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H-point Standard Addition Method for Simultaneous Determination of Cobalt(II) and Zinc(II) Ions

H.R. Pouretedal^a,* and M. Asefi^b

^aChemistry Department, Malek-ashtar University of Technology, Shahin-shahr, I.R. Iran
^bIslamic Azad University, Shahreza Branch, I.R. Iran

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of zinc(II) and cobalt(II). This method is based on the difference in the absorbance of methylthymol blue complexes of Zn(II) and Co(II) at pH 6 using different wavelength pairs. The results showed that Zn(II) and Co(II) can be determined simultaneously with concentration ratios of 20:1 and 1:7.5. Under working conditions, the proposed method was successfully applied to the simultaneous determination of zinc and cobalt in synthetic, drinking water and vitamin samples.

Keywords: H-point standard addition method, Zinc, Cobalt, Methylthymol blue