The H-point standard addition method (HPSAM) has been applied for simultaneous determination of Zn(II) and Ni(II) at trace levels, using Alizarin Red S (ARS) as chromogenic reagent. Both Ni(II) and Zn(II) form red colored complex with Alizarin red S at pH 7.0 which are soluble in triton x-100. Zn(II) and Ni(II) have been determined simultaneously in the concentration range of 0.320-4.55 µg/mL and 0.293-4.676 µg/mL respectively with satisfactory accuracy and precision. The results of applying H-point standard addition method show that Zn(II) and Ni(II) ions can be determined simultaneously with concentration ratio of 15:1 and 1:16 of Zn(II) to Ni(II). This method is based on the difference in the absorbance of Zn(II) and Ni(II) - ARS complexes at pH 7.0 using different wavelength pairs.
HPSAM, Zinc, Nickel, Simultaneous determination and triton x-100