Complex formation of the new reagent 5-(6-methoxy-2-benzothiazoleazo)-8-aminoquinoline with cobalt and nickel for their sensitive spectrophotometric detection Original Research Article

The synthesis, characteristics and analytical reactions of a new reagent 5-(6-methoxy-2-benzothiazoleazo)-8-aminoquinoline (MBTAQ) with cobalt and nickel are described, and sensitive spectrophotometric methods for the determination of cobalt and nickel by this reagent have been developed. In the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) and borax buffer solution, cobalt and nickel form blue coloured, 1 : 2 and 1 : 3 (metal : ligand) complexes with MBTAQ, respectively. The apparent molar absorptivities are 1.15 × 105 (Co) and 1.28 × 105 (Ni) l mol−1 cm−1 at 655 and 623 nm. The methods obey Beerʹs law for 0–0.40 μg ml−1 of cobalt and 0–0.32 μg ml−1 of nickel and the detection limit are 0.00050 and 0.00045 μg ml−1. The relative standard deviations for measurement of 0.24 μg ml−1 cobalt and of 0.20 μg ml−1 nickel are 0.7% and 1.1% (n = 6), respectively. The methods were successfully used to determine trace amounts of cobalt in drainage sediment and trace amounts of nickel in aluminium alloy.