H–Point Standard Addition Method for Simultaneous Spectrophotometric Determination of Cobalt(II) and Nickel(II)

The H-point standard addition method (HPSAM) was applied for the simultaneous spectrophotometric determination of cobalt(II) and nickel(II) in range 10-5 to 10-4 mol/ L. The new synthesized 2, 4-dihydroxybenzaldehyde thiosemicarbazone (DHBATSC) was used as a chromogenic reagent in aqueous Triton X-100 micellar medium and at pH 7. The absorbance at the selected wavelength pair, 463 and 500 nm were monitored with the addition of standard solution of cobalt. The results obtained showed that Co(II) and Ni(II) can be determined simultaneously with concentration ratios of 5:1 to 1:5 (wt/wt). The R.S.D for a solution containing Co(II) and Ni(II) both at 5.0 × 10-5 M were 1.86% and 4.4% respectively. The effect of diverse ions on the determination of cobalt(II) and nickel (II) were also investigated. The proposed method was successfully applied to the simultaneous determination of cobalt(II) and nickel(II) in synthetically spiked mixtures and cobalt(II) in vitamin B12 sample.