SELECTIVE DETERMINATION OF NICKEL ION BY SOLVENT EXTRACTION AS o-SALICYLIDENEAMINOPHENOL CHELATE FOLLOWED BY LIGAND EXCHANGE AND REVERSED-PHASE HPLC WITH PHOTOMETRIC DETECTION

Nickel ion was extracted into mixed solvents of 4-methyl-2-pentanone and 1-decanol (3 : 1, v/v) as o-salicylideneaminophenol (SAPH) chelate at pH 9. Organic layers of 5 μL and 10 μL of 10 mmol/L hexamethyleneammonium hexamethylenedithiocarbamate (HMA-HMDC) were injected into a C18 column. The Ni-SAPH chelate was converted to Ni-HMDC chelate on the column and detected at 325 nm. The correlation coefficient of the calibration curves obtained with 5 mL of nickel solution was more than 0.999 over the range of 10 ng/mL to 10 μg/mL. Recovery tests were carried out with snow samples and nickel standard solutions. The recoveries for 500 ng/mL and 50 ng/mL Ni ion were 105% and 95%, respectively. Linearity of the calibration curves and recovery were more excellent than those of ICP-AES. Effects of foreign ions on the method were investigated with 49 metal ions. Almost all ions did not interfere except for Rh(III) and Mn(II).