A novel micellar sensitized spectrophotometric method has been developed in the present work for the determination of nickel in varying geological matrices such as aluminum alloys, stainless steel, manganese nodule and others. The method utilizes the reaction of 5- (2’– carboxyphenyl) azoxine with nickel in aqueous medium at pH 5.2-6.1 to form a winered colored complex. The reaction is sensitized by Triton X-100, a non-ionic surfactant. Triton X-100, micellar sensitization of the reaction results in five times enhanced molar absorptivity enabling the determination of an amount as low as 1 ppm of nickel in rock samples within a relative standard deviation of ±1.2% and enhanced stability of the complex from 4 hours to at least 40 hours. Extraction of the complex is avoided making the procedure simple, rapid and easy in operation. The molar absorptivity and Sandell’s sensitivity of the complex are 1.15.105 1.mol-1 .cm-1 and 0.51 ng.cm-2 at λmax 557nm, respectively. The limit of determination 5 ppb in solution is far better than the detection limit by ICPOES (10 ppb) at the most favored nickel line 231.60 nm. The method was applied to the determination of nickel in aluminum alloys, stainless steel, manganese nodule and other geological materials.

Keywords : Spectrophotometry, nickel, triton X-100, 5- (2’ – carboxyphenyl) azoxine, micellar sensitization, aluminum alloys, stainless steel, manganese nodule, geological samples, ICP-OES, determination limit.