Synthesis of 2-[2-(5-methylbenzothiazolyl)azo]-5-dimethylaminobenzoic acid and its application to the spectrophotometric determination of nickel

A new thiazolylazo reagent, 2-[2-(5-methylbenzothiazolyl)azo]-5-dimethylaminobenzoic acid (5-Me-BTAMB) was synthesized. Its chromogenic reaction with microamounts of nickel was studied in detail, and the stability constants of the complexes of Ni2+, Co2+, Fe2+, Cu2+ and Pd2+ were determined, 5-Me-BTAMB reacts with nickel(II) in the presence of sodium dodecyl sulfate to form a stable blue-violet 2:1 complex with an absorption maximum at 640 nm. The molar absorptivity of the complex is 1.32 x 10(5) l mol(-1) cm(-1). Beer's law is obeyed in the range 0-10 mu g of nickel(II) per 25 ml. The proposed method was applied to the direct determination of microamounts of nickel in aluminium alloys with satisfactory results.