Extraction-spectrophotometric determination of nickel(II) with diammonium ethylene-bis-dithiocarbamate

Diammonium ethylene-bis-dithiocarbamate (DETC) reacts with nickel (II) and forms a water-insoluble greenish brown complex in aqueous solution at pH 6.5, which can be extracted with MIBK containing 1 v/v % TBP. The extraction-spectrophotometric method for the determination of nickel (II) based on this reaction was studied. The recommended procedure is as follows : To a sample solution (4 cm3) containing (0.26.0) μg, was added 8 cm3 of Britton and Robinson buffer (pH 6.5), and the mixture was heated for 10 min at 50°C. The resultant solution was mixed with 2 cm3 of 0.5 % DETC aqueous solution and heated for 25 min at 50°C. After cooling for 3 min in ice-water, nickel (II) in the solution was extracted with 4 cm3 of MIBK containing 1 v/v% TBP by shaking for 2.5 min. The absorbance of the extract was measured at 385 nm against the reagent blank. The apparent molar absorption coefficient of the complex was 3.65 × 104 dm3 mol -1 cm-1, and the Beer's law obeyed the concentration range from 0.05 to 1.50 μg cm-3 of nickel (II). The molar ratio of nickel (II) to DETC in the complex was estimated to be 1 : 2 by the continuous variation method. Various metal ions, such as cobalt (II), copper (II), iron (II) and (III), lead (II), molybdenum (VI), palladium (II), strontium (II), zinc (II), interfered. These interfering metal ions could be removed by extraction of nickel (II) as dimethylglyoximate complex with chloroform.