The simultaneous spectrophotometric determination of cobalt and nickel is based on the redish brown and brown complexes formed in 30% (v/v) ethanol using 3-methyl-6-hydroxy-2`-nitro-azobenzene> Absorbances are measured at 480 and 589 nm where the molar absorptivities are 1.44 and 1.91 x 104 L mol-1 cm-1 for Co(II) and Ni(II) complexes, respectively. Sandell sensitivity for Co)II) and Ni(II) complexes are 1.7 and 2,56 ng/cm2. The system obey Beer`s law and concentration ranges as law as 8.24 and 4.12 µg/ml for cobalt and nickel, respectively. The precision, accuracy and effect of interference ions and tolerance limits have been investigated. The method has been used to determine cobalt – nickel in low alloy steel and hydrofining catalysts. .
AMSE, 52, 16–24 (1995).