2.2%,and the recovery is 95.3% and 100.8%,respectively.The results of the experiment are very satisfactory.