Selective determination of nickel ion in river water by solvent extraction with α-furyl dioxime, followed by reversed-phase HPLC with photometric detection

A selective determination method for nickel (Ni) ion in river water has been developed by solvent extraction, followed by reversed-phase HPLC with photometric detection. The Ni(II) ion was quantitatively extracted into 4-methyl-2-pentanone over the pH range of 7.5 to 9.0 as alpha-furyl dioxime (FDO) chelate. The extracted Ni-FDO chelate was then separated on an ODS column with an eluent of methanol/water (85:15, v/v) and detected at 435 nm. Job's method suggested that the Ni-FDO chelate composition was Ni(FDO) 2 . The molar absorptivity of the Ni chelate was determined as 1.7 x 10(-4) at 435 nm. The correlation coefficients of the calibration curves obtained with 5 mL Ni standards were more than 0.999 over the range of 1 ng/mL (ppb) to 1 mu g/mL (ppm). The detection limit of the Ni ion in 5 mL water was estimated as 0.8 ppb, which corresponded to 3 times the standard deviation of the blank peak area. Relative standard deviations of peak areas (N=6) for 1 and 0.1 ppm Ni standards were less than 2%. The recoveries with a spiked river water sample for 500, 50, and 5 ppb Ni ion (N=5) were 100.51.5%, 101.21.5%, and 97.56.4%, respectively. Effects of foreign ions on the determination of 0.05 ppm Ni ion were investigated with 57 metal ions. Almost none of the ions interfered, except for Rh(III), Co(II), and Sn(II) ions.