Simultaneous determination of nickel(II) and copper(II) by second-derivative spectrophotometric method in micellar media

A second-derivative spectrophotometric method based on zero-crossing over technique is developed in simultaneous determination of copper(II) and nickel(II) ions. Methylthymol blue (MTB) as a chromogenic reagent and cetyltrimethylammonium bromide as a surfactant were used, and measurements were carried out in buffered solution at pH 6 and at a temperature of 25 degrees C. The amplitude of derivative spectra was measured at wavelengths of 631.9 and 587.7 nm for the simultaneous determination of Ni2+ and Cu2+, respectively. Linearity was obtained in the range of 0.5-5.0 mu g mL(-1) for both ions in the presence of 0.0-5.0 mu g mL(-1) of the other ion as an interfering ion. IUPAC detection limits for Cu2+ and Ni2+ ions were obtained at 0.48 and 0.43 mu g mL(-1), respectively. The proposed procedure has been applied successfully for the simultaneous determination of copper and nickel in synthetic binary mixtures and real samples.